Archive for the ‘Environmental Toxins’ Category

Biodegradation of synthetic polymers in soils: Tracking carbon into CO2 and microbial biomass


Plastic materials are widely used in agricultural applications to achieve food security for the growing world population. The use of biodegradable instead of nonbiodegradable polymers in single-use agricultural applications, including plastic mulching, promises to reduce plastic accumulation in the environment. We present a novel approach that allows tracking of carbon from biodegradable polymers into CO2 and microbial biomass. The approach is based on 13C-labeled polymers and on isotope-specific analytical methods, including nanoscale secondary ion mass spectrometry (NanoSIMS). Our results unequivocally demonstrate the biodegradability of poly(butylene adipate-co-terephthalate) (PBAT), an important polyester used in agriculture, in soil. Carbon from each monomer unit of PBAT was used by soil microorganisms, including filamentous fungi, to gain energy and to form biomass. This work advances both our conceptual understanding of polymer biodegradation and the methodological capabilities to assess this process in natural and engineered environments.


Modern agriculture heavily relies on the use of plastic materials in various applications, a practice coined plasticulture. Mulching with plastic films is a major application with a global market volume of approximately 2 × 106 tons per year (1). Mulch films are placed onto agricultural soils to improve conditions for plant growth while lowering consumption of water, herbicides, and fertilizer and also minimizing soil erosion (1, 2). Because of these benefits, mulching with plastic films helps to secure food for the growing world population. However, mulch films are commonly composed of nonbiodegradable polyethylene and, therefore, accumulate in agricultural soils and surrounding receiving environments if incompletely retrieved after use. These accumulations have negative ecologic and economic impacts, including decreased soil productivity (35). A promising strategy to overcome these risks is to use mulch films composed of polymers that biodegrade in soils (1, 68).

Biodegradation of polymers requires microorganisms to metabolize all organic components of the polymer. Biodegradation in soil involves several key steps (Fig. 1): (i) colonization of the polymer surface by microorganisms, (ii) secretion of extracellular microbial enzymes that depolymerize the polymer into low–molecular weight compounds, and (iii) microbial uptake and utilization of these compounds, incorporating polymer carbon into biomass or releasing it as CO2 (9).

Fig. 1 Key steps in the biodegradation of polymers in soils.

Microorganisms colonize the polymer surface and secrete extracellular enzymes that depolymerize the polymer. The formed low–molecular weight hydrolysis products are taken up by the microorganisms and used both for energy production, resulting in the formation of CO2, and for the synthesis of cellular structures and macromolecules, resulting in incorporation of polymer-derived carbon into the microbial biomass. The boxes on the right depict the analytical methods we used to study these steps. NMR, nuclear magnetic resonance.

Fig. 1 Key steps in the biodegradation of polymers in soils.Microorganisms colonize the polymer surface and secrete extracellular enzymes that depolymerize the polymer. The formed low–molecular weight hydrolysis products are taken up by the microorganisms and used both for energy production, resulting in the formation of CO2, and for the synthesis of cellular structures and macromolecules, resulting in incorporation of polymer-derived carbon into the microbial biomass. The boxes on the right depict the analytical methods we used to study these steps. NMR, nuclear magnetic resonance.Here, we examined each of the above steps for poly(butylene adipate-co-terephthalate) (PBAT), an aliphatic-aromatic statistical copolyester of large importance in the market of biodegradable mulch films (7). While previous studies provided indirect indications for PBAT biodegradation in soils based on determining PBAT mass loss and changes in its physicochemical properties (1012), we here use a novel workflow using stable carbon isotope-labeled PBAT to directly and unequivocally demonstrate its biodegradation in soil (table S1). This workflow included incubation of 13C-labeled polymer films in soil with continuous quantification of polymer-derived 13CO2 by isotope-specific cavity ring-down spectroscopy (CRDS) (13). The use of 13C-labeled polymers allowed us to distinguish polymer-derived CO2 from CO2formed by soil organic matter mineralization. After incubation, we imaged the polymer film surfaces using scanning electron microscopy (SEM) and demonstrated the incorporation of polymer-derived 13C into the biomass of film-colonizing microorganisms using element-specific, isotope-selective nanoscale secondary ion mass spectrometry (NanoSIMS) (14). We studied three PBAT variants that had similar physicochemical properties and comparable total 13C contents, but varied in the monomer that contained the 13C-label [that is, butanediol (P*BAT), adipate (PB*AT), or terephthalate (PBA*T)] (Fig. 2A and table S2). The use of these variants allowed us to follow biodegradation of all PBAT building blocks. The presented workflow is a novel approach to study the fundamental steps in polymer biodegradation in complex systems (1517).


This work presents an experimental approach to study polymer biodegradation in soils and to assess the key steps involved in this process: microbial polymer colonization, enzymatic depolymerization on the polymer surface, and microbial uptake and utilization of the released low–molecular weight compounds. Central to the approach is the use of polymer variants that are 13C-labeled in all monomer units of the polymer, thereby allowing us to assess whether all organic components of the polymer material are used by soil microorganisms. The label further allows tracing of polymer-derived carbon into both CO2 and microbial biomass. Using this approach, we demonstrate here the biodegradability of PBAT in soil. Biodegradability renders PBAT a more environmentally friendly alternative to persistent polymer materials for use in plasticulture, including single-use applications such as plastic mulching. Our results further imply that incorporation of polymer-derived carbon into microbial biomass needs to be taken into consideration in regulatory guidelines for determining biodegradability of polymers. Currently, these guidelines are solely based on extents of CO2 formation. Furthermore, the finding of subcellular structures within PBAT-colonizing fungi highly enriched in polymer-derived carbon might represent compartments in which carbon is stored (for example, in the form of neutral lipids) when fungi are limited by the availability of nutrients other than carbon (22). These limitations are plausible for microorganisms growing on PBAT and other polymers that do not contain nitrogen and phosphorous. If these limitations occur, increasing the availability of soil nutrients to microorganisms colonizing the polymer surface is expected to enhance polymer biodegradation.

This work demonstrates PBAT biodegradation in a selected agricultural soil over 6 weeks of incubation. Future studies extending on this work will need to assess variations in the rates and extents of PBAT mineralization among different agricultural soils, also over longer-time incubations. Furthermore, we propose studies that are directed toward identifying soil microorganisms that are actively involved in PBAT biodegradation. While the NanoSIMS-based approach presented here allows us to unambiguously demonstrate incorporation of polyester carbon into soil microbial biomass, it is not a high-throughput technique. Alternative approaches, including the extraction of targeted biomolecules from soils containing 13C-labeled polymers followed by quantifying the 13C contents in the extracted molecules, will allow us to analyze larger sample sets and thereby to systematically determine potential variations among soil microorganisms in the extent to which they incorporate polymer-derived carbon into their biomass.


Experimental design

The objective of this study was to develop an experimental approach to demonstrate biodegradation of PBAT in an agricultural soil. As biodegradation includes mineralization of PBAT carbon to CO2, as well as the incorporation of PBAT-derived carbon into the biomass of soil microorganisms, we addressed both of these processes in controlled laboratory experiments. We followed PBAT mineralization during soil incubation using an isotope-specific CRDS for the quantification of formed CO2. For each of the three PBAT variants, we simultaneously incubated seven films in one incubation bottle filled with soil to allow precise quantification of PBAT mineralization to CO2. The soil incubations were terminated after 6 weeks (that is, when approximately 10% of the PBAT carbon had been mineralized) to ensure that PBAT films were still intact for the subsequent imaging analyses. We revealed incorporation of PBAT-derived carbon into biomass using NanoSIMS, which enabled identification of subcellular features and determination of the carbon isotope composition of the PBAT film surface and the colonizing microorganisms at submicrometer spatial resolution. The low throughput of this high-end topochemical analysis technique constrained the number of collected images for soil-incubated films to two images for each of the three PBAT variants including replicate films. We note that we did not exclude any data or outliers from our analysis.

