Pesticides and Chesapeake Bay: Smoking Gun or Death by a Thousand - PowerPoint PPT Presentation

Pesticides and Chesapeake Bay: Smoking Gun or Death by a Thousand Cuts? Doug Myers – Maryland Senior Scientist Home to 17 Million People

What do we know about pesticide usage in the CB Watershed? What do we know about land delivery rates of pesticides in urban and agricultural runoff? What do we know about edge of tide concentrations of pesticides to Chesapeake Bay? What do we know about ecological effects of pesticide residues on Bay fauna at contact concentrations? What do we know about bioaccumulation and biomagnification of pesticide residues in the food web? What do we know about human health risk of consuming bay seafood?

What do we know about pesticide usage in the CB Watershed? • The most common chemical contaminants found in the Chesapeake Bay and its rivers and streams include polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), pesticides and mercury. – CB Program • This Network Produced a fine white paper compiling information on pesticide use: http://www.mdpestnet.org/wp-content/uploads/2012/11/MPN-2009WhitePaper.pdf • No Known updates to the 2012 government report that mostly uses 2008 data. But everyone should be familiar with this report: https://federalleadership.chesapeakebay.net/ChesBayToxics_finaldraft_11513b.pdf • According to MDA 2014 pesticide use inventory, nearly 5 million pounds of pesticides were used throughout Maryland. Herbicides accounted for 2.3 million pounds or 46 percent of total usage; insecticides accounted for 43 percent; and fungicides for 9 percent. https://mda.maryland.gov/plants- pests/Documents/MarylandPesticideSurveyPub.pdf • Recent studies are harder to come by. Recommendations of MD Pesticide Reporting Workgroup not implemented.

What do we know about land delivery rates of pesticides in urban and agricultural runoff? • Around 5.2 million tons of sediment enter the Chesapeake Bay in an average year. 2.5 million tons of that comes from agricultural land use. Uncovered construction sites can deliver 12X more sediment than an agricultural field per acre.- CB Model 5.3.2 • Pesticide residues are generally attached to eroding sediment particles because of drift. • Because of their low water solubility, organochlorine pesticides like DDT and its degradates persist in both sediments and biota for decades. • More modern pesticides have shorter half-lives, but are still detected in 10% of aquatic and estuarine sediments nationwide (dacthal, 2-4 DB, dicamba, diuron, trifluralin) – herbicides (chlorpyrifos, dicofol, endosulfan and lindane) – insecticides - USGS

What do we know about edge of tide concentrations of pesticides and their residues to Chesapeake Bay? Of the thousands of chemicals found in the sediments, fish, and water in the Chesapeake Bay, chlorpyrifos is one of the most concerning. Chlorpyrifos was found in more than 90 percent of water samples that were analyzed for this chemical and 40 percent of those had concentrations that exceeded thresholds indicating possible ecological effects. – CB Program Toxics Subcommittee

What do we know about ecological effects of pesticide residues on Bay fauna at contact concentrations? Not Much – Most recent published studies – 2008ish Most toxicology studies test individual chemicals in the lab, not mixtures found in the bay Risk analyses for threatened and endangered species consider these other factors, but EPA often ignores when considering registrations Chlorpyrifos toxicology studies suggest behavioral, reproductive and endocrine disruption to all aquatic arthropods, especially those in close proximity to chlorpyrifos runoff. Currently, only the Lower Patuxent River is listed as “impaired” by chlorpyrifos. Baltimore Harbor Watershed and 3 tributaries to the Anacostia are impaired for chlordane

What do we know about bioaccumulation and biomagnification of pesticide residues in the food web? EPA National Lake Fish tissue Survey BUT – Adult and juvenile Atlantic sturgeon in the Chesapeake are listed as endangered and, as NMFS notes, also are at high risk of harm from expected exposures to chlorpyrifos. Concentrations of the chemical in the Bay will reduce the spawning productivity and abundance of the fish.

Multiple Stressors? Marie DeLorenzo (NOAA) tested adult and larval grass shrimp, phytoplankton, and larval clams with pesticides commonly used to control insect, weed, and fungal pests. Then, she compared the toxicity of the chemicals using standard test conditions to toxicity under climate stress conditions (higher temperature, higher salinity, lower oxygen [hypoxia], and lower pH). In general, pesticides were more toxic under more extreme conditions than under conventional testing conditions. DeLorenzo’s results suggest that future risk assessments should take climate variables into account in determining the safety of pesticide use within the coastal zone. Marie and colleagues also found in a separate study - Agricultural pesticides were found to alter both functional and structural aspects of the estuarine microbial food web.

Conclusions: Death by a Thousand Cuts • Chesapeake Bay’s Ecology is in the process of a fragile recovery from pollution, over -harvest and habitat loss. • Pesticide residues from nearby urban and agricultural landscapes continue to pose a risk to that recovery, at least conceptually. • Pesticides don’t act alone in stressing individual bay critters or their predators. • Everything gets worse under future climate scenarios. • All levels of government are failing to provide understandable research reports on pesticide use trends and environmental effects

Other conclusions: Some things are getting better • Modern pesticides are far less persistent than older ones • Professional applicators are much better trained in IPM • Regenerative farm practices that reduce the need for pesticides are gaining traction in the watershed • Pesticide Advocacy is slowly working • The Bay is becoming more resilient

Chl Chlorpyri rpyrifos os While recent focus has been on the health impacts of chlorpyrifos, we have evidence to warrant concern about the impacts of chlorpyrifos on the Chesapeake Bay. To highlight a few of the findings I noted today:  Chlorpyrifos has been detected in 10% of aquatic and estuarine sediments nationwide.  Of the thousands of chemicals found in the sediments, fish, and water in the Bay, chlorpyrifos is one of the most concerning.  Chlorpyrifos was found in more than 90% of Chesapeake Bay water samples analyzed for this chemical and 40 % of those had concentrations that exceeded thresholds indicating possible ecological effects.  Chlorpyrifos toxicology studies suggest behavioral, reproductive and endocrine disruption to all aquatic arthropods, especially those in close proximity to chlorpyrifos runoff.