Toxic Pollution
While Casco Bay may look pristine, toxic pollution is present in its waters, in its sediments, and in the tissues of its living organisms, including clams, fish, birds and marine mammals. Toxics like heavy metals and organic contaminants can pose a threat to the health of aquatic life and humans.
Historic industries around Casco Bay — including shipyards, tanneries and textile factories — have left a legacy of toxic chemicals in the Bay’s sediment and waters. Today, nonpoint source pollution in the form of contaminated stormwater is the major contributor of toxic chemicals to the Bay. Pollutants are also deposited from the air via local and distance sources, in the form of rain or dust.
Toxic organic chemicals and some metals can increase in concentration as they move up the food chain. Those chemicals have the potential to disrupt the normal activity of hormones in mammals (including humans), causing cancer, adverse reproductive effects, birth and developmental problems, and effects on immune systems.
Studies have shown that mercury levels in Maine’s fish, loons, and eagles are among the highest in the country. Levels of this and other contaminants have led Maine to issue advisories and guidelines on safe fish and lobster consumption practices.
Despite evidence that toxic chemicals are found throughout Casco Bay and its watershed, there is some good news. The levels of mercury, PCBs, dioxins, and many pesticides entering the environment have declined greatly over the past two decades. Levels of most heavy metals, pesticides, tributyltin, PCBs and low molecular weight PAHs have decreased in the sediments of the Bay since 1991.
A new report commissioned by CBEP (link below) suggests some good news for Casco Bay: Concentrations of legacy pollutants – heavy metals and organic compounds such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) – tend to be declining. The Casco Bay Sediment Assessment 1991 – 2011, prepared by Ramboll Environ for CBEP, analyzed results from sediment monitoring of Casco Bay that was conducted from 1991 through 2011.
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Casco Bay Sediment Assessment 1991 – 2011
Casco Bay Estuary Partnership and Ramboll Environ
The Casco Bay Estuary Partnership (CBEP) has funded three comprehensive sediment quality assessments throughout Casco Bay since 1991, at roughly ten-year intervals. Chemicals analyzed include metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides, dioxins and furans, and organotins. This report summarizes the results from the most recent sediment sampling program conducted in 2010-2011 and describes how concentrations of chemicals in sediment have changed over the 20-year period since samples were originally collected.
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Casco Bay Sediment Assessment (Fact Sheet)
Casco Bay Estuary Partnership and Ramboll Environ
Since 1991, Casco Bay Estuary Partnership (CBEP) has sponsored a monitoring program to track the concentrations of certain pollutants in sediments throughout Casco Bay to answer the following questions:
- What are the concentrations of chemicals in Casco Bay sediments?
- Are chemical concentrations in sediment high enough to harm marine life?
- How have chemical concentrations in sediment in the Bay changed over time?
This fact sheet presents and interprets the results from sediment monitoring conducted from 1991 through 2011, the most recent year for which data are available. The sediment data show that concentrations for legacy pollutants tend to be declining throughout the Bay.