Polyesters, monomers, soil, and enzymes

Polyesters were provided by BASF SE and synthesized as previously described (23, 24). The physicochemical properties of the polyesters are listed in table S2. To obtain similar 13C contents for the three PBAT variants (that is, PB*AT, P*BAT, and PBA*T), synthesis of all variants was performed with defined ratios of labeled to unlabeled monomers. The three PBAT variants were free of chemical additives.

The 13C-labeled monomers 1,6-13C2-adipate and 13C4-butanediol used for PBAT synthesis and for soil incubation studies were purchased from Sigma, with more than 99% of the indicated positions in the monomer containing 13C. We obtained 1-13C1-terephthalate from dimethyl 1-13C-terephthalate purchased from Sigma. To obtain the free diacid, we dissolved dimethyl 1-13C-terephthalate in 2:1 water/tetrahydrofuran (5 mg in 2.4 ml), added 25 μl of a sodium hydroxide solution [37% (w/w)], and stirred the solution at room temperature for 2 hours. The solvent was then carefully removed under reduced pressure to obtain the hydrolysis product 1-13C1-terephthalate (confirmed by 1H NMR).

For PBAT and monomer incubations in soils under controlled laboratory conditions, we used agricultural soils from the agricultural center Limburgerhof (Rhineland-Palatinate, Germany). Physicochemical properties of the soils are provided in table S1. The soils were air-dried to a humidity of 12% of the maximum water-holding capacity of the soil, passed through a 2-mm sieve, and stored in the dark at 4°C for 12 months before use in the incubation experiments.

R. oryzae lipase was purchased as a powder from Sigma (catalog no. 80612). FsC was obtained as a solution from ChiralVision B.V. (Novozym 51032). Stock solutions of both enzymes in water were stored at −20°C.

Preparation of PBAT films and soils for incubation experiments

We prepared two sets of solvent-cast PBAT films that differed in the way that the PBAT films were attached to the silicon wafer substrates. For the first set, we solvent-cast PBAT films by adding three times 15 μl of a PBAT solution in chloroform [concentration, 5% (w/w)] onto a square-cut antimony-doped silicon wafer platelet (7.1 mm × 7.1 mm × 0.75 mm, Active Business Company). In between the additions of the polymer solutions, we allow the chloroform to evaporate. This procedure resulted in a PBAT mass of approximately 3 mg per wafer. Before incubation in soil, the solvent-cast polyester films were stored in the dark at room temperature for 1 week to ensure complete evaporation of the solvent (chloroform). PBAT variants from this first set were used for PBAT mineralization experiments (Fig. 2B), SEM imaging (Fig. 2C), and NanoSIMS imaging (Figs. 3 and 4 and fig. S8).

For the second set of PBAT films, we pretreated the silicon wafer platelets with Vectabond (Vector Laboratories, catalog no. SP-1800) before solvent casting of the polyester films. This second set of PBAT films was included to test whether the adhesion of the PBAT to the Si surface can be improved by this modified protocol. For the pretreatment, we exposed the wafers to a 1:50 diluted solution of Vectabond in acetone, subsequently dipped them into MilliQ water (Barnstead Nanopure Diamond), and dried them in a stream of N2. PBAT variants from this set were used only to determine PBAT mineralization (fig. S1), but not for SEM and NanoSIMS imaging.

We prepared the soil for PBAT incubations by adding MilliQ water to the soil to adjust its water content to 47% of its maximum water-holding capacity. We subsequently transferred 60 g of the soil into each of the incubation vessels (100-ml glass Schott bottles). We prepared a total of nine incubation bottles in three sets of three bottles (see below). The soils were then preincubated at 25°C in the dark for 1 week.

After soil preincubation, we transferred the wafers carrying the solvent-cast polyester films into the soils in the incubation bottles. We added seven wafers to each incubation bottle. The wafers were spaced apart by at least 1 cm. All wafers were positioned upright in the soil. The three bottles of the first set each contained films of one of the three differently labeled PBAT variants obtained by direct solvent casting. The three bottles of the second set were identical to the first set except for the wafers, which were pretreated with Vectabond before solvent casting. The three bottles in the third set served as controls and contained soil but no PBAT films. All bottles were incubated for 6 weeks at 25°C in the dark. We note that our study therefore does not address potential effects of ultraviolet irradiation–induced changes in the structure of PBAT on its biodegradability. Over the course of the incubation, we gravimetrically determined the water content of the soils at defined time intervals. To sustain a constant soil water content, amounts of water that were lost from the soil through evaporation were replenished by adding corresponding amounts of MilliQ water.

Preparation and SEM imaging of soil-incubated PBAT films

After 6 weeks of incubation in soil, we carefully removed the silicon wafers carrying the PBAT films from the soils. To chemically fix the cells attached to the surfaces of the PBAT films, we directly transferred the films into a freshly prepared fixation solution (pH 7.4) containing glutaraldehyde (2.5%), sodium cacodylate (0.1 M), sodium chloride (0.1 M), potassium chloride (3 mM), and sodium phosphate (0.1 M). The films were exposed to this solution for 20 min at 25°C and subsequently transferred to a solution of OsO4 in MilliQ water (1%) for 30 min of exposure on ice. Finally, we dehydrated the films in a series of water/ethanol solutions of increasing concentrations (70%, 5 min; 95%, 15 min; 100%, 2 × 20 min), followed by critical point drying of the samples with liquid CO2 (Baltec CPD 030). Critical point drying resulted in detachment of the PBAT films from the wafer. To reattach the films to the wafers for further analyses, we used a double-sided adhesive, electrically conducting carbon tape (Ted Pella, product no. 16084-1). Directly after mounting the films onto the wafers with carbon tape, thin films of platinum (thickness, 10 nm) were deposited on the samples using a sputter coater (Baltec SCD 500). SEM was conducted on a Zeiss Supra 50 VP. Imaging was performed with a secondary electron detector at a working distance of 4.0 mm and an electron high tension of 5.0 kV. These films were also used for NanoSIMS analysis (see below).

PBAT films from the second set, for which wafers were pretreated with Vectabond before solvent casting of PBAT (see above), also detached from the wafers. We decided to reject further analysis of these films (that is, SEM and NanoSIMS).

PBAT film imaging by NanoSIMS

NanoSIMS measurements were performed on a NanoSIMS NS50L (Cameca) at the Large-Instrument Facility for Advanced Isotope Research (University of Vienna). Before data acquisition, analysis areas were presputtered by scanning of a high-intensity, slightly defocused Cs+ ion beam (beam current, 400 pA; spot size, approximately 2 μm). To avoid crater edge effects, scanning during presputtering was conducted over square-sized areas with an edge length exceeding the frame size of the subsequently recorded images by at least 15 μm. Every data set acquired on the soil-incubated polymer films contains image data recorded from (at least) two distinct depth levels, accessed by sequential presputtering with Cs+ ion fluences of 5.0 × 1016 and 2.0 × 1017 ions/cm2, respectively. Application of the lower ion dose density enabled sampling of all cells within the analysis areas, irrespective of their size and/or morphology, whereas the extended presputtering allowed us to gain insight into cellular features contained within the lumen of bulky cells such as fungal hyphae (see, for example, Fig. 4).

