Highly elevated PM10 values were observed at the Dunham downwind monitor: a maximum hourly concentration of 6,500 µg per cubic meter occurred from 1:00 to 2:00 p.m., then a dramatic decline to 4.3 µg per cubic meter by 4:00 p.m. The average 24-hour PM10 concentration at this Dunham location was 276 µg per cubic meter, well above the federal criteria for unhealthy air, 150 µg per cubic meter . Although we only successfully deployed one monitor, the highly elevated concentrations were consistent with PM10 levels reported in another study of a burned field . Photo evidence was also consistent with visibility of less than 1 mile, which is expected at hazardous air levels . As noted, wind speed at this burn was somewhat higher than at the other burns . At several of the other 12 nephelometer locations, much smaller peaks were apparent in PM2.5 and PM10 after the burns were initiated, up to 57 µg per cubic meter of PM10 within the hour. Similar to the E-BAM findings, evening-to-morning peaks in PM2.5 and PM10 were observed. Although all of these peaks were relatively brief , these measurements were collected at places of public access, and even short-term exposures may have health risks. An increase in PM2.5 concentrations in air samples from city centers as low as 10 µg per cubic meter for as little as 2 hours has been associated with increased daily mortality in the surrounding population .At the laboratory, computer-controlled scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to obtain the individual sizes and chemistry of particles collected on the samplers. Then, PM2.5 and PM10–2.5 concentrations and particle size distributions were calculated using assumed particle density and shape factors and a particle deposition velocity model . In samples from the downwind locations at the Dunham burn, concentrations of both PM2.5 and PM10–2.5 were elevated compared to an upwind sample. The fine fraction was primarily carbonaceous with a peak at the submicron range ,commercial vertical farming while the coarse fraction had a lower carbonaceous percentage .
These carbonaceous percentages were higher than those measured upwind for fine and coarse fractions, as well as those reported for fine and coarse fractions in San Joaquin Valley ambient air . The coarse fraction in the downwind sample also had higher percentages of potassium, phosphorus and chlorine . Potassium and chlorine are considered potential indicators of biomass smoke , and phosphorus is found in most plant material. We also analyzed samples of unburned and burned bermudagrass and found that among inorganic elements, they contained similar peaks of potassium, phosphorus and chlorine . Their identification here may assist air pollution researchers attempting to identify sources of particulate matter in air samples. Samples were analyzed for vapor-phase naphthalene by gas chromatography/mass spectroscopy. Concentrations were calculated using an established air-sampling rate. Naphthalene was occasionally detected at the five targeted burns with levels above the reportable limit at seven of the 23 locations near the burns and at one of the six more-distant locations .That highest level was lower than a reference level for respiratory effects , but only two samples were collected directly downwind and concentrations elsewhere in the plume could have been higher or lower. To compare, vapor-phase naphthalene measured in a laboratory from directly above the burning of agricultural debris was 60 µg per cubic meter . Responses from our key informants indicated that educational messages were needed. We developed two-page fact sheets for three Imperial County audiences — the general public, school representatives and farmers. These covered the reasons for burning, burn regulations, potential health impacts and behavioral recommendations to reduce exposures.
In our studies, elevated particulate matter levels and visible drift were observed as far as 500 feet from the edge of burning fields, and wind directions could quickly change. We advised that anyone who could see or smell smoke or was within 300 feet of a burning field should go inside. If people had to be outside near a burning field, we recommended face-piece particulate respirators , which are available at most hardware stores. A worker who must be outdoors and near a burn must be in a respiratory protection program that includes medical evaluations and fit-testing of the respirator’s seal on the worker’s face . A draft of the fact sheet for the general public was tested with community members at a health clinic and shopping center. Although there were complaints about its length, the fact sheet was highly rated for usefulness: all 20 participants gave it either a four or a five on a scale of one to five . The final fact sheets were distributed to local organizations and are available on the Internet .In our studies, agricultural burning created potentially hazardous air levels immediately downwind; during evening-to-morning hours, PM2.5 levels increased 2 to 8 µg per cubic meter. Many studies have associated total daily human mortality with mean daily particulate matter levels measured in urban centers, and some have observed a relationship at levels as low as 2 µg per cubic meter . In California, increases in children’s total daily hospital admissions for respiratory problems are also associated with increases in daily PM2.5 and potassium air levels, the latter an indicator of biomass smoke . To protect public health and potentially reduce exposures to smoke from agricultural burns, we recommend additional health education, smoke management and air quality research. Currently, CARB declares a permissive-burn day when meteorological conditions ensure the regional dispersion of smoke, for example, a wind speed at 3,000 feet of at least 5 miles per hour . Imperial County’s smoke management plan states that the Air Pollution Control District may put in place additional restrictions based on meteorological and air quality conditions, including strong ground-level or gusty winds . We observed substantial drift at a slightly greater wind speed than that previously suggested for a vertical column of smoke to occur . Local Air Pollution Control Districts could reduce ground level drift by specifying a ground-level wind speed above which burns should not take place. Additionally, evening to-morning levels of particulate matter could be reduced if warranted by other restrictions, such as shortening allowable burn hours. Interviewed residents expressed reluctance to report neighbors who might be out of compliance.
