Organic Contaminants at Trespass Cannabis Grows on Federal Land in California, USA

Despite the legalization of recreational cannabis in California, illegal cultivation persists, particularly on public lands (trespass grows). These operations often divert water unlawfully and apply unauthorized chemical fertilizers and pesticides. This dataset reports the presence, and in some cases concentrations, of persistent chemicals in soil, water, and sediment in nearby streams. We conducted quantitative analyses of 183 pesticide compounds in water and 176 in soil/sediment, along with qualitative nontargeted screening at three trespass sites inactive for 8 months to 2 years. Targeted analysis revealed insecticides like bifenthrin, cyfluthrin, malathion, and imidacloprid (up to 38 nanograms per gram (ng/g) dry weight (d.w.)) and fungicides such as fluopyram, myclobutanil, and triadimefon (up to 8.1 ng/g d.w.) in soil, but no pesticides were found in water or sediment samples. Nontargeted screening detected additional pesticides (e.g., spiromesifen, trinexapac) in soil and cannabis-related compounds (e.g., cannabidiol, delta-9-tetrahydrocannabinol) in both soil and sediment, indicating potential offsite transport. Phthalate plasticizers, rubber-related compounds, and pharmaceuticals were also found in soil, water, and sediment, likely linked to extensive irrigation infrastructure at these sites. This dataset establishes a contaminant profile associated with illegal cannabis cultivation, laying the groundwork for future studies on ecological impacts.