Human Exposure and Health Risk

Featured Study: Ozone Exposure in the Eastern USA

Exposure analysis and visualization of spatiotemporal pollutants in relation to their health effects are both important challenges for environmental health scientists and assessment modelers. In the context of human exposure and integrated risk assessment, this has been one of the first space-time studies to propose a horizontal integration among related sciences.

Our analysis led to informative spatiotemporal maps of ozone exposure and effect distributions. Additional results include an integrative analysis of the whole risk case in terms of human health burden.

About the Analysis

The following animation shows a series of maps for 4 consecutive days in the northeastern USA in July 1999. The maps on the left hand side illustrate the predicted human exposure to tropospheric ozone by analyzing records of pollutant concentration observations. Values range from 0 ppm (deep blue) to 45 ppm (red). The maps on the right hand side project the expected health effects as a normalized health damage indicator for the corresponding days. Indicator values range from 0 (white) to 10 (dark brown). 

For this study we employed a methodological framework to integrate the functional relationships between composite space-time ozone maps, pollutokinetic models of burden on target organs and tissues, and health effects. Within our proposed framework, we assembled a variety of knowledge bases (models and observations) from several relevant sciences. The goal is to embrace a working perspective that offers a meaningful physical interpretation of the exposure and biological processes that affect human exposure.

On the analytical front, we expressed natural uncertainties and biological variations in terms of spatiotemporal random fields. This representation leads to a rigorous examination, and deeper understanding in the development of improved models of spatiotemporal human exposure analysis and visualization.

In accordance to this sequence, our analysis started with prediction of exposure distributions from observed ozone values from stations across the region over the study period. The predicted distributions produced the input to pollutokinetic (or toxicokinetic) laws. These laws are linked to health effect models that describe how effects are distributed across populations. The health effect models might involve parameters to examine in more detail the health damage for specific population cohorts, and to produce suitable indicators for further analysis. An instance of such an indicator is illustrated in the above figure.

With this study we introduced a gateway to a holistic examination of the human exposure problem. The generality of this framework enables its application to a variety of other pollutants and types of problems.

Reference

Christakos G., and A. Kolovos. 1999. A Study Of The Spatiotemporal Health Impacts of Ozone Exposure. J of Exposure Anal and Envir Epidem, 9(4), pp.322-335.