Petition to List Commercial Cannabis and Hemp Cultivation Operations under Clean Air Act and Petition to List β-Myrcene as a Hazardous Air Pollutant under the CAA

January 10, 2026

By email

Administrator Lee Zeldin (Zeldin.Lee@epa.gov)

U.S. Environmental Protection Agency

1200 Pennsylvania Avenue, N.W.

Washington, D.C. 20460

Re: Petition to List Commercial Cannabis and Hemp Cultivation Operations under § 111(B)(1)(A) of the Clean Air Act (CAA); to Promulgate Standards of Performance under §§ 111(B)(1)(B) and 111(D) of the CAA; and Petition to List β-Myrcene as a Hazardous Air Pollutant under § 112 of the CAA

Dear Administrator Zeldin:

With the enclosed petitions, the Neighborhood Coalition hereby asks the U.S. Environmental Protection Agency to List Commercial Cannabis and Hemp Cultivation Operations under § 111(B)(1)(A) of the Clean Air Act (CAA); to Promulgate Standards of Performance under §§ 111(B)(1)(B) and 111(D) of the CAA; and Petition to List β-Myrcene as a Hazardous Air Pollutant under § 112 of the CAA.

We look forward to your attention and response to these petitions.

Sincerely yours,

Dr. Deborah Eppstein

Craig S. Harrison

cc: Aaron Szabo, Assistant Administrator for Air and Radiation (Szabo.Aaron@epa.gov)

David Fotouhi, Deputy Administrator (Fotouhi.David@epa.gov)

Peter Tsirigotis, Director, Office of Clean Air Programs (tsirigotis.peter@epa.gov)

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BEFORE THE UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

THE NEIGHBORHOOD COALITION, Petitioner.

v.

LEE ZELDIN, ADMINISTRATOR, U. S. ENVIRONMENTAL PROTECTION AGENCY, Respondent.

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PETITION TO LIST COMMERCIAL CANNABIS AND HEMP CULTIVATION OPERATIONS UNDER § 111(B)(1)(A) OF THE CLEAN AIR ACT; TO PROMULGATE STANDARDS OF PERFORMANCE UNDER § 111(B)(1)(B) AND § 111(D) OF THE

CLEAN AIR ACT; AND PETITION TO LIST β-MYRCENE AS A HAZARDOUS AIR POLLUTANT UNDER § 112 OF THE CLEAN AIR ACT

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I. INTRODUCTION.

The Neighborhood Coalition hereby petitions the U.S. Environmental Protection Agency (EPA) to use its authority under Clean Air Act (CAA or the Act), § 111, 42 U.S.C. § 7411, (1) to list commercial cannabis and hemp cultivation operations (CCOs) as a category of sources under CAA § 111(b)(1)(A); (2) to promulgate standards of performance for new CCOs under CAA § 111(b)(1)(B); and (3) to prescribe regulations for State performance standards for existing CCOs under CAA § 111(d). The Neighborhood Coalition hereby simultaneously petitions EPA to use its authority under CAA § 112, 42 U.S.C. § 7412, to add β-Myrcene, a primary terpene in cannabis and hemp emissions, to the Hazardous Air Pollutant list. Both petitions are supported by the identical factual basis.

During recent decades, cannabis (also called marijuana) has become legal in 40 states for medical use and 24 states for recreational use.1 The 2018 Farm bill legalized the cultivation of industrial hemp under federal law.2 Industrial hemp is the identical plant as marijuana (genus Cannibis), except hemp by federal law is limited to 0.3% THC (Delta-9-Tetrahydrocannabinol) content. As a result of these developments, increasing numbers of commercial CCOs are being operated throughout this nation because of opportunities for the sale of cannabis, cannabis products, hemp, and hemp products. Cannabis and hemp products include those containing cannabinoids and/or terpenes. Some describe this phenomenon as a “Green Rush.”

CCOs contribute significantly to anthropogenic emissions of terpenes, especially β-Myrcene, which is toxic and carcinogenic to humans and animals.3 The California Office of Environmental Health Hazard Assessment deemed β-Myrcene to be a carcinogen in 2015.4 In addition to toxicity and carcinogenicity, inhalation of noxious cannabis emissions from cannabis cultivation can nausea, headaches, cough, eye irritation, and respiratory distress including asthma.5 Despite these public health risks, EPA does not require CCOs to meet any testing, performance, or emission standards under the CAA. Given available evidence, much of it summarized in this petition, the EPA Administrator has reasonable cause to find, and should find immediately, that air emissions from CCOs cause and contribute significantly to air pollution that is reasonably anticipated to endanger public health and welfare. Because CCOs emit significant amounts of air pollutants which have been shown to have negative effects on human health and on welfare, the Administrator must promulgate nationwide standards of performance to minimize the impacts from new and existing CCOs and add β-Myrcene to the list of Hazardous Air Pollutants.

which is toxic and carcinogenic to humans and animals.3 The California Office of Environmental Health Hazard Assessment deemed β-Myrcene to be a carcinogen in 2015.4 In addition to toxicity and carcinogenicity, inhalation of noxious cannabis emissions from cannabis cultivation can nausea, headaches, cough, eye irritation, and respiratory distress including asthma.5 Despite these public health risks, EPA does not require CCOs to meet any testing, performance, or emission standards under the CAA. Given available evidence, much of it summarized in this petition, the EPA Administrator has reasonable cause to find, and should find immediately, that air emissions from CCOs cause and contribute significantly to air pollution that is reasonably anticipated to endanger public health and welfare. Because CCOs emit significant amounts of air pollutants which have been shown to have negative effects on human health and on welfare, the Administrator must promulgate nationwide standards of performance to minimize the impacts from new and existing CCOs and add β-Myrcene to the list of Hazardous Air Pollutants. a Hazardous Air Pollutant will create a strong incentive for new CCOs to use methods that protect public health and welfare. It will enable government agencies and private citizens to enforce the applicable standards when owners or operators of CCOs violate those emissions limits. In addition, EPA must act immediately to prescribe regulations for states to set performance standards for existing CCOs.