Imaging was conducted by sequential scanning of a finely focused Cs+ primary ion beam (2-pA beam current) over areas ranging from 45 × 45 μm2 to 70 × 70 μm2 at a physical resolution of approximately 70 nm (that is, probe size) and an image resolution of 512 × 512 pixels. If not stated otherwise, images were acquired as multilayer stacks with a per-pixel dwell time of 1.5 ms per cycle. 12C, 13C, 12C12C, 12C13C, 12C14N, 31P, and 32S secondary ions as well as secondary electrons were simultaneously detected, and the mass spectrometer was tuned for achieving a mass resolving power of >9.000 (according to Cameca’s definition) for detection of C2 and CN secondary ions. Image data were analyzed with the ImageJ plugin OpenMIMS, developed by the Center for NanoImaging (27). Secondary ion signal intensities were corrected for detector dead time (44 ns) and quasi-simultaneous arrival (QSA) of secondary ions. Both corrections were performed on a per-pixel basis. QSA sensitivity factors (“beta values”) were obtained from measurements on dried yeast cells, yielding 1.1, 1.06, and 1.05 for C, C2, and CN secondary ions, respectively. Before stack accumulation, images were corrected for positional variations originating from primary ion beam and/or sample stage drift. ROIs were manually defined on the basis of 12C14N secondary ion signal intensity distribution images and cross-checked by the topographical/morphological appearance indicated in the simultaneously recorded secondary electron images (see fig. S10). While each cell from unicellular organisms was assigned to an individual ROI, image regions within the polyester surfaces and hyphae were segmented into multiple ROIs. Throughout the article, the carbon isotope composition is displayed as the 13C/(12C + 13C) isotope fraction, given in at%, calculated from the C and C2 secondary ion signal intensities via 13C/(12C + 13C) and 13C12C/(2⋅12C12C + 13C12C), respectively. Owing to superior counting statistics, all carbon isotope composition data shown in the article were inferred from C2signal intensities. We note that we did not observe any significant differences between 13C content values inferred from C2 signal intensities versus C signal intensities. For the line scan analyses displayed in Fig. 4, C2 normalized C14N signal intensities were used as an indicator of the relative nitrogen content {calculated via [12C14N (1 + 13C/12C)]/[12C13C + 12C2 (1 + (13C/12C)2)], whereby the term 13C/12C refers to the 13C-to-12C isotope ratio, calculated from the C2 signal intensities via 13C12C/(2⋅12C12C)}. This quantity formally refers to the relative nitrogen-to-carbon elemental ratio and was used in favor of the relative nitrogen concentration, which is inferable from C normalized C14N signal intensities, to minimize artifacts arising from the considerable topography within the areas of the fungal hyphae (28).


Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/7/eaas9024/DC1

Supplementary Materials and Methods

Fig. S1. Mineralization of PBAT films.

Fig. S2. NMR analysis of enzymatic hydrolysis products of PBAT films I.

Fig. S3. NMR spectra of terephthalate, adipate, and butanediol.

Fig. S4. NMR analysis of enzymatic hydrolysis products of PBAT films II.

Fig. S5. NMR analysis of enzymatic hydrolysis products of PBAT films III.

Fig. S6. NMR analysis of enzymatic hydrolysis products of PBAT films IV.

Fig. S7. Mineralization of terephthalate, adipate, and butanediol.

Fig. S8. NanoSIMS analysis of PBAT films after soil incubation I.

Fig. S9. Control experiment for NanoSIMS analysis I.

Fig. S10. Definition of ROIs.

Fig. S11. Control experiment for NanoSIMS analysis II.

Fig. S12. NanoSIMS analysis of PBAT films after soil incubation II.

Table S1. Soil characterization.

Table S2. Characterization of PBAT variants.

Supplementary Appendix. Calculations of the carryover during NanoSIMS measurements.

References (2933)

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial license, which permits use, distribution, and reproduction in any medium, so long as the resultant use is not for commercial advantage and provided the original work is properly cited.

Acknowledgments: We thank S. Probst, M. Jaggi, and F. Strasser for their help with growing E. coli, performing IRMS measurements, and NanoSIMS control sample preparation and data analysis, respectively. Funding: M.T.Z., T.F.N., R.B., H.-P.E.K., K.M., and M.S. thank the Joint Research Network on Advanced Materials and Systems of BASF SE and ETH Zürich for scientific and financial support. M.W. and A.S. were supported by the European Research Council Advanced Grant project NITRICARE 294343. D.W. was supported by the European Research Council Starting Grant project DormantMicrobes 636928. SEM imaging was performed at the Center for Microscopy, University of Zurich. Author contributions: M.T.Z., A.S., D.W., H.-P.E.K., K.M., and M.S. designed the study. M.T.Z., A.S., T.F.N., and R.B. performed experiments. All authors contributed to the writing of the manuscript. Competing interests: The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate our conclusions are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.

  • Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).




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FDA Announcement – Protecting Public Health by Strategic Implementation of Prevention-Oriented Food Safety Standards

The FDA Food Safety Modernization Act (FSMA) gives FDA a new public health mandate. It directs FDA to establish standards for adoption of modern food safety prevention practices by those who grow, process, transport, and store food. It also gives FDA new mandates, authorities and oversight tools aimed at providing solid assurances that those practices are being carried out by the food industry on a consistent, on-going basis.  FDA will fulfill the vision of FSMA and strengthen food safety protection by applying the principles outlined here across the entire food safety program, while adapting them to the specific challenges posed by implementation of preventive controls, produce safety standards, and FSMA’s new import system. (more…)

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Here’s an article from our local paper on contaminated drinking water around the state and the country.  Scroll down to the EWG “data base” and click.  Enter your zip code and it will tell you how healthy or contaminated your drinking water is.  And will list the chemicals.  Was rather shocked to see that my area had 6 contaminants listed … all cancer-causing …
Next thing I’ll be doing is to look into the type of water filter I have (I bought a pretty good one a year ago), and see if it filters out the chemicals listed.

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Household Chemical Exposures and the Risk of Canine Malignant Lymphoma, a Model for Human Non-Hodgkin’s Lymphoma

Biki B. Takashima-Uebelhoer,1 Lisa G. Barber,2 Sofija E. Zagarins,3 Elizabeth Procter-Gray,4 Audra L. Gollenberg,5Antony S. Moore,2,6 and Elizabeth R. Bertone-Johnson1,2


Epidemiologic studies of companion animals offer an important opportunity to identify risk factors for cancers in animals and humans. Canine malignant lymphoma (CML) has been established as a model for non-Hodgkin’s lymphoma (NHL). Previous studies have suggested that exposure to environmental chemicals may relate to development of CML..

Conclusions. In summary, findings of this study suggest that exposure to certain types of lawn care chemicals may increase the risk of malignant lymphoma in dogs. Additional studies are needed to further evaluate the effects of specific chemical components of lawn care products on risk of canine malignant lymphoma, and may potentially contribute to human NHL as well.

Results suggest that use of some lawn care chemicals may increase the risk of CML. Additional analyses are needed to evaluate whether specific chemicals in these products may be related to risk of CML, and perhaps to human NHL as well.

