Using existing levels of exposure, such as concentrations of a constituent of concern in the water column, sediments, or shellfish, one can determine the likelihood that an adverse effect will occur.

Characterize Exposure. Exposure characterization is the step in which the degree to which the critical elements of the ecosystem or humans are exposed to various sources of concern is determined. Exposure characterization can be very complex in the context of the coastal zone. The key factor to take into account when characterizing sources and exposure in the coastal zone is that environmental concentrations of a constituent of concern will vary considerably depending on where the source enters the system and how many different sources a particular constituent is associated with. For example, seepage from septic systems adjacent to a shallow and enclosed bay is likely to result in locally increased concentration of nutrients and, if sited inappropriately, pathogens. If the bay also receives stormwater runoff that contains significant concentrations of these contaminants, the problem would be compounded. It may also be difficult to determine the relative contributions of the two sources.

Characterizing exposures to humans can also be confounding because of the multitude of behavioral factors associated with human exposures. These are discussed further in the section below on human health risks.

Assessing Human Health Risks. The World Health Organization states that "health is a state of complete physical, mental and social well-being and is not merely the absence of disease or infirmity" (WHO 1948). Rene Dubos defined health as "expressions of the success or failure experienced by the organism in its efforts to respond adaptively to environmental challenges" (Dubos 1965). In the coastal urban environment, human health issues of concern include not only acute and chronic toxicity but also other contributors to human well-being, such as nutritional value of fish and shellfish stocks, recreational opportunities, and contributions of the coastal ecosystem to mental well-being. As an example of the latter type of effect, algal blooms or fish kills that diminish the recreational opportunities in the coastal area would create stress as well as economic consequences for those whose livelihood depends on recreation. While recognizing the full breadth of human health affected by damage to the coastal environment, the approach used here will focus on assessing risks for acute and chronic illnesses caused by exposure to hazardous chemicals and microbiological stressors. Within integrated coastal management, other stressors will be considered as part of other human expectations (such as economic value of a recreational resource) even though there may be direct or indirect health consequences.

Adverse human health effects can range from minor to severe to fatal, and are usually classified as either acute or chronic. Acute effects or illnesses occur with short-term exposures, are of short latency, and usually

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