The threat to public health and welfare caused by the air pollutants emitted by CCOs necessitates an immediate determination that CCOs cause or contribute significantly to the air pollution that endangers public health and welfare, the listing of CCOs, their regulation by EPA under CAA § 111, and the addition of β-Myrcene to the list of Hazardous Air Pollutants. The Administrator should list CCOs under § 111(b)(1)(A) as an industry requiring regulations under CAA §§ 111(b)(1)(B) and (d), that reflect the “degree of emission limitation achievable through the best system of emissions reduction that has been adequately demonstrated.” 42 U.S.C. §§ 7411(a)(1), (b), (d).

Accordingly, for the reasons discussed below, as further detailed in the exhibits, the Neighborhood Coalition respectfully requests that EPA undertake rulemakings that:

• find that the emissions of terpenes from CCOs, including the toxin/carcinogen β-Myrcene, constitute air pollution that endangers U.S. public health or welfare;

• announce the Administrator’s judgment that emissions of terpenes, including the toxin/carcinogen β-Myrcene, from CCOs contribute significantly to air pollution that is reasonably anticipated to endanger public health and welfare;

• list CCOs as a category of stationary sources pursuant to CAA § 111(b);

• promulgate for CCOs performance standards for air emissions of terpenes, including the toxin/carcinogen β-Myrcene, from new and existing CCOs pursuant to the authority of CAA §§ 111(b) and 111(d); and

• add β-Myrcene to the list of Hazardous Air Pollutants pursuant to CAA § 112(b)(3)(B).

II. INTERESTS OF THE PETITIONER.

The Neighborhood Coalition is a non-profit charitable organization based in Sonoma County, California. It advocates for sustainable, environmentally sound, and neighborhood-compatible cannabis policies in conjunction with education of the public on the health and safety impacts of cannabis use. Many of the Neighborhood Coalition’s members have personal experience living near CCOs with the attendant health and welfare problems caused by unhealthy cannabis emissions. Its members are affected by the air pollution caused by CCOs. They have a strong personal interest in protecting their own health as well as the health of their families and neighbors. Dr. Deborah Eppstein, who holds a PhD in biochemistry,6 is the primary scientific advisor to the Neighborhood Coalition. The Neighborhood Coalition files this petition both on its own behalf and on behalf of its members.

III. LEGAL BACKGROUND.

A. The Clean Air Act.

The CAA is the primary federal statute regulating air quality and air pollution. The CAA was enacted “to protect and enhance the quality of the Nation’s air resources so as to promote the public health and welfare and the productive capacity of its population.” 42 U.S.C. § 7401(b)(1). EPA is the agency charged with implementing the Act’s mission and is the national leader for the federal air programs and the delegating authority to state programs.

1. CAA Section 111: New Source Performance Standards. In 1970, Congress amended the Act to include nationwide uniform emission standards for categories of stationary sources to complement national ambient air quality standards and prevent new pollution problems. 42 U.S.C. § 7411. Section 111 addresses air pollution problems that endanger public health and welfare, and are common to an industry. Section 111 performance standards apply regardless of a region’s ambient air quality and are triggered when a new source is constructed or an existing source undergoes a major modification. The Act requires the EPA Administrator to set and revise “a list of categories of stationary sources” that cause, or contribute significantly to, air pollution which may reasonably be anticipated to endanger public health or welfare. 42 U.S.C. § 7411(b)(1)(A). Section 111 further requires the Administrator to set standards of performance for new sources in a listed category within one year of listing, 42 U.S.C. § 7411(b)(1)(B), and to prescribe regulations for existing sources in a listed category, 42 U.S.C. § 7411(d). Performance standards under § 111 are to “reflect … the degree of emission limitation achievable through the application of the best system of emissions reductions which (taking into account the cost of achieving such reduction and any non-air quality health and environmental impact and energy requirements) the Administrator determines has been adequately demonstrated.” Lignite Energy Council v. U.S. E.P.A., 198 F.3d 930, 932 (C.A.D.C., 1999); 42 U.S.C. § 7411(a)(1). This technology requirement is called “best demonstrated technology.”