Keywords: Lymphoma, Non-Hodgkin, Dogs, Epidemiology, Case-Control Studies, Specialty Uses of Chemicals


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Inhalation of Pesticide Residues

Very little peer-reviewed research has been published on the health and safety risks associated with pes cides on dried cannabis. How- ever, the tests that have been performed show cause for significant consumer concern, particularly medical patients or those with elevated risk factors. http://www.beyondpesticides.org


As states legalize the produc on of cannabis (marijuana) for medical and recrea onal purposes, regula ons governing its cul va- on may allow the applica on of pes cides untested for use in the plant’s produc on, raising safety issues for pa ents and con- sumers. In the absence of federal regula ons governing pes cides in cannabis produc on, the use of pes cides not registered by the U.S. Environmental Protec on Agency (EPA)† is understood to be illegal. Several states have codi ed this understanding by adop ng policies that prohibit all federally registered pes cides. Other states have taken the posi on that state policy is unnecessary, since EPA has not registered any pes cides for cannabis produc on and registered pes cide use is illegal. A review of state laws conducted by Beyond Pes cides nds a patchwork of regula ons with varying degrees of protec on for consumers and the environment.

Is the public adequately protected from pes cide use in cannabis produc on and residues on the crop that could be inhaled, ingested, or absorbed? Are states doing an adequate job to enforce the law?

The range of state standards and the lack of a federal role in establishing which pes cides are allowed for use in the plant’s produc on raises cri cal concerns related to: (i) exposure from inhala on, inges on, or absorp on of pes cide residues on the crop; (ii) exposure to workers cul va ng the plant; and (iii) environmental contamina on and wildlife e ects. Since the federal government classi es cannabis as a Schedule 1 narco c, EPA does not establish restric ons for pes cides used in cannabis produc on, or tolerances (or exemp ons from tolerances) for allowable pes cide residues on cannabis. As a result, EPA-permi ed pes cide labels do not contain allowances for pes cide use in cannabis produc on. That might seem to be the end of the story, but, in fact, states have sought to address this issue and in some cases a rm the prohibi on (either with clear prohibitory language or through regulatory silence with an explanatory note on pes cide prohibi on), allow certain toxic pes cides with generalized label language that are exempt from tolerances, or permit pes cides that EPA has determined are exempt from registra on.

In this context, toxic pes cide use in cannabis cul va on ranges from allowances of pre-plant herbicides to restric ons that only allow organic management systems without any synthe c materials. While much of the focus is on residues in inhaled, ingested, or absorbed cannabis, environmental impacts associated with growing prac ces are mostly not addressed.

*Drew Toher contributed research and analysis to this inves ga ve report.

†For purposes of this review, federally registered pes cides are dis nguished from pes cide exempt from federal registra on under Sec on 25(b) of the Federal In- sec cide, Fungicide and Roden cide Act (FIFRA). Registered pes cides are subject to EPA-required tes ng by the manufacturer for health and environmental e ects, while 25(b) pes cides exempt from registra on are waived from data requirements because they have been determined to contain ingredients iden ed as harmless.

Page 14 Pesticides and You
A quarterly publication of Beyond Pesticides

State of Cannabis Legalization

Twenty-three states1 and the District of Columbia (DC) have passed medical cannabis laws as of January 2015, and, of these, four states2 and DC have voted through ballot ini a ves to allow recrea onal use. Of the 23 states, 17 states3 and DC have adopted policies or rules governing pes cide use in cannabis produc on. A review of state laws reveals a mix of approaches in the absence of federal oversight. Six states,4 generally those without medical marijuana dispensaries (where medical marijuana is sold and o en grown in greenhouses), but including California (which has legalized medical marijuana and comprises nearly 50% of cannabis sales5 na onally), are silent on pes cide use in cannabis produc on, while ve6 oth- ers speci cally outlaw any applica on of a federally registered pes- cide. Of these, three states7 have adopted a speci c requirement that cannabis is grown without any pes cides.8 As with all crop pro- duc on systems, cannabis grown without toxic pes cides not only protects the consumer from pes cide exposure, but also the work- ers who grow the crop, and the environment where it is grown.

Pesticide Residues in Cannabis

Pes cide residues in cannabis that has been dried and is inhaled have a direct pathway into the bloodstream.9 Like other foodstu s, contami- nants consumed through foods mixed with cannabis may present an exposure hazard. It is logical to assume that the prohibi on on the use of a federally registered pes cide would result in a zero tolerance or allowable residue on the consumed cannabis. However, three states10 allow cannabis to contain pes cide residues of any federally registered pes cide up to a level less than the lowest legal residue of the pes cide on food. Oregon has set a generally acceptable level of .1ppm.11 This allowance of pes cide exposure does not account for the lack of EPA review of cumula ve risk or toxic body burden associated with the ad- di onal exposure to pes cide residues from cannabis.

Inhalation of Pesticide Residues

Very li le peer-reviewed research has been published on the health and safety risks associated with pes cides on dried cannabis. How- ever, the tests that have been performed show cause for signi cant consumer concern, par cularly medical pa ents or those with ele- vated risk factors.

Studies on tobacco provide good indica ons of the threats that may arise from smoking pes cide-laced products and, thus, the importance of state enforcement. A 2002 study, published in the Journal of Chromatography A, found that 1.5-15.5% of pyrethroid insec cides on treated tobacco is transferred to cigare e smoke.12 Signi cant levels of pes cide residues were found within the ciga- re e’s co on lter. In addi on to the transference of pes cide resi- due from the dried plant to the smoker, burning can cause pyrolysis (decomposi on) of the pes cide, forming toxic mixtures13 or other toxic pes cide contaminants.14 Addi onally, unlike most packaged tobacco products, cannabis is not typically ltered when its smoke is inhaled, and therefore smokers may expose themselves to much higher levels of pes cides and degradates.

A 2013 study, published in the Journal of Toxicology, found that up to 69.5% of pes cide residues can remain in smoked marijuana.15 Filtering the smoke through water showed only a slight reduc on in pes cide residues.16 However, when ltered through co on, pes- cide levels were similar to levels in tobacco, with 1-11% of tested pes cides reaching the user. Authors of the Journal of Toxicology study note that, “High pes cide exposure through cannabis smok- ing is a signi cant possibility, which may lead to further health com- plica ons in cannabis users.” The signi cance of these results may confound studies that have associated cannabis use with nega ve health outcomes, according to researchers.17

Cannabis Legalization and Pesticide Regulations in the U.S


Breakdown of Pesticide Product Categories

Federally Registered Pes cides: Unless determined to be minimum risk and exempt from registra on, pes cides, (including herbicides, insec – cides, roden cides, an microbial products, and biopes cides) must under- go EPA’s formal registra on process, which includes a scien c assessment of the ac ve ingredient that is included in pes cide products.

Organic pes cides: Pes cides allowed for use in organic produc on must be evaluated by the Na onal Organic Standards Board for their essen ality, impacts to human and environment health, and compa bility with organic prac ces. In general, natural pes cides are allowed unless speci cally prohibited and syn- the c pes cides are prohibited unless speci cally recommended by the NOSB.

List 25(b) – Federally Exempt Minimum Risk Pes cides: Minimum risk pes cides under sec on 25(b) of FIFRA are not required to undergo the federal registra on process if their ingredients are “demonstrably safe for its intended use.”21 Some states require state-level registra on of 25(b) pes cides, but do not conduct safety tes ng.

Pes cides Exempt from a Tolerance: EPA determines certain pes cides are exempt from a tolerance on a food crop based on toxicity and exposure data speci c to the pes cides’ use pa ern. Not all 25(b) pes cides are exempt from a tolerance.

Federal Pesticide Law

Pes cide use in the U.S. is governed by the Federal In- sec cide Fungicide and Roden cide Act (FIFRA), which establishes a goal of preven ng “unreasonable adverse e ects”18 from pes cide use. The law, passed in 1947 and overhauled in 1972, sets minimum use restric ons regarding the registra on and labeling of pes cides. FIFRA is implemented in coordina on with the Federal Food Drug and Cosme c Act, which establishes toler- ance limits for allowable pes cide residues on speci c crops, unless the agency determines the pes cide is exempt from a tolerance limit. Pes cides considered minimum risk under FIFRA’s sec on 25(b) criteria are exempt from federal registra on. Examples of mini- mum risk pes cides include lauryl sulfate, white pep- per, and certain essen al oils such as castor oil, euge- nol, cinnamon oil, and soybean oil. (See box, right, on 25(b) pes cides.)

