An environmental health hazard is a substance that has the ability to cause an adverse health event. This includes physical, chemical, and biological factors that are external to a person. Hazards can be natural or manmade.

Examples include:

• Air, water, and soil pollution from transportation, agriculture, industry, and other sources such as:
• Chemicals
• Toxic waste
• Radiation
• Disease-causing microorganisms and plants
• Pesticides
• Heavy metals
• Climate
• Extreme temperatures and weather events
• Where you live – home and community design
• Chemicals in consumer products

Health effects from the environment can be both short term (acute) and long term (chronic). Science has proven some links between health conditions and the environment. For example, it is known that poor air quality can trigger asthma, and that elevated blood lead levels in children can cause developmental disabilities. Scientists know that vulnerable populations such as the elderly and infants are most at risk to heat-related illnesses during heat waves, and that extreme weather can cause power outages that can lead to cases of carbon monoxide poisoning.

However, many links are suspected but not yet proven—environmental health is a complicated area of study and there are gaps in information about how the environment affects chronic diseases. Health problems with suspected links to environmental issues include:

• Certain cancers (i.e., bladder, liver)
• Asthma and other respiratory diseases
• Neurological (related to the nervous system) diseases
• Parkinson’s disease, multiple sclerosis, Alzheimer’s disease
• Developmental disabilities, such as cerebral palsy, autism, etc.