A stationary source is defined as “any building, structure, facility, or installation which emits or may emit an air pollutant.” 42 U.S.C. § 7411(a)(3). In determining what meets the standard for listing for a category of sources in § 111, the Act defines several terms to guide decision making. An “air pollutant” is broadly defined as “any air pollution agent or combination of such agents, including any physical, chemical, biological…substance or matter which is emitted into or otherwise enters the ambient air. Such term includes any precursors to the formation of any air pollutant…” 42 U.S.C. § 7602(g). To determine whether a particular air pollutant meets the endangerment standard required by § 111, the Administrator considers its effect on public health and welfare. While the CAA does not define “public health,” the legislative history defines the term broadly. See American Lung Ass'n v. E.P.A., 134 F.3d 388, 388 (D.C. Cir. 1998). The Act states that all “language referring to effects on welfare includes, but is not limited to, effects on soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility, and climate, damage to and deterioration of property, and hazards to transportation, as well as effects on economic values and on personal comfort and well-being, whether caused by transformation, conversion, or combination with other air pollutants.” 42 U.S.C. § 7602(h). This sweeping definition guides and supports the Administrator’s ability to list and regulate new and existing CCOs under CAA § 111 as shown below

2. CAA Section 112: Hazardous Air Pollutants.

In 1990, Congress amended the Act to require technology-based National Emission Standards for Hazardous Air Pollutants. 42 U.S.C. § 7412. The amended Act includes an initial list of 189 specific hazardous air pollutants to be regulated. 42 U.S.C. § 7412(b)(1). It provides that “any person may petition the Administrator to modify the list of hazardous air pollutants,” and “such petition shall include a showing by the petitioner that there is adequate data on the health or environmental defects of the pollutant or other evidence adequate to support the petition.” 42 U.S.C. § 7412(b)(3). “Within 18 months after receipt of a petition, the Administrator shall either grant or deny the petition by publishing a written explanation of the reasons for the Administrator’s decision.” Id. After a substance is added to the list of Hazardous Air Pollutants, the Administrator must promulgate applicable national emission standards for hazardous air pollutants pursuant to 42 U.S.C. § 7412(d).

IV. FACTUAL BACKGROUND.

There is no dispute that CCOs produce and emit gases into the ambient air from cannabis plants, both marijuana and hemp. Many of the gases emitted from CCOs have been incontrovertibly linked to health and environmental harms. Notable among the effects of these gases are risks to human respiratory health.

Cannabis plants emit many volatile organic compounds (VOCs), including 140 different terpenes.7 A terpene is a volatile, unsaturated hydrocarbon, and includes β-Myrcene and α- Linolenic acid; terpenes comprise a significant component of cannabis emissions. The characteristic “skunk” odor from cannabis plants is primarily due to volatile thiols, which tend to be created when α-Linolenic acid breaks down under ultraviolet rays of sunlight into methyl and butyl thiols.8 In recent years terpene content in cannabis has been increasing. Cannabis plants have been selectively bred for high-terpene content because consumers prefer terpene-rich products, and commercial producers prefer them because of their consequent command of higher wholesale prices.9 Commercial producers employing a combination of high-terpene-cultivars with various optimization and enhancement techniques can quintuple terpene content.10 The strong smell emitted from cannabis cultivation is noxious to most people. All people have “sensitive receptors” to cannabis terpenes, whether babies, children, adults, or the elderly. Children are generally at greater risk of respiratory harm; their lungs are still developing and they are more susceptive to air pollutants.11 People with conditions such as asthma or other respiratory diseases, or any illness whether acute or chronic, can be even more adversely affected. Residents living adjacent to cannabis cultivation sites who are exposed to noxious terpenes experience symptoms such as nausea, headaches, difficulty breathing, cough, eye irritation, and sore throat.12 Some people develop asthma exacerbations or even new-onset asthma.13 In Sonoma County, neighbors living adjacent to outdoor cultivation sites often cannot open windows or use their yards during the summer and fall due to the overpowering odor from CCOs.14 Some residents require gas masks to be able to use their yards, as depicted in the New York Times.15

Exposure to the stench of cannabis increases electric consumption and raises utility bills because natural air conditioning by opening windows at night, common in California during summer and autumn, is impossible. In Santa Barbara County wine tourism has been negatively impacted when cannabis emissions have encroached on vineyards and tasting rooms.16

The marijuana industry claims that cannabis emissions are just another agricultural odor like ammonia and hydrogen sulfide that waft from manure. Some say that rural residents should either accept breathing cannabis emissions in their homes or move elsewhere. Cannabis emissions are not a mere nuisance; they are dangerous to human health. In 2015, California’s Environmental Protection Agency’s Office of Environmental Health Hazard Assessment listed β- Myrcene as a chemical known to cause cancer.17 β-Myrcene can account for 50-70% of the volatile organic compounds in cannabis emissions. β-Myrcene is highly volatile and can travel 2 miles or more if downwind.18 In contrast, emissions from poultry and cow manure consist of hydrogen sulfide, methane, and carbon dioxide. None are deemed to be carcinogens.

A. CCOs.

Most CCOs are not “agriculture” in the conventional sense of the word. Former U.S. Attorney McGregor Scott in Sacramento described commercial CCOs as “industrial agriculture.”19 Various chemicals and additives are used, often lacking local soils. The activity intensely uses water and fertilizers. Plants are manipulated and processed. Female plants are not exposed to pollen because this would inhibit the production of THC, cannabidiol (CBD), and terpenes, as well as result in seeds in the buds, lowering the commercial value. California excludes marijuana from State “right to farm” protections against being sued for nuisances. It defines marijuana cannabis as an “agricultural product,” not an agricultural crop. Cal. Bus. and Prof. Code § 26067.

