Polychlorinated Biphenyls (PCBs)
Landfills are one source of PCBs to local streams and rivers, where they build up over time in bottom sediments.
PCBs are a chemical contaminant found in some species of fish caught in parts of the Bay watershed. As they move up the food web, PCBs can have many negative health effects on humans, especially developing fetuses.
Where do PCBs come from?
Current and historic discharges from urban and industrial areas are the main source of PCBs in the Bay watershed. Other sources of PCBs include:
- Old electrical transformers
- Landfills and hazardous waste sites
- Circuit breakers, fluorescent light ballasts and other types of electrical equipment that contain electric insulating fluid
Even though the manufacturing of PCBs was banned in 1977, old PCB-containing equipment still in use can fail, causing the contaminant to flow into the nearest Bay tributary via stormwater. PCBs can also be released into the atmosphere as a vapor and then fall on cities, forests, rivers—and the Bay itself—via rain, snow or dry particles
How do fish become contaminated with PCBs?
PCBs build up over time in sediments at the bottom of streams and rivers and can persist there for many years. That is why PCBs that were discharged before the 1977 ban continue to impact the Bay today. Small, bottom-dwelling organisms take up PCBs as they feed near contaminated sediments. Fish and other animals then eat these small organisms, and the PCBs build up in their tissues. In turn, humans accumulate PCBs in their bodies when they eat contaminated fish.
A number of fish consumption advisories have been issued in parts of the Bay and its tributaries to prevent people from unknowingly eating fish that could be contaminated with PCBs.
What effects can PCBs have on human health?
PCBs have been shown in animals to cause cancer, as well as serious effects on the nervous, immune, endocrine and reproductive systems. Studies in humans have shown potential cancerous and non-cancerous effects. Women of child-bearing age are the population of greatest concern because of the toxic effects PCBs can have on developing fetuses, including low birth weight and a significant decrease in gestational age.