Despite high AR exposure levels , both studies reported very low numbers of animals dying primarily from AR exposure. Nevertheless, AR poisoning may significant impact mortality rates in Californian fisher populations , with increasing prevalence from 2007 to 2014. AR contamination is not limited to mammals. It was also documented in northern spotted owl and barred owl populations, likely through secondary poisoning from predation on contaminated rodents . Despite some limitations due to small sample sizes , these studies draw attention to a potential ecological threat posed by illicit cultivation methods. Far less is known about application of chemicals in legal growing operations, which vary greatly by region and country. While some ARs are illegal or heavily restricted in the United States, various other pest-control methods have been reported for cannabis . In the US, due to the crop’s federally illegal status, no commercially available pesticides have been approved for use on cannabis . In Canada, 25 pesticide and fungicide compounds have been approved for legal use on cannabis.Wang, et al. measured biogenic volatile organic compounds emitted by cannabis plants grown under conditions mimicking greenhouse cultivation. Results suggested BVOC emissions from indoor cultivated cannabis in Colorado could contribute to ozone formation and particulate matter pollution. The authors acknowledged limitations due to small sample sizes, sub-optimal growing conditions, and a focus on only 4 out of 620 reported cannabis strains. In a follow-up study, Wang, et al. estimated terpene emissions and regional ozone impacts from indoor cannabis cultivation facilities in Colorado using the Comprehensive Air Quality Model. Results predicted increases in hourly ozone concentrations which may have consequences for regional air quality. This approach was limited by reliance on estimates and assumptions in the absence of data regarding emission capacity of most cannabis strains, number of plants and plant biomass. Nevertheless, preliminary findings indicated that concentrated indoor cannabis cultivation could influence ozone pollution through BVOC emissions from terpenes,seedling grow rack particularly in areas where nitrogen oxides are not the limiting factors in ozone formation.

Surface- and ground-water pollution from the cannabis industry, including from soil erosion, pesticide and fertilizer in run-off, chemical processing or waste disposal operations, is a likely risk . Nevertheless, we found no peer-reviewed study quantifying the impacts of cannabis cultivation on water quality, although current pilot projects in California are underway. We did find an academic book series and five peer-reviewed publications documenting the effects of pollution from cannabis consumption on water quality. These studies used THC-COOH concentrations in sewage systems, presumably originating from human consumption, as a proxy. Evidence of THC-COOH presence was found in both raw and biologically treated wastewater across major European cities as well as in raw wastewater in the US . Concentrations of chemical compounds derived from cannabis were lower in treated than in raw wastewater. Nevertheless, accumulation of these compounds may contribute to waterway contamination downstream from wastewater effluent discharges in urban areas, although likely to a lesser extent than other illicit drugs . While these studies primarily aim to document urban cannabis consumption, they also point towards potential contamination issues impacting downstream freshwater ecosystems. Our current understanding of the consequences of wildlife exposure to cannabis-related chemicals remains limited. Parolini, et al. sought to bridge this gap through experimental exposure of zebra mussels to concentrations of cannabis active compounds Δ-9-THC and THCCOOH. Results showed that prolonged exposure could contribute to oxidative and genetic damage in the mussels. Still, given the lack of knowledge regarding actual Δ-9-THC and THCCOOH concentrations in aquatic ecosystems, and the lack of documentation of the compounds’ effects on mussels or other organisms in the wild, it is difficult to draw broader conclusions about potential environmental risks posed by exposure to active compounds in cannabis for aquatic organisms. Because there are environmental trade-offs across production methods, it is important for policy makers to consider the potential unintended consequences of policy decisions. For example, in California, stringent water-use regulations for outdoor production may incentivize cultivators to turn to alternative indoor production methods. While this shift may alleviate water-stress in sensitive ecosystems, it may also increase the carbon footprint of cannabis by encouraging energy-intensive indoor production.

Identifying and understanding trade-offs within and across systems is thus important, and cannabis regulation should be comprehensive in order to prevent impacts from being displaced from one pathway to another. The emerging literature on cannabis and the environment already provides useful insights to guide policy. Still, the majority of studies reviewed here were individual case studies, mostly geographically centered in Northern California. There is a tremendous need for similar studies to be carried out across different biophysical, socioeconomic, historical and cultural contexts, both to confirm the generalizability of these results and to avoid exporting environmental problems from the developed to the developing world. We expect that continued liberalization worldwide will provide expanded geographic scope for this work for years to come, and researchers should be ready to act on this expansion. Most of the literature reviewed here relies on observational or model-based methodologies . While these approaches provide insights, experimentation is fundamentally needed to understand basic agroecological functions and processes governing cannabis cultivation. Trials quantifying the energy footprints, water use, and nutrient requirements of different cultivation and management methods are also needed to improve the efficiency of production systems. Given increased liberalization trends, we expect to see a normalization of cannabis-related research. Scientists should be encouraged to carry out a range of experiments to bolster scientific capacity to assess the environmental impacts of an expanding cannabis sector. Additionally, as regulations around cannabis cultivation are implemented, long-term studies are needed to understand how these regulations affect cannabis cultivation practices. Cannabis cultivation may lead to additional environmental impacts, which remain scientifically undocumented to our knowledge. For instance, solid waste management of materials originating from cultivation, packaging, or other production processes, will need to be addressed. Life-cycle assessments of the cannabis sector could provide information on how to minimize such waste and more generally increase the efficiency and sustainability of cannabis production processes. Other potential areas for future research include odor pollution risks in communities where increased cannabis production has led to farms being sited near residential areas, cross pollination issues between cannabis and hemp , alternative cannabis farming or transportation efficiency. These topics, and many others, should make the study of cannabis’ environmental impacts a rich field for discovery for many years to come.