Outdoor cannabis plants in California are typically grown in “grow bags” or “geo pots” as depicted below, with highly amended soils, including chemical additives and soils that are often brought in from offsite. High humidity and dampness in many parts of coastal California facilitate molds that destroy cannabis plants. Accordingly, most “outdoor” grows are in hoop houses for much or all the growing season, as depicted below. Hoop houses are open to the ambient air. Even a one-acre outdoor CCO has a high level of activity that requires fifteen or more employees working daily, and larger operations have correspondingly more workers

Indoor CCOs are common in many regions of this nation such as Colorado because weather precludes outdoor cultivation much of the year. Even in benign climates in Southern California, indoor CCOs are common in locations such as Carpentaria. They typically employ HVAC systems and dehumidifiers to maintain consistent temperatures, air circulation, and proper moisture levels to avoid mold and rot, and consequent cannabis loss. A filtration system can control particles and odors in the growing area. Filters can prevent VOCs from encroaching nearby properties and subjecting neighbors to unhealthy cannabis emissions. Indoor commercial grow rooms rely on adjustable overhead grow lights. Notably, confirming the toxicity of the emissions from the plants, workers at indoor grows typically wear protective gear tantamount to “moon suits” to protect them from the plants’ toxic emissions. Marijuana grown under controlled indoor conditions is typically several times more aluable than cannabis grown outdoors.20

Because of health and other problems associated with outdoor CCOs, few people voluntarily live near one. A private survey of Sonoma County residents in 2018 found that 75% want to live at least 1/4 mile away; 62% want to be at least ½ mile away; and 52% at least one mile away. Only 19% were comfortable living adjacent to a CCO. These findings parallel the results of a poll taken by the Sonoma County Press Democrat.21

B. CCOs Emit Unhealthy and Hazardous Volatile Organic Compounds.

EPS defines VOCs as “any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions. . . .” 40 C.F.R. § 51.100(s). Outdoor CCOs produce large amounts of unhealthy and hazardous VOC emissions,22 especially terpenes such as β-Myrcene, that cause negative effects on people who work in a CCO.23 As noted above, in recent decades cannabis plants have been bred and manipulated to maximize terpene content.24 Neighbors living near outdoor CCOs are involuntarily exposed to unhealthy emissions containing β-Myrcene and other toxic substances. Large outdoor cannabis grows can blanket large areas with hazardous emissions and noxious odors that harm residents, food products, wine grapes, and tourism. Such problems occur in Santa Barbara County, California, where a certified class action nuisance suit against an outdoor CCO is scheduled for trial in 2026.25

Cannabis plants emit unhealthy and hazardous compounds especially during flowering and harvest.26 Exposures are amplified when winds blow cannabis emissions toward residences, especially in locations such as valleys where thermal inversions can trap them. Cannabis emissions can travel far even without wind. As depicted in the map below, marijuana emissions from a one-acre outdoor CCO in autumn 2023 in Bennett Valley, Sonoma County, was detected up to 8,000 feet from a CCO (red square; each concentric circle is 1,000 feet). Residents of a home 2,500 feet from the CCO could not open their windows or use their yards for several weeks. Neighbors can be exposed to the hazardous odors for months at a time, 24 hours a day, seven days per week. Depending on the proximity to neighboring properties, wind direction, topography, climatic conditions, meteorology, and stage of plant growth, appropriate separation distances from outdoor grows can require thousands of feet or even two miles from a CCO.27

C. Hazardous Emissions from Cannabis Plants.

β-Myrcene, a dominant terpene in most varietals of cannabis,28 is carcinogenic.29 The cumulative levels of β-Myrcene and other terpenes inhaled by people living near outdoor CCOs, as discussed below, can be at levels that are projected to be toxic if not carcinogenic.30 The risks are greater for children, the elderly, the infirm, and likely fetuses in utero. Cannabis emissions can cause immediate deleterious health effects such as nausea, headaches, cough, eye irritation, respiratory distress, and asthma.31 β-Myrcene was the sensitizing agent in a hops-caused respiratory hypersensitivity and impaired driving-related skills.32 β-Myrcene contributes to the formation of secondary pollutants, including formaldehyde and formic acid,33 both of which cause eye irritation and nausea.34 Formaldehyde, a carcinogen listed under California’s Proposition 65, reacts with air to form ground-level ozone,35 another known irritant.

1. Toxicity and Carcinogenicity Testing in Animals.

Toxicity testing in animals such as rodents is a normal first step before testing any new drug candidate in humans. The National Toxicology Program (NTP) tested β-Myrcene for carcinogenicity due to its use as a flavoring food additive (albeit in very small amounts) and its similarity to D-Limonene, another terpene that NTP had previously tested.36 The pharmaceutical industry and the Food and Drug Administration (FDA) understand that even a non-toxic dose in mice or rats may be toxic in humans, and clinical trials typically start at one-tenth of the nontoxic dose in animals. Compounds that are carcinogens in animal testing are often terminated from entering clinical trials for human pharmaceutical drug development. The NTP studies showed β-Myrcene caused kidney and liver toxicity in rodents after 70 days, and at two years caused cancer in mice and rats at the lowest dose tested by oral gavage.37 Toxicity increased with duration of dosing from three weeks to two years, including liver and kidney toxicities, chronic inflammation, bone marrow and lymph node atrophy, and tissue necrosis. At the highest dose tested, all rodents died within a week. At the two-year point, liver and kidney cancers developed at the lowest dose. These results prompted California in 2015 to list β-Myrcene under Proposition 65 as a compound known to cause cancer.38

A sub-chronic (90-day) toxicity study was done with a different strain of rats with much lower doses in feed to assess safety for the food additive industry.39 Because this study did not entail two years of dosing nor two animal species, it was not a carcinogenicity study. Nonetheless, the results “were indicative of the target organ toxicity pattern that at higher intake levels, such as those tested in the NTP studies, produces more severe toxicity and leads to associated neoplastic lesions.”40 The cannabis industry sometimes claims that β-Myrcene is harmless because it occurs naturally in certain foods such as carrots and hops. This claim is specious. Very small amounts of naturally-occurring compounds can be lethal, including castor beans (ricin), mushrooms such as Amanita phalloides (α-amanitin), and sprouted potatoes (glycoalkaloids). Some compounds that are vital for health or useful as medicines in small amounts are lethal at high concentrations. Examples include vitamin D, vitamin A, iron, warfarin, and sodium chloride. The concentrations of β-Myrcene in carrots and in beer made with hops are many orders of magnitude lower than what humans can be exposed to from cannabis plant emissions. A human would need to consume each day 300 pounds of carrots or drink 1,400 beers to equal the amount of β-Myrcene inhaled in one day at 100 parts per billion (ppb) β-Myrcene.41 “The dose makes the toxin.”