(or exemp ng from) tolerance limits for pes cide residues on can- nabis crops, and given the plant’s classi ca on as a narco c, the evalua on of pes cide use, assessment of exposure hazards, and the se ng of pes cide use restric ons by EPA is also prohibited at the federal level.

The California Response –Medical Cannabis Use

California exempli es a state with a cannabis le- galiza on law at odds with U.S. narco cs law. Vot- ers in the state in 1996 passed the rst medical marijuana law in the country, the Compassionate Use Act, Prop 215. The measure allows pa ents to grow their own cannabis and assigns the regula- on of cul va on facili es to county agencies. Because California state law and regula ons are silent on the use of pes cides on cannabis, and given that there are no pes cides registered by EPA for use on the plant, use of federally registered pes cides in cannabis cul va on is not compliant with the law.

The California regulatory response to Prop 215 raises policy gaps speci c to cannabis as both an agricultural crop and a medical drug. A 2012 re- port commissioned by California Assembly mem- ber Linda Halderman, M.D., and produced by the nonpar san California Research Bureau, inves – gated the policy gaps in medical cannabis. The report raised more ques ons than it answered. To address regulatory uncertainty, it was deter- mined cri cally important that medical marijuana be legally de ned.

However, as it stands, there is no clear determina on as to whether medicinal cannabis is an agricultural crop or a medical drug.22 In the medical context, cannabis as a medicine is nevertheless derived from a crop, and the cul va on of the crop is subject to produc on input use restric ons. The report nds that because there are no pes cide products registered for use on cannabis by EPA under FIFRA, and given that applying a pes cide for an unregistered use is illegal under pes cide law, “[California Department of Pes cide Regula on] CDPR could con scate all medical marijuana crops treated illegally with pes- cides. . .” However, the report also notes that con sca on would violate the Compassionate Use Act, which guarantees ill Californians access to medical marijuana. California’s report notes that growers can simply not spray pes cides23 in order to avoid poten al con sca- on of their crops. However, Anthony Silvaggio, Ph.D., Professor at California State University Humbolt, states in the report, “There are very, very, very few 100% organic growers.”

The Washington State Approach
–Legalization of Recreational Cannabis Use
With the passage of laws legalizing recrea onal use of cannabis in the states of Washington and Colorado in 2012 and Alaska, Or- egon, and DC in 2014, there is a growing ques on of pes cide use in cannabis cul va on. States have begun to look to EPA for guid- ance and legal authori es.

Washington state took the proac ve step of reques ng guidance from EPA, according to a September 2014 document released by the Washington State Department of Agriculture (WSDA),24 the pes cide lead agency in the state. The state received the follow- ing response from EPA:

“In determining which pes cides, if any, might be used legally on marijuana, the WSDA asked the EPA if marijuana might t into any general crop groups, such as herbs, spices or vegetable gar- dens. EPA’s current posi on is that marijuana is not an herb, a spice or a vegetable. EPA considers marijuana to be a controlled substance, and has indicated that marijuana is not listed as a crop/site on any pes cide label. However, EPA does concede that, depending on actual label language, pes- cides may be legally used on marijuana under certain other very general types of crops/sites when there is an exemp on from the re- quirement of a tolerance.”

While WSDA had indicated that its regula on of pescides in cannabis cul va on “may be rescinded or superseded at any me,” the state is allowing pes cides (i) registered by EPA and the state,25 (ii) with ac ve ingredients exempt from tolerances, and (iii) with direc ons for use on “unspeci ed food crops, home gardens, or herbs.”26 Regarding 25(b) pes cides exempt from reg- istra on, WSDA indicates that the product must be registered with the state, and must also be labeled for use on “unspeci ed food crops, home gardens, or herbs” in order to be applied to can- nabis plants. However, WSDA does not speci cally acknowledge that not all 25(b) pes cides are exempt from tolerances on food crops. Further, WSDA explains that it nds pes cide use, including broad spectrum herbicides and soil fumigants, to be acceptable prior to plan ng marijuana outdoors as long as the label on the pes cide product does not specify the food crop to be planted a er the pes cide applica on.

Other states are inves ga ng standards similar to those adopted by WSDA. Colorado has proposed new rules that call for the develop- ment of an approved pes cide list.27 In the state of Nevada, regula- tors have convened an Independent Laboratory Advisory Commit- tee to establish a list of approved pes cides. As part of Illinois’ 2013 Medical Cannabis Pilot Program Act, the state’s regula ons include a list of allowed ac ve ingredients, rather than a list of products. However, Illinois rules do not allow synthe c ac ve ingredients, and disallows the applica on of pes cides to cannabis crops a er its vegeta ve stage.28

Pesticides that May Be Used and Health Effects

The use of pes cides not speci cally registered for use on a crop raises health and safety issues. An allowance of a pes cide use and exposure pa ern not evaluated for its poten al health im- pacts remains a concern among health advocates.

WSDA has compiled a list of 271 allowed pes cide products that t the criteria it developed in its opinion on cannabis produc on.29 A review of the list nds pes cides exempt from tolerances by EPA, such as py- rethrins, sulfur, and essen al oils. However, it appears that WSDA does allow a 25(b) material (sodium lauryl sulfate) that is not exempt from a tolerance.30 On the other hand, the synthe c piperonyl butoxide (PBO), frequently used as a synergist to enhance the toxicity of a pes cide product’s ac ve ingredient, is allowed by WSDA because its use in crop

produc on is exempt from a tol- erance.31 (See box at le on envi- ronmental e ects of pes cides.) PBO has been linked to numerous adverse human health impacts, including cancer, neurotoxic- ity, and adverse impacts on liver func on.32 Further, while natural pes cides are usually preferable to synthe c counterparts, prod- ucts containing pyrethrins and metals present an exposure risk to workers and wildlife.

Environmental Effects of Pesticides

Analysis of the environmental e ects of pes cides is
a part of the federal registra on process, and is based upon where a pes cide is used and its rate of applica on. Given the volume of pes cides used in the cul va on of cannabis, and its poten al to be grown both indoors and outdoors, the lack of an environmental assessment of pes cides exempt from tolerance raises ques ons about poten al e ects to nontarget plants and wildlife, as well as the en re ecosystem in which they are used.

Of concern is the use of broad spectrum synthe c herbicides and soil fumigants prior to the plan ng of cannabis. Although regula- tors in those states that allow herbicide use in cannabis cul va on may not consider this a human health issue because the chemicals are not being applied directly to consumable cannabis, chemicals in the soil can be taken up by the plants, and herbicide use can re- sult in water contamina on, wildlife e ects, and injury to workers.

Testing and Labeling for Production Practices

States have taken a wide variety of approaches to the tes ng and labeling of cannabis for pes cide residue and other contaminants. Twelve states34 require regulators to test random samples of can- nabis batches, a quan ty of cannabis produced at one me, for pes cide residues. New Mexico and Vermont require tes ng only a er a complaint of contaminants has been received. The District of Columbia requires growers to create a plan to test and ensure pa ents that cannabis is free of contaminants. Delaware requires dispensaries to develop a protocol for tes ng cannabis, but does not explicitly state that pes cides must be included. While rules for recrea onal cannabis in Colorado do not mandate laboratory analysis, if tes ng is not conducted, cannabis products must dis- play a label statement that reads, “The marijuana contained with- in this package has not been tested for contaminants.”

