Exposure to Environmental Contaminants

Human exposure to environmental contaminants can be measured in the ambient environment (air, water, land), at the point of human contact, or after contaminants have entered the human body through entry portals such as the eyes, skin, stomach, intestines, or lungs.
 

Different approaches are used to measure or estimate exposure, each with advantages and disadvantages. These approaches include ambient concentration measurements, exposure modeling, personal monitoring, and biomonitoring.

• Ambient concentrations: Measurement of ambient concentrations provides information about how much of a contaminant is present in the environment (air, water, or soil), but not how much of the contaminant humans actually come in contact with. In some cases, ambient concentrations may be modeled or estimated rather than measured.
  
  This type of exposure estimate has provided a valuable foundation for many of the regulatory and non-regulatory actions that have been taken to limit exposure to ambient contaminants. Measurements of ambient concentrations of contaminants are presented in Air, Water, and Land indicators, but cannot be directly linked with the biomonitoring indicators presented to address the ROE exposure question.
   
• Exposure modeling: Exposure models estimate exposure by combining information about environmental contaminant concentrations with information about people's activities and locations (e.g., time spent working, exercising outdoors, sleeping, shopping) to account for the contact with contaminants. This approach requires data on contaminant levels where people live, work, and play, as well as knowledge of their day-to-day activities.
   
• Personal monitoring: With personal monitoring, an individual wears a monitoring device during normal day-to-day activities. Personal monitoring provides valuable insights into the source of contaminants to which people are being exposed. It is most commonly used in workplaces.
  
  A challenge with personal monitoring (as with biomonitoring) is ensuring that the extent of sampling is sufficient to be representative of the population being studied. No national-scale personal monitoring data are available.
   
• Biomonitoring: Biomonitoring measures how much of a contaminant—or its metabolite(s) or reaction product(s), referred to as “biomarkers”—are present in the human body. Measurements are most commonly made in blood or urine, but can also be taken from a variety of other body compartments, such as feces, breast milk, hair, nails, and exhaled air, as well as tissues obtained through biopsy or autopsy.
  
  Several environmental contaminants, including heavy metals, some pesticides, and other persistent organic pollutants, can accumulate in the body. Biomonitoring has been used to characterize exposure to lead and some other metals for a number of years. More recently, advances in biomonitoring have enabled measurement of many other environmental contaminants.