Inhalation of terpenes is potentially more threatening to human health than ingestion because inhaling increases bioavailability.42 “Brain exposure of a molecule via the blood can be significantly lower than exposure resulting from direct brain exposure of the molecule by inhalation because of metabolism, distribution into other body organs/tissues, and difficulty in crossing the blood brain barrier.”43 Moreover, “exposure by inhalation may cause brain toxicities not seen in the rodent toxicity studies” because there are no toxicity studies on inhalation.44

2. Calculating Toxic Levels and Carcinogenicity of β-Myrcene.

Toxic levels in humans can be calculated using conversion from toxic levels in animal studies to equivalent human dosing levels, using well-accepted conversion factors employed by the pharmaceutical industry, toxicologists, and the FDA.45 The calculations must account for the higher bioavailability of inhalation versus oral ingestion and predicted accumulation in humans.46 The calculated human-equivalent toxic doses of β-Myrcene reflect body weight and are 3.5 mg/day for a 15 kg person (e.g., a 33 pound 3-year-old) and 14 mg/day for a 60 kg person (e.g., a 132 pound adult).47 These doses are the human-equivalent to the lowest dose tested in mice, which was highly carcinogenic after two years of exposure. Toxic effects on kidney and liver in rodents were observed within three months.48

Because β-Myrcene was carcinogenic at the lowest dose tested in rodents, no lower, non-toxic dose could be determined.49 Thus, further dose reductions are needed to estimate toxic and safe exposure levels for chronic exposure. As noted above, it is standard to use a one-tenth reduction to estimate a lower “toxic” level. Using this and a 50% absorption of β-Myrcene from air yields a calculated “safe” exposure level of 0.5 ppb for the child and 2 ppb for an adult.50 “Safe” exposure levels for infants and developing fetuses logically might be much lower.51 These illustrative calculations show that β-Myrcene can pose a serious health threat.

3. Estimating Safe Human Exposure Levels of β-Myrcene.

Another accepted approach for determining safe human exposure levels or Occupational Exposure Limit (OEL) of β-Myrcene in the air uses the formula OEL = POD/ (AFc x a x S x MF x V).52 Using the rat data, this estimates a “safe” exposure level of 2.7 ppb for a child and 10.7 ppb for an adult.53

4. Level of Exposures to Cannabis Emissions.

The threshold of human odor detection of cannabis emissions provides good information about the levels of cannabis emissions, including β-Myrcene, to which neighbors of CCOs are exposed. A study of human odor detection in Santa Barbara County found that when “terpene concentrations range between 20 and 50 ppb, greater than half of the participants report odors.”54 Thus, when residents of Kern County and Nevada County, California, reported detecting cannabis odors 1 and 2 miles away from cultivation sites the strong implication is that the levels of β-Myrcene were at least in the 20-50 ppb range.55 Moreover, cannabis emissions can be analyzed with quantitative scientific methods in real time in the field using gas chromatography, which avoid human subjective determinations. Emissions measured 2,600 feet from a 4-acre grow were 440 ppb.56 There is a critical need for additional site-specific empirical assessment with confirmation testing to allow regulatory agencies to set standards for unhealthy and hazardous cannabis emissions.57 Concentrations of β-Myrcene are generally correlated to distances from a CCO and are generally higher when the affected site is downwind. When humans detect cannabis odors, they are probably inhaling levels of β-Myrcene that exceed 20-50 ppb. When the odor is strong, β-Myrcene can be orders of magnitude higher than 20-50 ppb. Unregulated and unhealthy emissions from outdoor CCOs (or from indoor CCOs if emissions are not properly filtered) can reach several thousand ppb of β-Myrcene.58

5. Harm From Exposure to Toxic and Carcinogenic Cannabis Emissions.

Residents near outdoor CCOs can be involuntarily exposed to toxins and carcinogens in their homes when cannabis emissions enter through windows and doors. They can breathe toxins essentially continuously for months at a time, year after year. Anyone who smells cannabis emissions is inhaling at least 20 ppb of β-Myrcene, which would rapidly enter the bloodstream. The longer the exposure and the higher the concentrations, the greater the risk of toxicity and cancer. The amount of β-Myrcene inhaled during a single growing season may be toxic to the liver and kidneys and over several years can exceed the carcinogenic dose determined through controlled tests with animals. Chronic exposure to a compound generally causes toxicity at much lower doses than observed for acute exposure.59 At 100 ppb, children are exposed to toxic doses of β-Myrcene that can cause liver and kidney damage after only three months, and adults after 12 months.60 Even at ambient levels of only 10 ppb, which is generally below the level of human odor detection, children are exposed to toxic doses after five years if the exposure to β-Myrcene is six months per year; it approaches the projected toxic levels for adults after 10 years.61 Exposures can vary depending on the number of harvests per year, whether a particularly high-emitting cannabis varietal is cultivated, and site-specific geographic and weather conditions that may expose humans to even higher levels if they are located downwind of a CCO when plants flower.62

The cumulative levels of β-Myrcene that neighbors can be involuntarily exposed to is significant, may cause toxic effects, and ultimately may be carcinogenic.