Supplemental Imperial County Air Pollution Control District activities could include online instructions about how to make a complaint. In addition, posting visibility guidelines for hazardous drift and a daily listing of the areas in the county where burns were scheduled would improve community notification.Additional air monitoring is needed to further characterize the nature and extent of ground-level plumes and how they are affected by local crop type and conditions. Although crop-specific particulate emission factors from burning bermudagrass stubble have not yet been developed, factors for other grasses, such as Kentucky bluegrass,mobile rack systems are about twice those for rice and wheat . The moisture level of burned residue can also significantly affect particulate matter emissions, with a change in moisture from 10% to 25% more than tripling particulate emissions during the burning of rice, wheat and barley straw . Ambient monitoring should also include indoor air, as outdoor PM2.5 may substantially infiltrate buildings , and we observed that outdoor particulate matter increases overnight when people are likely to be inside. Residents may be amenable to researchers installing unobtrusive passive samplers to monitor indoor air. In further studies, methods might be modified to allow the further identification of carbonaceous material, the gaseous component of other PAHs and some of the thousands of other volatile gases found in smoke . Information is also needed on whether residents are following recommendations to reduce their exposure to smoke from agricultural burning. Finally, farmers expressed a willingness to try alternative farming practices, notably tilling. We recommend further study of alternative farming techniques such as conservation tillage, which may reduce the need for burning, conserve water and soil, and reduce air quality impacts . In addition, integrating livestock grazing with grain and hay farming as a substitute for burning or tilling may reduce pests, herbicide use and erosion and provide additional income . Further study is needed on how farmers could viably integrate alternative techniques into current practices, particularly for local crops such as bermudagrass, and the estimated human health impacts of such changes. With the passage of Proposition 64 , state voters elected to integrate cannabis into civil regulation. The California Department of Food and Agriculture oversees state-licensed cannabis cultivation and defined it as agriculture . Prior to the possibility of state licensure for cultivators, however, counties can decide on other designations and implement strict limitations. In effect, local governments have become gatekeepers to whether and how cultivation of personal, medical or recreational cannabis can occur and the repercussions of noncompliance. When cannabis is denied a consistent status as agriculture, despite being a legal agricultural commodity according to the state, localities can determine who counts as a farmer and who is considered compliant, non-compliant and even criminal. In Siskiyou County’s unincorporated areas, the Sheriff’s Office now arbitrates between the effectively criminal and agricultural.
Paradoxically for this libertarian county, the furor around cannabis has seen calls for government intervention, and has led to officials passing highly stringent cannabis cultivation regulations that have been enforced largely by law enforcement, muddying the line between noncompliance and criminality. These strict regulations produced a situation where “not one person” has been able to come into compliance, according to a knowledgeable government official. Nonetheless, at the sheriff’s urging, Siskiyou declared a “state of emergency” due to “nearly universal non-compliance” , branding cannabis cultivation an “out-of-control problem.” Such a strong reaction against cannabis can be understood in terms of cannabis’s potential to reorganize Siskiyou’s agricultural and economic landscape. According to some estimates, there are now approximately twice as many cannabis cultivators as non-cannabis farmers and ranchers in Siskiyou , a significant change from just a few years ago. Although cannabis has been cultivated in this mostly white county for decades, since 2015 it has become associated with an in-migration of Hmong-American cultivators. Made highly visible through enforcement practices, policy forums and media discourses, Hmong-Americans have become symbolically representative of the “problem.” This high visibility, however, obscures a deeper issue, what Doremus et al. see as a nostalgic, static conception of rural culture that requires defensive action as a bulwark against change. Such locally-defined conceptions need to be understood , especially in how they are defined and defended and what effects they have on parity among farmers growing different types of crops. Our goals in this study were to consider the consequences of an enforcement-first regulatory approach — a common regulatory strategy across California — and its differential effects across local populations. Using Siskiyou County as a case study, we paid attention to the public agencies, actors and discourses that guided the formation and enforcement of restrictive cannabis cultivation regulations as well as attempts to ameliorate perceptions of racialized enforcement. This study attends to novel post legalization apparatuses, their grounding in traditional definitions of culture and the ways these dynamics reactivate prohibition. We used qualitative ethnographic methods of research, including participant observation and interviews. In situations of criminalization, which we define not only as the leveling of criminal sanctions but being discursively labeled or responded to as criminal-like , quantitative data can be unreliable and opaque, which necessitates the use of qualitative ethnographic methods . In 2018–2019, we talked to a wide range of people — including cannabis growers from a diversity of ethnic backgrounds, government officials, business people, subdivision residents, farm service providers, medical cannabis advocates, realtors, lawyers, farmers and ranchers, and, with the assistance of a Hmong-American interpreter, members of the Hmong-American community. We also analyzed public records and county ordinances, Board of Supervisors meeting minutes and audio , Sheriff’s Office press releases and documents, related media articles and videos, and websites of owners’ associations in the subdivisions where cannabis law enforcement efforts have focused. Some cannabis cultivators regarded us suspiciously and were hesitant to speak openly, an unsurprising phenomenon when researching hidden, illegal and stigmatized activities, like “drug” commerce . This circumspection was most intense among Hmong-American growers on subdivisions, who had been particularly highlighted through enforcement efforts and local, regional and national media accounts linking their relatively recent presence in Siskiyou to cannabis growing.