Four states35 and DC require both residue tes ng and the label- ing of all chemical pes cides used in the produc on of cannabis. Connec cut and Illinois require labels to indicate only whether the cannabis batch passed or failed

eral registra on. A er the cita on, Wellness Connec on and other medical cannabis providers in the state successfully lobbied for a bill, LD 1531, An Act to Maintain Access to Safe Medical Marijuana, that allows the applica on of 25(b) pes cides in the produc on of cannabis. Subsequently, Becky DeKeuster, Wellness Connec on ex- ecu ve director, told the Portland Press Herald that the company is now using environmental and mechanical methods, including ben- e cial predaceous insects, such as parasi c wasps, to control pests, and that it has no need to use even the 25(b) pes cides. “It’s good to have the 25(b)’s in the toolkit,” Ms. DeKeuster said to the Press Herald. She con nued, “Are they one of the rst things we’ll use? No, they’re probably one of the last.”

A Systems Approach to Cannabis Cultivation

Five states37 and DC are currently regula ng medical cannabis with some focus on ensuring proper growing prac ces that avoid or pro- hibit the use of pes cides as a priority. The state of Connec cut banned the use of all pes cides except in cases where infesta on would result in catastrophic loss (which is not de ned). And, be- fore this applica on can occur, producers must obtain authoriza on from state regulators. This strategy puts a focus on pest preven on, yet provides a backstop in the event of an emergency. However, Connec cut’s law does not require growers to have a produc on or pest management plan in place. Regulators have discre onary authority to allow pes cide exemp ons for producers. Moreover, the state does not detail what chemicals may be allowed to be used in the event of an emergency, raising the ques on of illegal use of a

laboratory tests. Oregon does not require an indica on of pass or fail, but does require the label to indi- cate the laboratory that performed the analysis. Delaware and Massa- chuse s require labels to include an indica on that the cannabis is free of contaminants, while New Hampshire, which mandates test- ing, also requires a label to note that the product is not cer ed to be free of contaminants.

The Maine Experience

In early 2013, Wellness Connec on, a medical marijuana dispensary with several loca ons throughout the state of Maine, was ned $18,000 by the Maine Department of Health and Human Services (MDHHS) for illegal pes cide applica ons. A p from an employee led to an inves- ga on.36 At the me, Maine’s law prohibited the use of any pes cides in cannabis produc on, both feder- ally registered and exempt from fed-

Maine and DC, which prohibit cul va- on centers from using synthe c pes- cides, require producers to be able to demonstrate knowledge of organic growing methods. New Mexico has a similar requirement on organic prac- ces, but new rules may strike this provision, weakening safety standards.

Minnesota regulators have adopt- ed rules that require producers to design the cul va on process in a way that limits contamina on. Although this language is broad, it shows a focus on a systems ap- proach to pest management. Mas- sachuse s and New Hampshire have similar language within their regula ons, but go further in pro- tec ng pa ent health. These two New England states are the only ones that require growers to fol- low cul va on prac ces consistent with organic methods.

In fact, seven states39 and DC cite organic produc on in their regu- la ons. Most include the subject only to note that cannabis can- not be labeled organic unless cer ed by the U.S. Department of Agriculture (USDA). As with EPA, given cannabis’ status as an il- legal narco c, USDA is barred from applying the organic seal to any end-use marijuana consumer product. However, in theory, independent cer ers could use their own seals to iden fy com- pliance with their standards. Despite this absence of the USDA cer ed organic seal and mandated organic produc on prac ces,

regula ons in Maine require dispensaries to indicate whether the cannabis sold meets organic standards. Under USDA organic regula ons, growers are required to create and follow an organic system plan (OSP) for their produc on process. The OSP must in- clude: a detailed descrip on of the prac ces and procedures that will be undertaken by the cer er producer, a list of substances to be used as a produc on input, a descrip on of how prac ces will be monitored, and recordkeeping requirements to ensure the plan is followed. Growers following organic standards must imple- ment cultural, mechanical, physical, or biological controls before considering the use of an allowed pes cide. Moreover, condi ons governing the use of any such pes cide must be included within the grower’s OSP.

Survey Findings Summary

Beyond Pes cides’ survey evaluates the pes cide use policies on cannabis produc on in 23 states and DC that have passed medical cannabis laws as of January 2015, including the four states and DC that have voted through ballot ini a ves to allow recrea onal use of marijuana. The survey ndings iden fy state ac ons regarding general pes cide restric ons, tes ng for pes cide contaminants, labeling of pes cide products applied to cannabis, and whether organic prac ces are addressed by regula ons.40 (See chart on page 22 for a summary.)

Allowed and Prohibited • Pesticides by State:

System Focus: Five states and DC are currently regula ng medical cannabis by focusing on requiring growing prac- ces that prevent the use of pes cides. Catastrophic Loss: Connec cut allows pes cide use only when authorized by a regulator to address catastrophic loss. Organic Knowledge: Two states and DC require a dispensary applicant’s knowl- edge of organic prac ces.

Organic Prac ces: Two states require growers to follow organic prac ces.

• No Pes cides: Three states have ad- Pesticide Testing:
opted regula ons that prohibit pes – Fourteen states address the tes ng of can- cide use in cannabis produc on. How- nabis plants for pes cide residue.
ever, discussions with state regulators •
indicate confusion on the allowance
of 25(b) pes cides. (See endnote 8.)

• Pes cide Use Lists: Washington state • maintains a list of allowed pes cide products, and three states are inves- ga ng the use of similar lists. •

Required: Twelve states require regu- lators to test random samples of can- nabis batches for pes cide residue. A er a Complaint: Two states require tes ng only a er a complaint about contaminants has been received. Uncertain: In one state and DC, the Analysis/Recommendations The survey results raise serious ques ons about pes cide expo- sure, inadequate regulatory oversight, and incen ves or require- ments to adopt sustainable prac ces in the cul va on of cannabis. While most state regula ons currently o er some level of protec- on for pa ents and consumers, it is important that this grow- ing $1.5 billion industry,42 authorized by numerous state laws, has clearer standards that restrict pes cide use and establish required sustainable cul va on systems based on the organic model. The restric ons should speci cally prohibit pes cides registered by EPA, but allow those exempt 25(b) pes cides.

Allowed and Prohibited Pes cides: In the absence of adequate tes ng at the federal level on the poten al impacts of pes cide use on cannabis to consumers, workers, and the environment, states should provide clear rules to producers regarding sustain- able produc on prac ces that protect public health and the en- vironment. Beyond Pes cides recommends that states follow an approach similar to New Hampshire, which restricts growers to pes cides that are (i) allowed for use in organic produc on and (ii) exempt from federal registra on (25(b)). It is cri cal that these re- stric ons also require a system plan that governs the poten al use of a pes cide a er alterna ve

ly allowed under state law, all states should require the labeling of all pes cides that have been applied to a cannabis plant throughout its en re produc on and processing.

Environmental Protec on: Exemp on from tolerance should not alone allow the use of a registered pes cide. Use pa erns (in ad- di on to those federally registered) could cause environmental damage that has not been evaluated. These include impacts on waterways and wildlife (including endangered species).

Organic Prac ces: States should pass laws or implement rules that require a systems approach to cannabis produc on. State re- quirements that growers follow na onal organic standards (with only exempt pes cides permi ed in organic) represent a posi ve trajectory for the industry.