Dr. George Rutherford, a distinguished Professor Emeritus at UC San Francisco, concluded that regulators should “seriously consider the toxic and carcinogenic effects of β-Myrcene to which residents are exposed involuntarily and act in a way to protect the public health.”63 Dr. Rutherford is a former State Epidemiologist and State Health Officer for California as well as professor emeritus of Epidemiology, Preventive Medicine, Pediatrics and History at UC San Francisco and adjunct professor in the School of Public Health at UC Berkeley, with over 300 peer-reviewed publications.64 EPA should heed his advice and regulate emissions from CCOs.

V. DISCUSSION.

A. EPA Should Regulate CCOs Pursuant to CAA § 111.

Section 111 of the CAA requires the EPA Administrator to list a category of stationary sources if it “causes, or contributes significantly to air pollution which may reasonably be anticipated to endanger public health or welfare.” 42 U.S.C. § 7411(b)(1)(A). This petition seeks the addition of CCOs to the list of sources subject to regulation under § 111 because they meet the endangerment standard. In listing CCOs, the Administrator must use his judgment to determine that the CCO source category satisfies a two-part test. First, the Administrator must determine that air pollution of the kind emitted by CCOs “may reasonably be anticipated to endanger public health or welfare.” 42 U.S.C. § 7411(b)(1)(A). Second, the Administrator must determine that CCOs cause or contribute significantly to this air pollution. Id. It is clear from the facts presented above and the discussion below that CCOs are a stationary source category within the meaning of § 111, and that the air pollutants emitted by CCOs contribute significantly to air pollution problems that endanger public health and welfare.

The CAA does not require absolute scientific certainty or proof of actual harm when making an endangerment finding. Massachusetts v. EPA, 549 U.S. at 506 n.7. To the contrary, the Administrator must list CCOs and promulgate standards of performance if they “may reasonably be anticipated” to endanger public health or welfare. 42 U.S.C. § 7411(b)(1)(A) (emphasis added). The plain meaning of that phrase authorizes, if not requires, the Administrator to act to prevent harm and to act in conditions of uncertainty. The legislative history confirms that Congress wanted to “assure that regulatory action can effectively prevent harm before it occurs.”See Lead Indus. Ass’n v. EPA, 647 F.2d 1130, 1152, (D.C. Cir. 1980), citing H.R. Rep. No. 95- 294 at 49 (1977).

1. CCOs are “Stationary Sources” Within the Meaning of CAA § 111 and EPA Regulations.

CAA § 111 defines a “stationary source” as “any building, structure, facility, or installation which emits or may emit an air pollutant.” 42 U.S.C § 7411(a)(3) (emphasis added). EPA’s regulations under this provision use the term of art “facility” in the regulatory definition of concentrated animal feeding operations. 40 C.F.R. § 122.23 App. B (“an animal feeding operation where more than 1,000 'animal units' … are confined at the facility…” (emphasis added)). In this regard, CCOs are analogous to concentrated animal feeding operations. CCOs can have thousands if not tens of thousands of plants that emit harmful VOCs,65 while concentrated animal feeding operations typically have more than a thousand animals that emit harmful air pollutants. CCOs clearly meet the definition of a stationary source because they are “facilities” that emit air pollution.

2. CCOs Emit Harmful Air Pollutants Under the Clean Air Act.

As set forth above, the emissions from CCOs constitute air pollution that endangers health and welfare. CAA § 111 is not limited to regulating criteria pollutants and their precursors; EPA has the authority to promulgate performance standards for pollutants “for which air quality standards have not been issued or which are not included on a list” under § 108(a) or § 112(b)(1)(A). 42 U.S.C. § 7411(d). The air pollutants emitted by CCOs meet the statutory definition of “air pollutant” under the Act. Specifically, CCOs emit certain VOCs (terpenes, including the toxin/carcinogen β-Myrcene) that endanger human health. The CCO air emissions described above are air pollutants under the plain language of the CAA and the “ordinary, contemporary, common meaning” of the term because they are emitted into the ambient air. Perrin v. U.S., 444 U.S. 37, 42 (1979), citing Burns v. Alcala, 420 U.S. 575, 580-581, (1975); See Consumer Product Safety Commission v. GTE Sylvania, Inc. 447 U.S. 102, 108 (1980) (“the starting point for interpreting a statute is the language of the statute itself”). The Act defines an “air pollutant” as an air pollution agent or combination of such agents, including any physical, chemical, biological…substance or matter which is emitted into or otherwise enters the ambient air. Such term includes any precursors to the formation of any air pollutant…” 42 U.S.C. § 7602(g).

Courts have generally interpreted the definition of “air pollutant” broadly. See Alabama Power Co. v. Costle, 636 F.2d 323, 352 n. 60 (D.C. Cir. 1979); Massachusetts v. EPA, 549 U.S. 497, 528 (2007) (the definition of an “air pollutant” is “sweeping”). When Congress used expansive language in the CAA’s definition of “air pollutant,” it intended a broad grant of authority to EPA. Massachusetts v. EPA, 549 U.S. at 528. The Court also stated that “[o]n its face, the definition [of ‘air pollutant’] embraces all airborne compounds of whatever stripe, and underscores that intent through the repeated use of the word ‘any.’” Id. at 529.

