Chemicals can be released into the soil, water or air from spilled or leaking containers, leaking landfills or dumps, through spraying, or released from smokestacks. These chemicals follow a pathway, or a route from the time of release to the point of human contact. When a substance enters the ecosystem where it is not normally found, it is called a contaminant. Humans become exposed to these contaminants by touching, breathing, or ingesting substances that contain the chemical (ATSDR, 1993).
To determine if human health is at risk of disease from contaminants, two things must occur: there must be an exposure to a contaminant; and the contaminant must be toxic. A complete exposure pathway must be present for disease to occur. The elements of an exposure pathway are:
- The source – how the contaminant got into the environment
- The transport media – how the contaminant moves through the environment
- The exposure point – how people came in contact with the contaminant
- The exposure route – how the contaminant entered the body
The receptor population – how susceptible the population is to the contaminant (adapted from ATSDR, 1994).
Additionally, whether the exposure causes disease depends on the dose (how much), the duration (how long you are exposed), the route of exposure (breathing, eating, or through the skin), other chemicals to which you are exposed, and individual characteristics such as age, sex, nutritional status, genetic traits, lifestyle and general health condition (ATSDR, 1993).
Dermal contact with contaminants in water, soil, air, food, and other media, such as exposed wastes or other contaminated material.
External exposure to radiation
- Microwave radiation – telecommunications and heating food
- Infrared radiation – infrared lamps to keep food warm in restaurants
- Radio waves
- High-Power RF – aircraft radar
There are three main kinds of ionizing radiation:
- Alpha particles, which include two protons and two neutrons
- Beta particles, which are essentially electrons
- Gamma rays and x-rays, which are pure energy (photons).
Ingestion of contaminants in groundwater, surface water, soil, and food.
Food from gardens
Inhalation of contaminants in air (dust, vapor, gases), including those volatilized or otherwise emitted from groundwater, surface water, and soil.
For more information see: ATSDR – PHA Guidance Manual – Chapter 6: Exposure Evaluation: Evaluating Exposure Pathways