EPA Guidance: Current EPA guidance is misleading and suggests al- lowances of pes cide use that can be damaging to public health and the environment due to a lack of federal assessment of pes cide use and exposure pa erns. EPA should simply no fy the states that pes – cides registered by the agency that are applied to elds or greenhous- es before plan ng, or on plants during cul va on or post-harvest are

means have been exhausted.

Pes cide Tes ng: State regula- ons should be wri en to in- clude the batch tes ng of pes- cide contaminants in cannabis sold. Tes ng laboratories should be independently cer ed, and the laboratory name should be disclosed on the product label. Relying on a complaint to inves- gate a supplier is not an e ec- ve means of enforcing safety standards, and unfairly places the burden on consumers and pa ents, who are likely to sub- mit a complaint only a er suf- fering injury or harm.


Pes cide use in the legal cul va- on of cannabis in 23 states raises serious concerns about protec on of public health and the environ- ment. Those states that have ad- opted a rma ve policies govern- ing cannabis cul va on vary in their clarity in restric ng pes cide use. EPA’s guidance has muddied the waters on this by sugges ng the allowance of pre-plan ng pes- cides and those with exemp on from tolerances, or used under generalized labels that allow use on unspeci ed crops. Most im- portantly, six states of the total that have legalized cannabis pro- duc on are silent on the issue of pes cide use, which raises serious ques ons about their e orts to

A quarterly publication of Beyond Pesticides

Vol. 34, No. 4 Winter 2014-15

enforce against the use of pes cides. The public and environment require uniform protec ons that include the following three basic elements:

  1. Prohibi on of federally registered pes cide use.
  2. Allowance of pes cide exempt from federal registra on, but not those that are only exempt from tolerances.

3. Requirements for an organic system plan that focuses on sus-

tainable prac ces and only 25(b) products as a last resort.

Ma hew Porter contributed to this piece.


  1. AK, AZ, CA, CO, CT, DE, HI, IL, ME, MD, MA, MI, MN, MO, NV, NH, NJ, NM, NY, OR, RI, VT, and WA.
  2. AK, CO, OR, and WA.
  3. AZ, CO, CT, DE, IL, ME, MA, MN, NV, NH, NJ, NM, OR, VT, and WA states.
  4. AK, CA, HI, MI, MO, and RI.
  5. Ferner, Ma . 2015. Hu ngton Post. Legal Marijuana is the Fastest-Growing Industry in the U.S.: Report. h p://www.hu ngtonpost.


  6. DE, MA, NH, NJ, and VT.
  7. DE, NJ, and VT. Personal communica on with state regulators suggeststhat the laws ci ng “pes cide” prohibi on are referring to “federally registered” pes cides and may allow pes cides exempt from federal registra on, known as FIFRA 25(b) pes cides.
  8. Delaware: Title 16 Health and Safety, 4470 State of Delaware Medical Marijuana Code, 7.1.4 “Use of pes cides is prohibited: There are no pes cides authorized for use on marijuana; as such, a compassion center shall not apply pes cides in the cul va on of marijuana.”New Jersey: Adopted New Rules NJAC 8:64 -10.9 Pes cide Use Prohib- ited “Inasmuch as there are no pes cides authorized for use on marijua- na, and the unauthorized applica on of pes cides is unlawful, an ATC shall not apply pes cides in the cul va on of marijuana.”

    Vermont: Rules Governing the Vermont Marijuana Program, Sec on 6 “No pes cide use. There are no pes cides authorized for use on mari- juana, and unauthorized applica on of pes cides is unlawful.”

  9. Ogg, Clyde L. et al. 2012. Managing the Risks of Pes cide Poisoning and Understanding the Signs and Symptoms. University of Nebraska Exten- sion. h p://ianrpubs.unl.edu/live/ec2505/build/ec2505.pdf.
  10. CT, IL, NV.
  11. Oregon: “A sample of usable marijuana shall be deemed to test posi vefor pes cides with a detec on of more than 0.1 parts per million of any

    pes cide.”

  12. Cai, Jibao et al. 2002. Determina on of pyrethroid residues in tobaccoand cigare e smoke by capillary gas chromatography. DOI: 10.1016/


  13. Lorenz, W. et al. 1987. Thermolysis of Pes cide Residues During TobaccoSmoking. Chemosphere. Vol.16, Nos.2/3, pp 521-522, 198.
  14. Rodgman, Alan and Perfe , Thomas. 2013. The Chemical Componentsof Tobacco and Tobacco Smoke, Second Edi on. Page 1105, Table 21.2

    Degrada on Products of Pes cides in MSS.

  15. Sulivan, Nicholas et al. 2013. Determina on of Pes cide Residues inCannabis Smoke. Journal of Toxicology. Volume 2013 (2013), Ar cle ID

    378168, 6 pages h p://www.hindawi.com/journals/jt/2013/378168/.

  16. Ibid.
  17. Ibid.
  18. For more of Beyond Pes cides take on risk assessment in FIFRA, seeKepner, John and Feldman, Jay. 2006. Taking o the Blindfold, EPA ignores

    toxic exposures in risk assessment. Pes cides and You. Beyond Pes cides.

  19. See Wisconsin Public Intervenor, et al., Pe oners v. Ralph Mor er et al.501 U.S. 597 (1991).
  20. See Porter, Ma . 2014. State Preemp on Law. Pes cides and You.Beyond Pes cides.
  21. Environmental Protec on Agency. 2014. Minimum Risk Pes cides.h p://www.epa.gov/pes cides/biopes cides/regtools/25b_list.htm.
  22. Lindsey, Tonya D. 2012. Medical Marijuana Cul va on and Policy Gaps. California Research Bureau. h p://www.canorml.org/prop/CRB_Pes -cides_on_Medical_Marijuana_Report.pdf.
  23. It appears that the reference to “pes cides” in California is to federallyregistered pes cides and not not those exempt from federal registra on

    (25(b) pes cides) and not registered by the state of California.

  24. Washington State Department of Agriculture. 2014. Criteria for Pes cidesUsed for the Produc on of Marijuana in Washington. h p://agr.wa.gov/

    FP/Pubs/docs/398-WSDACriteriaForPes cideUseOnMarijuana.pdf.

  25. State registra on, with the excep on of California, is simply a licensingprocess and does not impose independent toxicological or environmen-

tal assessments as a rou ne.
26. EPA and WSDA registra on is required: (i) Prior to distribu on of the

pes cide; (ii) Prior to plan ng marijuana outdoors (such as a eld), use
of a pes cide (e.g.,broad spectrum herbicide, soil fumigant) is allowed if the food crop to be planted following applica on is not speci ed on the label; (iii) Prior to plan ng marijuana in an enclosed facility (such as a greenhouse), use of a pes cide (e.g., disinfectant, sani zer) is allowed to control microorganisms on surfaces (such as benches, oors, pallets, pots, skids).
Use of a pes cide on marijuana is allowed if: (i) The ac ve ingredient is exempt from the requirements of a tolerance (e.g., auxins, biopes cides [most ac ve ingredients], copper, cytokinins, gibberellins, petroleum oil, phosphorous acid, pyrethrins, soap, sulfur), and (ii) The label has direc ons for use on unspeci ed food crops, home gardens or herbs (outdoor or enclosed), including unspeci ed food crops or herbs grown as bedding plants. (Marijuana will not be speci cally listed as a crop on the pes cide label.)
Sec on 25b minimum risk pes cides (exempt from federal registra- on): (i) WSDA registra on is required prior to distribu on of the pes cide; (ii) Use on marijuana is allowed if the product is labeled for use on unspeci ed food crops,home gardens or herbs (outdoor or enclosed), including unspeci ed food crops or herbs grown as bedding plants. (Marijuana will not be speci cally listed as a crop on the pes – cide label.)