Traditionally, cannabis has been cultivated remotely and at small scales. Legalization is altering this through cultivation expansion, shifts toward urban areas, and increased size of production facilities , which may in turn affect the environmental impacts of the industry. The intensification of cultivation activities at large-scale facilities may magnify negative impacts. Conversely, economies of scale may increase the efficiency of larger facilities which may have broader capacities to invest in sustainable production processes. Larger facilities are also less likely to be located in remote sensitive areas than historical smaller farms, but may lead to land use trade-offs with other forms of agriculture. Continued diligence by policy makers and consumers is needed to ensure that the move towards industrialization is not a move away from sustainability – and researchers must continue to document shifts in the industry and their environmental impacts. In conjunction with legalization, social and ecological certification schemes could increase environmental performance of the industry. Emerging programs such as Sun and Earth Certification or planned appellation designations in California constitute first steps in this direction. By contributing to consumer awareness and providing incentives for growers to produce in sustainable ways, these programs may pave the way for the development of a more sustainable cannabis sector. In many ways, the question of how to best produce and consume cannabis while protecting the environment echoes larger debates about the environmental impacts of agricultural production in general. Current discourse on the optimal ways to address shifts in the cannabis sector touches upon fundamental sustainability framings such as land sparing vs. land sharing, intensification vs. expansion, technology-driven agriculture vs. agroecology,greenhouse growing racks the role of smallholder farmers vs. industrial-scale facilities. Policy makers working with cannabis have strong interests in developing effective regulations following legalization and are also dealing with regulatory “blank slates”. This may equip them with a novel combination of increased freedom and institutional capacity to test and evaluate the effectiveness of multiple policy approaches. Ultimately, failures and successes of environmental regulations for cannabis may lead to important lessons-learned for agriculture more broadly. Marijuana smoking was prevalent in this adolescent sample of tobacco smokers: 80% reported past month marijuana use and more than a third smoked marijuana daily. Notably, among adolescent tobacco smokers who also smoked marijuana, the frequency of marijuana use was associated with greater levels of nicotine addiction on all three major scales used in studies with adolescents plus the ICD-10. Moreover, models incorporating age, frequency and years of tobacco smoking with marijuana accounted for 25-44% of variance in adolescent nicotine dependence. Interestingly, CPD was only minimally associated with the frequency of marijuana use and made minimal contribution to the model since associations with the mFTQ were similar after removing the question about CPD.The finding that with the exception of drive and priority, the other sub-scales of the NDSS were not significantly associated with marijuana frequency was not surprising since most of these adolescent smokers were light and intermittent tobacco users and dimensions of dependence such as stereotypy and tolerance become more prominent as teens develop more regular and established patterns of smoking . However, despite relatively light tobacco use, the drive sub-scale, which measures the compulsion to smoke, and the priority sub-scale, which measures the preference of smoking over other reinforcers, were associated with marijuana use. It is possible that since both marijuana and tobacco share common pathways of use, smoking cues for one substance may trigger craving for the other, and thus reinforce patterns of use.

As such, tobacco and marijuana may serve as reciprocal reinforcers. Some limitations of this brief include the relatively small sample size and the lack of detailed information on the timing of the initiation of marijuana use with regard to cigarette smoking. Future studies will need to examine how the proximity of marijuana use to cigarette smoking affects the degree of nicotine addiction. For example, examining whether concomitant use impacts the level of nicotine addiction more than smoking marijuana separately from tobacco. The sample largely consisted of light smokers, which reflects adolescent smoking in the US. That we found such a strong association between marijuana use and nicotine addiction in this group of relatively light tobacco smokers is notable, and reinforces the relevance of the association.Large-scale prospective cohort studies of those at risk for or living with HIV have been instrumental in investigating research questions that could not otherwise be accomplished through smaller studies. A number of cohorts have been established going as far back as the start of the HIV epidemic in the mid-1980s. Some of the cohorts such as the multi-center AIDS cohort study were set up as a single study across multiple sites, implementing the same protocol with standard data collection tools, while other studies such as the North American AIDS Cohort Collaboration on Research and Design were designed as a collaborative in which 25 cohorts collect and integrate a common set of core information. Smaller cohorts have an important role in addressing questions in sentinel populations. In the absence of a common data collection effort such as those in MACS and NA-ACCORD, strategies that allow us to compile data across these individual studies can help us achieve comparable effects, increasing the impact of the data collected. Te Collaborating Consortium of Cohorts Producing NIDA Opportunities was established in 2017 by the National Institutes of Health/National Institutes of Drug Abuse to stimulate the use of NIDA longitudinal cohorts and to address high priority research on HIV/AIDS in the context of substance use . Tis consortium includes nine different cohorts located in the United States and Canada. All cohorts were established before the consortium was established, with the oldest having started in 1988 and the newest in 2015. All cohorts focus on HIV and substance use, however the target population, participant sampling strategies, as well as data collection tools differs for each of these cohorts.