Exposure and Risk Asssessment Research

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Exposure assessment                                                         TOP

Exposure assessment involves describing the nature and size of the population exposed to a substance and the magnitude and duration of their exposure.  The evaluation could concern past or current exposures, or exposures anticipated in the future.

Exposure "pathways" describe the transmission and uptake of chemicals from the source to a human receptor or other target.  Pathways may include ingestion, inhalation and dermal contact.Urban and industrial areas can include many types of emission sources of air toxics. 

Refineries, like the one pictured at right, for example, emit a variety of gases and volatile organic compounds.

In this case, exposure assessments have focused on the inhalation pathway.

Vehicles represent the most common and a very important source of air toxics, especially for VOCs like benzene.  Commuter exposure to VOCs appear much higher than suggested by the use of fixed site monitors.  

See:  S. Batterman, J. Braun, C.Y. Peng, P. Warner, E. Butrym, “Exposure to Urban Air Toxics Exposures During Commuting:  A Field Study in the Motor City,” presented at 93rd Annual Meeting and Exhibit of the Air and Waste Management Association, Salt Lake City, Utah, June 18-22, 2000.

Modeling                                                                     TOP

Receptor modeling.  Currently, students are developing a receptor model for air toxics in Detroit, using approximately 10 years of data observed at several sites. This analysis will help to identify and quantify major contributing sources. 

Dispersion modeling and exposure assessment. Another application of an air quality model was used to estimate chemical exposures resulting from an enormous fire that released approximately 15,000 tons of SO2 at ground level in South Africa in 1995. 

The photo on the left shows the remnants of the sulfur stockpile after the fire. 

Some concentrations reached above 100 ppm, the IDLH (immediately dangerous to life and health) level, an unprecedented SO2 exposure to a general population.

This disaster killed and injured many individuals, and caused thousands to be evacuated.  It also caused reactive airways dysfunction syndrome (an asthma-like disease), the first association of this disease with SO2. 

Predicted SO2 concentrations (the 2nd highest hourly average in ppm) are displayed as isopleths over a 6 by 6 km area in the affected community.

See:  S. Batterman, N. White, “Exposures and Health Effects from a Large Sulfur Fire in South Africa,” presented at the Air and Waste Management Association Annual Meeting, St. Louis, MO, July, 1999.  

Also see: S. Batterman, E. Cairncross, Y-L Huang, “Estimation and Evaluation of Exposures from a Large Sulfur Fire in South Africa,” Environmental Research, Section, A, 81, 316-333, 1999.

Risk assessment                                                              TOP

What is chemical risk?

(1) The fraction of excess cases (mortality or morbidity) expected in a population for a period of exposure to a contaminant. 

(2) The probability of an adverse effect from a contaminant.

Special attention must be paid to vulnerable and/or highly exposed populations. 

What is risk assessment?

The process of determining the likelihood of short and long term adverse consequences to individuals or groups from the use of a particular technology in a particular area. It is also defined as the characterization of the potential adverse health effects of human exposures to environmental hazards. 

Risk assessments are performed to predict and analyze health and ecological impacts that may result from the use of a technology, agent or process. Health risk assessments evaluate the probability or severity of human injury, disease or death.

Often, we are concerned with the releases of toxic chemicals into air, water and soil. People may be exposed to these chemicals in food, drinking water, and house dust. 

Risk assessment may also address pathogens such as cryptosporidium in water and legionnella in air. Risk assessments provide vital information needed to manage these risks.

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Hazardous waste is an area that utilizes principles of risk assessment in both the remediation of contaminated sites, as well as evaluation of alternatives for the safe disposal.