27. Colorado Department of Agriculture Plant Industry Division. 2014. Proposed Rule: Criteria for Determining the Legal Use of Pes cides in Marijuana Cul va on. 8 CCR 1203-25.

28. The consumable product of the cannabis plant is the ower, which is produced a er the vegeta ve stage. Barring pes cide applica ons a er the vegeta ve stage prevents pes cide applica ons from being made directly to the end-use product.

29. Washington State University Pes cide Informa on Center Online. 2014. WA I502 list. h p://cru66.cahe.wsu.edu/labels/Labels.php?SrchType=.

30. The product in ques on is Messina Wildlife’s Mole and Vole Stopper. h p://cru66.cahe.wsu.edu/~picol/pdf/WA/54761.pdf.

31. h p://www.gpo.gov/fdsys/pkg/CFR-2008- tle40-vol23/xml/CFR- 2008- tle40-vol23-sec180-905.xml.

32. Beyond Pes cides. 2006. ChemicalWATCH Factsheet – Piperonyl Butox- ide. h p://www.beyondpes cides.org/pes cides/factsheets/Pipero- nyl%20Butoxide.pdf.

33. Environmental Protec on Agency. 2014. Pes cides: Environmental E ects. Ecological Risk Assessments. h p://www.epa.gov/pes cides/ ecosystem/ecorisk.htm.

34. AZ, CO (medical), CT, IL, ME, MA, MN, NV, NH, NJ, OR, and WA. 35. AZ, CO (medical), NV, and WA.
36. Ricker, Nok-Noi. 2013. Maine marijuana growing center cited for

using pes cides. Bangor Daily News. h p://bangordailynews. com/2013/03/25/news/state/maine-marijuana-cul va on-center-used- pes cides-state-o cial-says/.

37. CT, MA, ME, NH, and NM.
38. Since federally registered pes cides may be used in organic agriculture,

their use in cannabis produc on (a non-labeled used) should be consid- ered an illegal applica on, except that EPA allows some pes cides to be used on “unspeci ed crops.”

39. CT, ME, MA, NV, NH, NJ, and WA.
40. Note that most states address pes cide use on cannabis through rules

or regula ons, which are subject to change. This analysis does not address other cannabis related issues such as user access, caretakers, ability to grow your own, licensing fees, or taxes.

41. Statement must read: “The marijuana product contained within this package has not been tested for contaminants.”

42. Karnes, Ma hew. 2014. State of the Emerging Marijuana Industry Current Trends and Projec ons. GreenWave Advisors. h ps://www.gre- enwaveadvisors.com/wp-content/uploads/GreenWave_Report_ES.pdf.

Vol. 34, No. 4 Winter 2014-15 Pesticides and You
A quarterly publication of Beyond Pesticides

Pesticides and You Vol. 34, No. 4 Winter 2014-15 A quarterly publication of Beyond Pesticides

Pesticide Laws in States with Legalized Cannabis (Marijuana) Production


Pes cide Restric ons

Pes cide/Contaminant Tes ng

Pes cide Labeling

Organic Discussed

State Act or Regula on

Alaska –Medical

To be determined. No

To be determined.
Tes ng for pes cide residues required.

To be determined.

To be determined. No

Alaska Statutes, Chapter 37: Medical Uses of Marijuana Program.

–Recrea onal Arizona

“An Act to Tax and Regulate the Pro- duc on, Sale, and Use of Marijuana.”





SB 420, Lindsey, Tonya D. 2012. Med- ical Marijuana Cul va on and Policy Gaps. California Research Bureau.

Colorado –Medical

Individual locali es may further regulate.

Tes ng for pes cide residues required.

Yes –list of all chemical addi ves used in produc on.

No No

Colorado Department of Revenue. 1 CCR212-1.

–Recrea onal


Not required, but, if not performed, must state on label, “The marijuana contained within this package has not been tested for contaminants.”

Yes –list of all non-organic pes – cides used in produc on.

Colorado Department of Revenue. 1 CCR212-2.

Connec cut

Pes cide use not allowed unless autho- rized by regulator to address infesta on that would result in catastrophic loss.

Tes ng for pes cide residues required; those that exceed acceptable levels (higher than most stringent residue standard on any food as set by EPA) must be disposed.

Must list whether the product passed/failed laboratory tests.

Not allowed to be labeled organic unless cer ed to be consistent with na onal organic standards.

State of Connec cut. Department of Consumer Protec on Regula ons. Sec. 21a-408.


Use of pes cides prohibited.

Dispensaries required to develop tes ng protocol, which may or may not include pes cide contaminants.

Dispensaries required to develop labeling that includes details indica ng the medical marijuana is free of contaminants.


4470 State of Delaware Medical Marijuana Code.

District of Columbia –Medical

Cul va on centers forbidden from using synthe c pes cides.

Dispensaries required to describe plan
for tes ng or verifying medical marijuana received from a cul va on center and ensuring that all medical marijuana is free of contaminants.

Yes –list of all chemical addi ves used in produc on.

Cul va on center applicants must demonstrate knowledge of organic growing methods.

District of Columbia Title 22-C.

–Recrea onal Hawaii

To be determined. No

To be determined. No

To be determined. No

To be determined. No

DC Ini a ve 71


Department created a list of approved pes cide ac ve ingredients; pes cides may not be applied a er the vegeta ve stage of a cannabis plant.

Tes ng for pes cide residues required –product deemed to pass if lower than most stringent acceptable standard for the pes cide residue on any food item, as set by EPA; publish list of labs that can test medical cannabis.

Must list whether the product passed/failed laboratory tests, producer must have plan for ensuring cannabis is free of contaminants.


Illinois Department of Agriculture. 8 Ill. Adm. Code 1000.


Only pes cides exempt from a federal registra on allowed.

Tes ng for pes cide residues required.


Require producer knowledge of organic prac ces; not allowed to be labeled organic unless cer ed to be consistent with na onal organic standards; must provide pa ents informa- on whether products meet organic cer ca on standards.

Rules Governing the Maine Medical Use of Marijuana Program. 10- 144CMR Chapter 122.

Yes –list of all chemical addi ves used in produc on.

Title 9. Health Services. Chapter 17. Department of Health Services Medi- cal Marijuana Program.

Hawaii Administra ve Rules. Chapter 23-202

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Algal Blooms are the result of man made pollution of organic nitrogen

Submitted as a Public Service by the editors and moderators of APP Advocate Precautionary Principle

For more information visit the APP Blog https://appprecautionaryprinciple.wordpress.com/about/
To combat the algal blooms near shore in Florida we must first admit the scientific proven fact. The fact is that algal blooms are the result of land based activities (man made pollution of organic nitrogen) from sewage spills septic tanks leaks and and overuse of organic nitrogen from manure on lawns.  All of this we can abate if we have the will. (more…)

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It’s been said that weeds are just plants whose virtues have not yet been discovered. True plant vegetable gardens and pull up that lawn,
But if you’re tired of waiting to find out what those virtues are, you might want to use one of these homemade herbicides instead of the chemical versions.
Many common weeds can be either food, medicine, or unwanted visitors to the garden, depending on the varieties and how you view them. But if you’ve eaten all of them you can, and you still need to get rid of weeds in your yard, it’s far better for you, your soil, and your local waterways to choose a more environmentally friendly herbicide than those commonly found in the home and garden center.
Strong chemical herbicides, pesticides, and fungicides can end up polluting our drinking water, our groundwater, and surface water, so it’s important to consider the longer term effects of using them, and to instead make the choice to use a gentler herbicide, which won’t contribute to the larger issue of water contamination. (more…)

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