4.1.1.3 Exposure Assessment
Exposure assessment aims to examine the likelihood that focus pollutants in the
contaminated sites migrate and threaten sensitive receptors on the basis of hazard
identification. This involves defining the main exposure pathways and exposure
assessment models for soil and groundwater pollutants, determining the values of
model parameters, and calculating the exposure of sensitive populations to soil and
groundwater pollutants.
Exposure assessment focuses on the measurement, estimate or prediction of the
magnitude, frequency, duration and pathway of human body (or other organisms)
exposure to a chemical substance or physical factor, which serves as a quantitative
basis for risk assessment. It also includes discussion of the size, distribution,
activity status, and contact method of exposed populations (or organisms), as well
as discussion of the uncertainties in the above information. Exposure can be
measured directly, but more commonly is estimated using mathematical models that
integrate parameters for pollutant emissions, concentrations, transport and transformation trends. However, the methods vary for assessing past, current and future
exposures. Using appropriate models, the total exposure of different populations at
different times can be estimated based on pollutant concentrations and distribution
in the environmental media, population activity parameters and biometric data. In
cancer risk assessment, typically the lifetime exposure is calculated. The Guidelines
for Exposure Assessment published by the US EPA in 1992 expounded on the
general concepts, quantification approaches, data collection and development,
exposure estimation, uncertainty assessment, and exposure characterization
involved in exposure assessment.
Both exposure scenarios and exposure pathways are highlighted in exposure
assessment. Exposure scenarios mean the scenarios that pollutants in the contaminated sites migrate and contact populations via different routes under defined land
use patterns. In theory, exposure assessment describes pollution sources, exposure
pathways and receptors, as well as uncertainties in the assessment process.
Regardless of hazards, chemical pollutants will not cause health risks if there are no
exposure routes for them to contact receptors. Since risk is always associated with
exposure, risk assessment must first examine the exposure scenarios and exposure
pathways of hazardous chemicals. In view of this, exposure assessment consists of
three basic components: exposure scenario characterization, exposure pathway
identification and exposure quantification, specified as follows:
(1) Exposure scenario characterization: The characteristics of exposure scenarios
and exposed populations are assessed. The basic characteristics of exposure
scenarios include local climate (e.g. temperature and precipitation), meteorology (e.g. wind speed, wind direction), agricultural production (e.g. farmland,
woodland and grassland), hydrogeological conditions (e.g. soil types and
aquifer characteristics), and surface water. The characteristics of exposed
populations include locations subject to pollutants, population activities, and
potential sensitive receptors.
4.1 Health Risk Assessment of Typical Groundwater Contamination Sites
71
Exposure assessment aims to examine the likelihood that focus pollutants in the
contaminated sites migrate and threaten sensitive receptors on the basis of hazard
identification. This involves defining the main exposure pathways and exposure
assessment models for soil and groundwater pollutants, determining the values of
model parameters, and calculating the exposure of sensitive populations to soil and
groundwater pollutants.
Exposure assessment focuses on the measurement, estimate or prediction of the
magnitude, frequency, duration and pathway of human body (or other organisms)
exposure to a chemical substance or physical factor, which serves as a quantitative
basis for risk assessment. It also includes discussion of the size, distribution,
activity status, and contact method of exposed populations (or organisms), as well
as discussion of the uncertainties in the above information. Exposure can be
measured directly, but more commonly is estimated using mathematical models that
integrate parameters for pollutant emissions, concentrations, transport and transformation trends. However, the methods vary for assessing past, current and future
exposures. Using appropriate models, the total exposure of different populations at
different times can be estimated based on pollutant concentrations and distribution
in the environmental media, population activity parameters and biometric data. In
cancer risk assessment, typically the lifetime exposure is calculated. The Guidelines
for Exposure Assessment published by the US EPA in 1992 expounded on the
general concepts, quantification approaches, data collection and development,
exposure estimation, uncertainty assessment, and exposure characterization
involved in exposure assessment.
Both exposure scenarios and exposure pathways are highlighted in exposure
assessment. Exposure scenarios mean the scenarios that pollutants in the contaminated sites migrate and contact populations via different routes under defined land
use patterns. In theory, exposure assessment describes pollution sources, exposure
pathways and receptors, as well as uncertainties in the assessment process.
Regardless of hazards, chemical pollutants will not cause health risks if there are no
exposure routes for them to contact receptors. Since risk is always associated with
exposure, risk assessment must first examine the exposure scenarios and exposure
pathways of hazardous chemicals. In view of this, exposure assessment consists of
three basic components: exposure scenario characterization, exposure pathway
identification and exposure quantification, specified as follows:
(1) Exposure scenario characterization: The characteristics of exposure scenarios
and exposed populations are assessed. The basic characteristics of exposure
scenarios include local climate (e.g. temperature and precipitation), meteorology (e.g. wind speed, wind direction), agricultural production (e.g. farmland,
woodland and grassland), hydrogeological conditions (e.g. soil types and
aquifer characteristics), and surface water. The characteristics of exposed
populations include locations subject to pollutants, population activities, and
potential sensitive receptors.
4.1 Health Risk Assessment of Typical Groundwater Contamination Sites
71