Pollutant concentrations in US waters falling as reduction strategy takes effect
The US EPA is claiming success in its attempts to reduce concentrations of harmful pollutants in the ecosystems of the US' major water bodies, known collectively as the Great Waters.
The Agency says that, since the implementation of programmes to control the emission of pollutants, overall deposition rates of ‘pollutants of concern’ in the air, water, sediment and animal and plant life of the Great Lakes, Lake Champlain, Chesapeake Bay and specific coastal waters have declined slightly or remained constant.
The EPA’s Third Report to Congress on Deposition of Air Pollutants to the Great Waters focuses on 15 ‘pollutants of concern’, including certain pesticides, metal compounds, chlorinated organic compounds and nitrogen compounds.
The report finds that several pollutants of concern continue to enter the Great Waters primarily through atmospheric deposition. In addition, long-range transport of pollutants of concern from other US regions or other countries is estimated to contribute significantly to atmospheric loadings to the Great Waters. For example, the global reservoir of mercury – which includes mercury from both US and foreign sources – is estimated to contribute about 40% of the total mercury deposition to US lands and waters.
Concentrations of some pollutants of concern in the water, sediment and animal and plant life of the Great Waters declined in recent years, whereas others were constant or variable.
The report shows that deposition of lead, cadmium, polycyclic organic matter (POM), PCBs and some banned pesticides is declining in the Great Lakes. Other Great Waters have also shown decreasing trends of some pollutants, such as lead in Long Island Sound. Deposition of nitrogen has remained fairly constant across the US.
Emissions of mercury have been on a downward trend since 1990, according to the report, chiefly due to the phase out of mercury in many products.
Despite these figures, the EPA say concentrations of most pollutants of concern still pose potential adverse ecological and human health effects. For example, approximately five percent of the US’ coastal and inland watersheds include ‘areas of probable concern,’ which denotes a watershed that is associated with a certain number of monitoring sites with sediment contamination at levels likely to cause adverse effects.
The data also indicates that water quality standards in place for drinking water supplies in the Great Waters are not being exceeded for the pollutants of concern, but that surface water quality guidance and criteria are being exceeded for some of the Great Waters. In addition, nationally, fish consumption advisories were in place for 39 of 56 Great Waters waterbodies as of 1997.
Based on current trends, the EPA expects atmospheric deposition to remain a significant source of several pollutants of concern to the Great Waters for the foreseeable future. Because of the ability of these pollutants to persist and bioaccumulate, they are expected to remain in the water, sediments and biota for much longer.
The EPA says implementation of existing regulations is expected to further reduce emissions of mercury, NOx, POMs, dioxins and furans, cadmium, and hexachlorobenzene. The EPA expects pollutant emissions will be further controlled by several rules scheduled to take effect in coming years. As a result, atmospheric deposition and loadings of these pollutants may be significantly reduced, the report claims.
The report adds that actions taken to voluntarily reduce chemical use, implement pollution prevention initiatives, promote and develop alternative fuel vehicle and implement pollution control laws issued by US states and other nations will further reduce pollutant loadings to the Great Waters.
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