The terpenes emitted by CCOs plainly meet the sweeping statutory definition of “air pollutant” under 42 U.S. Code § 7602(g). While neither EPA nor the courts have established a standard for determining a “significant contributor” to air pollution, the growing number of CCOs, the startling quantity of dangerous VOCs that CCOs can produce and inflict upon neighbors, and the severity of the air pollution problems associated with those emissions is strong evidence that CCOs are “significant contributors” to air pollution. National Asphalt Pavement Association v. Train, 539 F.2d 775, 784 (D.C. Cir. 1976).

Odors and associated physical manifestations (e.g., respiratory irritation, asthma, nausea, headache) constitute some of the major public complaints about outdoor CCOs and have been linked to the presence of significant levels of VOCs. VOCs are present with all types of cannabis production methods. Pursuant to the requirements of CAA § 111, CCOs must be listed as a category of sources because these air pollution problems endanger public health and welfare. 42 U.S.C. § 7411(b)(1)(A). Even if additional research linking negative health and environmental impacts with CCOs should be undertaken, the CAA does not require absolute scientific certainty or proof of actual harm when making an endangerment finding. Massachusetts v. EPA, 549 U.S. at 506 n.7. The Administrator must list CCOs and promulgate standards of performance if they “may reasonably be anticipated” to endanger public health or welfare (emphasis added). 42 U.S.C. § 7411(b)(1)(A). The plain meaning of that phrase authorizes, if not requires, the Administrator to act to prevent harm and to act in conditions of certainty. The legislative history behind that language supports the notion that Congress wanted to “assure that regulatory action can effectively prevent harm before it occurs.” See Lead Indus. Ass’n v. EPA, 647 F.2d 1130, 1152, (D.C. Cir. 1980), citing H.R. Rep. No.95-294 at 49 (1977).

The Supreme Court found that EPA cannot refuse to regulate “by noting the uncertainty surrounding various features” of air pollution. Massachusetts v. EPA, 549 U.S. at 534. There is more than enough scientific evidence to meet the ndangerment standard for unhealthy emissions from CCOs. Studies document instances of respiratory illness, lung inflammation, and increased vulnerability to respiratory diseases, such as asthma” among the effects CCO emissions can have on human health.66 The cannabis industry is aware that these problems can harm workers. As depicted elsewhere, it is common for workers within CCO facilities to wear full body protective gear and masks to avoid serious respiratory problems. Unfortunately, two cannabis workers have died from occupational asthma from exposure to unhealthy emissions from cannabis.67 Children and teenagers who attend school or have homes near CCOs may be at higher risk for asthma. Many jurisdictions require minimum setbacks from schools to protect children while ironically imposing lesser setbacks to their homes where they spend much more time.68 In rural areas, children of economically-challenged farm workers are often the most affected population. Evidence shows that CCOs, especially outdoor operations, pose a risk to human health and welfare. The VOC emissions from CCOs meets the endangerment standard as well. Regulating unhealthy VOC emissions will reduce risks to human health caused by CCOs.

3. The Administrator Must Exercise His Authority under CAA § 111 to List and Promulgate Performance Standards for CCOs.

Outdoor CCOs (and indoor CCOs that fail to employ adequate exhaust air cleansing systems) are a public health threat to neighbors and others who involuntarily breathe toxins and carcinogens. CCOs contribute significantly to air pollution which may reasonably be anticipated to endanger public health or welfare. 42 U.S.C. § 7411(b)(1)(A). CCOs meet the definition of a stationary source under the Act, and therefore are eligible for listing. See 42 U.S.C §§ 7411(a)(3), (b)(1)(A). The CAA is a precautionary statute and “demand[s] regulatory action to prevent harm, even if the regulator is less than certain that harm, is otherwise inevitable.” Ethyl Corp. v. EPA, 541 F.2d 1, 25, (D.C. Cir. 1976). Section 111 was designed to “emphasize the precautionary or preventative purpose of the act (and, therefore, the Administrator’s duty to assess risks rather than wait for proof of harm).”69 Because of the serious consequences caused by unhealthy emissions from CCOs, the Administrator should take immediate action to regulate CCO emissions under § 111.

Once the Administrator finds that CCOs contribute significantly to air pollution that endangers public health or welfare, no discretion exists as to whether he must regulate such emissions from this industry under CAA § 111. Nat’l Res. Def. Council, Inc. v. Train, 411 F.Supp. 864, 868 (S.D.N.Y. 1976). Because of the large amounts of dangerous pollutants from CCOs, like other categories of stationary sources regulated under § 111, EPA must list them as a category of sources under § 111. “A long line of precedent has established that an agency action is arbitrary when the agency offered insufficient reasons for treating similar situations differently.” Transactive Corp. v. U.S., 91 F.3d 232, 237 (D.C. Cir. 1996); see also Indep. Petroleum Ass’n of Amer. v. Babbitt, 92 F.3d 1248, 1258 (D.C. Cir. 1996) (“An agency must treat similar cases in a similar manner unless it can provide a legitimate reason for failing to do so.”).

The Neighborhood Coalition requests that the Administrator list this industry under CAA §111, based on currently available scientific data demonstrating that unhealthy CCO emissions contribute significantly to air pollution. The Administrator also must issue new and existing CCO performance standards and consider issuing secondary standards to protect public welfare.

