According to the National Institute of Environmental Health Sciences (NIEHS), human health and human disease result from three interactive elements - environmental factors, individual susceptibility, and age. 

Environmental medicine is the healthcare specialty concerned with human illnesses or dysfunctions that result from environmental factors. Environmental medicine specialists participate in a wide range of activities in their quest for answers regarding how the environment affects our health.

For example, among many other topics, the NIEHS is currently studying cancers, breast, and testicular; lead poisoning; birth and developmental defects; agricultural pollution; neurologic disorders; sterility; and ways to replace animals as subjects in research.

Environmental medicine departments or programs are found in large medical centers throughout the US. Some of the many services they offer include local, state, or national disease-prevention programs; epidemiological studies and research; distribution of standards, guidelines, and recommendations; and partnering with other organizations, such as health departments and environmental agencies, to help prevent environmental disease.