Environmental contaminants and exposure

Introduction People come into contact with potentially hazardous chemical contaminants as part of daily life. Chemical contaminants arise from natural and anthropogenic sources. Chemical contaminants occur in the ambient environment such as outdoor air, surface water and soil, and in the air, dust on surfaces, food, water, and products found and used in indoor environments, e.g. workplaces, schools, and homes. Contact or exposure to a hazardous chemical contaminant is necessary but not sufficient in itself to result in an adverse health effect. A sufficient amount of the chemical contaminant must be absorbed into the body and must reach the relevant site within the body where it may change or disrupt normal function. Absorption (or uptake) is influenced by properties of the body and properties of the chemical contaminant. Once inside the body the contaminant may be altered by metabolism, stored, or eliminated as waste. This chapter reviews concepts of exposure and dose; identifies sources of contaminants; and describes the circumstances of human exposures. The range of contaminants of concern for reproductive health is discussed in Chapter 1. Selected examples highlighting exposure and dose topics are provided below. Understanding exposure and dose. Basic definitions of exposure and dose. The following definitions are adapted from Zartarian et al. Exposure is defined as contact between a contaminant and the target (for our purposes the target of interest is the human body). Dose is defined as the amount of contaminant that enters the target over a specified time period by crossing a contact boundary.