Human Health: Other issues -- Contaminated soils and sediments

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Other issues in the Great Lakes

Other health issues
in the Great Lakes
Apart from the major Great Lakes health concerns of drinking water, recreational water, and fish consumption, there are a number of related issues that are interconnected to air and water quality, pollution and contamination, agriculture and industry, and wildlife.

Contaminated soils and sediments
Just as soils are the ultimate fate of persistent chemicals in the air, sediments are a sink for chemicals in aquatic systems. While plants grow in soils and form the base of the terrestrial food chain, benthic organisms that live in sediments, lacking cell walls, and containing high proportions of lipids and fats in cell membranes and other organelles, are the base of the aquatic food chain. Thus, sediments are not merely a sink for hazardous compounds, but also a source of lipophilic compounds to the aquatic food chain and, potentially, to humans and other fish eaters.

It has become clear that the accumulation into the food chain of persistent bioaccumulative toxic (PBT) chemicals, such as PCBs, dioxins and furans, and mercury (as methylmercury), is not solely dependent on their concentration in sediments. Characteristics of the sediment such as organic content, microbial environment, pH, redox conditions, and presence of sulfates and sulfides can all affect the potential for PBT chemicals to be bioaccumulated. Furthermore, sediment reactions are typically characterized and studied as static systems.

In the environment, however, reactions which occur may be affected by groundwater flow. Groundwater flow may cause water of groundwater or surface water origin to regularly replace porewater. Therefore, equilibriums between reactants and products may not be achieved, and production and/or transport of some compounds might occur at much higher rates than previously proposed. Without a better understanding of the chemical reactions and interactions in this transition zone between groundwater and surface water, quantitative risk assessment of the potential effects of PBT contaminated sediments will remain associated with large uncertainties.

There are numerous hazardous chemicals which have greater health impacts on ecological communities than humans when found at elevated levels in sediments. These include some metals, lead for example, and some organic compounds, such as PAHs.

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