Paul Lioy

Exposure Science Research Design

This chapter provides information on different study designs used to collect personal and microenvironmental measurements of exposure and to obtain distributions of exposure. The importance of biological monitoring in measuring internal exposure is discussed as part of the source to dose continuum. The major difference between the data collected to calculate exposure and data collected for environmental quality is examined for effectiveness in estimating exposures. These include the need for information on behavior and activities to assess the relative importance of various routes that lead to human contacts of contaminants. Methodologies are outlined for developing and using questionnaires, and for personal samplers for measuring inhalation, dermal, and ingestion exposure.

Exposure Science Applications: Within Environmental Health Sciences

This chapter briefly discusses the application of exposure science to different fields and particular areas within environmental health sciences. Some of the factors that influence a successful application of models within a field are described for human exposure estimation. These include incorporation of confounding factors and stressors along with exposure in epidemiologic studies. There are specific examples of exposure science application taken from the attack on the World Trade Center, utilization of GPS, GIS, and sensors to assess exposure, and drinking water exposures. The chapter ends with a brief examination of the potential role of the exposome concepts within the overall field of exposure science.

Exposure Routes and Types of Exposure

The concepts of total exposure are outlined in this chapter. There is a section that describes and provides examples for the individual routes of human exposure: ingestion, inhalation, and dermal contact. The concepts of multiroute, aggregate, cumulative, and multiagent exposures are explained, and their role in determining total exposure and associated risk are described for the reader. The importance of exposure science being receptor based rather than source based concept is illustrated for the reader. Further, the chapter discusses how to use collected data to provide estimates of exposure for hazardous waste sites. Included is the need to provide distributions of exposure rather than just point estimates of exposure to conduct risk assessments and examine risk management strategies.

Chapter 6 – Source to Exposure to Dose Modeling

The chapter provides basic information on requirements to estimate human exposure using exposure models along with the types of data needed to reduce model uncertainty. The steps required to model exposure are outlined in one section of the chapter. Differences are described that separate the results obtained using fate and transport versus exposure models. The application of two examples of important modeling tools: Stochastic Human Exposure and Dose Simulation (SHEDS) and the Modeling Environment for Total Risk (MENTOR) is illustrated in one section. New approaches are described for generating input variables for exposure models based on computational fluid dynamics, geographic information systems (GIS) and global positioning system (GPS).

History and Foundations of Exposure Science

The chapter includes a discussion of the origin and development of the field exposure science. Included are examples of the initial qualitative observations made by physicians. We then discuss developments through to the more complex relationships observed because of regulations and modern sources. The role of exposure science as a bridge in the source to dose to effects continuum is presented and an updated continuum is provided for the reader. There is a discussion of the influence of regulations on which measurements are made to directly infer exposures or estimate environmental quality. The difference between environmental monitoring and exposure characterization is elucidated as an important aspect of modern environmental health science. A discussion is presented on the importance of exposure science in risk assessment calculations.

Exposure Science Applications and Uses

The chapter discusses the way exposure science is used in applications associated with environmental science, the law, emissions from outdoor and commercial sources, and from personal and home products. These are necessary in order to determine potential adverse health effects from toxic contaminants present in environmental and occupational settings, and associated with various human behaviors and activities. The importance of a person’s proximity to small sources and the intensity of exposure are illustrated and compared to traditional concerns associated with industrial and mobile source emissions. Special emphasis is provided on the role of contaminants in personal and consumer products and emissions indoors on total exposure. The role of exposure science in legal issues is established for the reader.