Challenges in Developing Human Health Indicators

Human health indicators provide important tools that regulatory agencies can use to identify environmental health problems, develop programs to reduce the problems, then gauge the success of those efforts. For example, the declining levels of lead in children's blood confirm that the nation's strategies to remove lead from gasoline, water, and paint have successfully reduced exposure to lead. Similarly, the decline in urinary cotinine levels confirms that efforts to reduce smoking have been successful in reducing exposures to ETS.

For many other pollutants, major knowledge gaps and challenges remain in linking environmental pollution to health problems. Sorting out the role of the environment, the role of other factors (e.g., genetic make-up, lifestyle choices such as diet and exercise), and the importance of their interactions remains an enormous scientific challenge. The time between exposure and the development or diagnosis of disease, as well as the problems of tracking a mobile population, further complicate the issue of clarifying connections between exposure and harm to health. An emerging area of science involves examining the possible combined (additive), synergistic, and cumulative effects of numerous pollutants in the environment. This field of study merits greater development. Finally, not all chemical exposures result in harm to health. With a better understanding of the contribution of environmental factors to the development of disease, EPA will be able to use established health outcome measures—disease trend and exposure data—to enhance environmental management efforts and to assess the effectiveness of those efforts.

Disease registries could be improved to provide valuable assistance in tracking many diseases. Currently, most disease indicators are based on mortality data, which have serious limitations for linking environmental exposures to disease. Data on the number of new cases (incidence) of a disease or the existing cases (prevalence) of a disease in a population can provide better information, but no comprehensive nationwide systems exist for collecting these data. For example, there is currently no national registry for birth defects. Also, it is nearly impossible to get an accurate national picture of the number of people affected by outbreaks of waterborne diseases. Occurrence of endemic waterborne disease is grossly underreported. Submission of waterborne disease information to CDC is strictly voluntary, and state-level data pose problems because the list of gastrointestinal diseases that must be reported varies by state. Also, for an outbreak to be detected, many people need to become ill at the same time, and many cases go unreported or are not diagnosed.

Better national-level disease data that could be linked directly with environmental monitoring data would support efforts to establish connections between disease and environmental exposures. For meaningful comparisons, all data sets should have similar timeframes (the same months or number of years) and locations. Also, national-level efforts would benefit from more data that can be sorted by several relevant factors, such as race (which can help in identifying disparities in health status and outcomes), income, occupation, and residence. Such data can be gathered only through better collaboration between and among environmental and health agencies at all levels, as well as hospitals, clinics, and medical offices. As EPA works to develop environmental indicators that reliably signal trends in exposures and disease, the Agency will also work to improve cooperation with the federal and state agencies that collect relevant information.

Appropriate indicators that address these challenges can help the agencies responsible for monitoring and managing the nation's health to flag and respond to potential problems, such as an upsurge in cases of an environmentally related disease or rising contaminant levels in human tissues. The same indicators might, ideally, show whether pollution control actions are actually reducing the number of people who develop diseases associated with environmental agents. This information will help EPA and other agencies to enhance priority-setting to best protect the health of the nation's people.