4. A National Approach Using CAA § 111 to Regulate Air Pollutant Emissions from CCOs Is Necessary and Feasible.

Under the existing regulatory approach, state and local authorities are doing little, if anything, to protect the public from CCO emissions. The CAA was enacted in part to address the concern that states can compete for economic development by having low environmental standards to attract mobile capital and businesses seeking lower compliance costs.70 This phenomenon is sometimes called the "race to the bottom."

This may be occurring in California, which has an economic interest in fostering outdoor CCOs to produce affordable marijuana that can eventually be sold nationwide. California’s Department of Cannabis Control has been aware of the problems with toxic cannabis emissions for years, but has done nothing to address this problem. For example, the Department of Cannabis Control in December 2025 awarded $30 million in cannabis research grants, none of which even study toxic cannabis emissions.71 Currently California residents must invoke nuisance laws to try to protect themselves from CCOs. A class action nuisance case in Santa Barbara County is scheduled for trial in 2026.72 Neighbors filed suit in Petaluma to enjoin a CCO that caused significant breathing problems for neighbors, including a young paraplegic who needed a breathing tube to avoid suffocation.73 The purpose of the CAA is “to protect and enhance the quality of the Nation's air resources so as to promote the public health and welfare . . . .” 42 U.S.C. § 7401(b). EPA should set nationwide minimum emissions standards under CAA § 111 to protect individuals and communities. Neighbors should not have to pay for expensive nuisance suits to protect themselves from commercial operations that spew toxic and carcinogenic emissions. The vast majority cannot afford the legal fees

A national approach is especially needed now because marijuana has recently become legal in most states.74 Hemp has been widely cultivated to produce CBD since Congress legalized industrial hemp in 2018. The Drug Enforcement Administration will soon reschedule marijuana under the Controlled Substances Act,75 encouraging even more CCOs. Setting national performance standards will address risks to public health and welfare by setting minimum emissions limits at levels that ensure safety and promote the public health and welfare. County, city, and state authorities cannot be trusted to protect public health and welfare. They often stymy such protections to foster economic development or to enrich the families of public officials or their donors.

Setting CAA § 111 performance standards can reduce emissions from CCOs. Relevant technologies include design, equipment, work practice, and operational standards. 42 U.S.C. § 7411(h)(1). Pollution reduction can be achieved through a variety of means and is not limited to end-of-pipe controls. Simple work practice changes might significantly reduce unhealthy emissions from CCOs. For example, requiring minimum distances of CCOs from residences and businesses and requiring site-specific air quality studies to establish setbacks would reduce exposures.

If work practices fail to prevent exposures to unhealthy emissions, EPA could ban outdoor CCOs altogether. Marijuana could be required to be grown indoors or in greenhouses where facilities could be required to install and operate well-maintained filtration systems. Demonstrated technology can capture and reduce unhealthy emissions by 95% or more to prevent terpenes from exiting a structure. Such systems can include spraying fog or mists with chemicals into the air to destroy terpenes, along with charcoal or high efficiency particulate and VOC filtration devices. Continuous emission monitors to measure terpenes are available, analogous to what EPA has required for electric steam generating units for 40 years. Indoor CCOs must have mandatory maintenance criteria and enforceable shutdowns if they fail to achieve the performance standards.

Best demonstrated technology is continually being updated, and current technology and work practices are sufficient to set standards. Courts have routinely agreed that “adequately demonstrated” does not mean that the facilities must already be capable of achieving standards. CAA § 111 “looks toward what may fairly be projected for the regulated future, rather than the state of the art at present…” Portland Cement Ass’n v. Ruckelshaus, 486 F.2d 375, 391 (D.C. Cir. 1973). The technologies and work practices discussed above can provide significant reductions in unhealthy CCO emissions while new technologies are being developed.

B. EPA Should List β-Myrcene as a Hazardous Pollutant Under CAA § 112.

For similar reasons as those for regulating CCOs under CAA § 111, the Administrator should add β-Myrcene to the Hazardous Air Pollutant list under CAA § 112. The Neighborhood Coalition is confident that the information contained in this petition demonstrates that that there are ample data showing “adverse effects to human health,” CAA § 112(b)(3)(B), resulting from exposure to β- Myrcene. Animal data have shown liver and kidney toxicity and clear evidence of carcinogenicity. The potential exposure of the general public and sensitive subpopulations to unregulated emissions from CCOs is adequate to support the listing of β-Myrcene as a Hazardous Air Pollutant under CAA § 112(b)(3)(B).

VI. CONCLUSION.

Mitigating the cannabis industry’s significant yet underappreciated role in air pollution problems is vital for the health and sustainability of the communities where they operate. The negative impacts from unhealthy outdoor CCO emissions are already occurring and will only worsen as more marijuana and hemp are grown. Scientific consensus supports immediate listing of CCOs, the issuance of new source performance standards for the industry, and the listing of β-Myrcene as a Hazardous Air Pollutant. Based on the information contained in these petitions, the Administrator should determine that CCOs and β-Myrcene contribute significantly to air pollution that endangers public health and welfare.

For all these reasons, EPA should (1) list CCOs under CAA § 111; (2) promulgate standards for new, modified, and existing CCOs under CAA § 111; and (3) list β-Myrcene as a hazardous air pollutant under CAA § 112.

Respectfully Submitted,

Neighborhood Coalition

P.O. Box 1229

Sebastopol, CA 95473

Dr. Deborah Eppstein

Craig S. Harrison

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Attached document contains all exhibits

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