Chapter Summary

Health is a state of physical, mental, and social well-being, not merely the absence of disease or infirmity. Nearly every human disease probably has some connection to environmental factors. For most people in the world, the greatest health threat in the environment is still, as it always has been, from pathogenic organisms. Although diseases of affluence and old age now are the leading causes of death worldwide, bacteria, viruses, and other infectious agents still kill millions of people each year, and cause immense suffering and economic losses. Highly lethal emergent diseases, such as Ebola and AIDS, along with new drug-resistant forms of old diseases, are an increasing worry everywhere in the world. Some of these extremely virulent new pathogens could be used as bioweapons, and might represent the greatest risks for terrorist attacks.

Hazardous and toxic materials are serious health threats nearly everywhere. Allergens, mutagens, and carcinogens represent some of the chronic effects of persistent organic pollutants. The most notorious “dirty dozen” POPs have been banned, but new ones, including PBDE, CCA, and PFOs have recently been widely discovered.

The distribution and fate of materials in the environment depend on their physical characteristics and the processes that transport, alter, destroy, or immobilize them. Uptake of toxins into organisms can result in accumulation in tissues and transfer from one organism to another.

Estimating the potential health risk from exposure to specific environmental factors is difficult because information on the precise dose, length and method of exposure, and possible interactions between the chemical in question and other potential toxins to which the population may have been exposed is often lacking. In addition, individuals have different levels of sensitivity and response to a particular toxin and are further affected by general health condition, age, and sex.

Estimates of health risks for large, diverse populations exposed to very low doses of extremely toxic materials are inexact because of biological variation, experimental error, and the necessity of extrapolating from results with small numbers of laboratory animals. In the end, we are left with unanswered questions. Which are the most dangerous environmental factors that we face? How can we evaluate the hazards of all the natural and synthetic chemicals that now exist? What risks are acceptable? We have not yet solved these problems or answered all the questions raised in this chapter, but these issues need to be discussed and considered seriously.