Diseases & Conditions
Learn about possible associations between environmental contaminants and select diseases and conditions.
The lower respiratory tract includes the trachea, bronchi, bronchioles, and lungs. Lung diseases include any condition that causes the lungs not to function properly. Asthma occurs when the airways (bronchi and bronchioles) swell, making it difficult to breathe (move air into and out of the lungs). Symptoms include wheezing, coughing, tightness in the chest, and difficulty breathing.
What triggers asthma varies from person to person but may include pollen, dust mites, mold spores, pet dander, or other indoor allergens. Outdoor air polluted with chemicals from vehicles, factories, and other sources may also trigger asthma and other lower respiratory tract diseases.
Emphysema occurs when the air sacs (alveoli) of the lungs are damaged, causing shortness of breath and reducing the amount of oxygen reaching the bloodstream. People with emphysema also tend to have chronic bronchitis, an inflammation of the bronchi, which often causes a persistent cough.
Emphysema and chronic bronchitis are two conditions that make up chronic obstructive pulmonary disease (COPD). Symptoms of COPD include breathing difficulty, cough, mucus (sputum) production, and wheezing. Causes include long-term exposure to irritating gases or particulate matter, often from cigarette smoke. Smoking is the leading cause of COPD. People with COPD have an increased risk of developing heart disease, lung cancer, and other conditions, but most can control their symptoms fairly well with proper treatment.
Other lower respiratory tract diseases include pneumonia and lung cancer. Pneumonia is an infection of the air sacs caused by bacteria, viruses, and fungi. Lung cancer is the uncontrolled growth of abnormal cells in one or both lungs, usually in the cells that line the air passages. The abnormal cells divide rapidly and form tumors.
Birth defects, or congenital malformations, are abnormalities present at birth. They are among the leading causes of mortality in the United States for infants and children under the age of five. Birth defects affect one in every 33 babies born in the United States each year. While birth defects can occur during any stage of pregnancy, most defects occur in the first three months of pregnancy when the organs are forming.
The abnormalities may be physical, functional, metabolic, or non-disabling. Physical defects include conditions such as oral cleft, spina bifida, congenital heart defects, and upper and lower limb reductions. Functional defects affect the cardiovascular system, nervous system, immune system, or endocrine system and may not be recognized until years after birth. Metabolic defects like Tay-Sachs disease affect body chemistry. Non-disabling defects may be unwanted and cosmetically disfiguring, but may not necessarily result in a disability.
Both genetic and environmental factors cause birth defects. Environmental factors include physical agents like radiation, pollutants, maternal drug use, and maternal illness or infection. In particular, exposure to ethanol in alcoholic beverages, solvents, and fuel is strongly associated with birth defects. Exposure to mercury can lead to birth defects and neurological disorders. Repeated exposure to toluene may also increase the risk of birth defects.
Cancer develops when genes mutate and change the way cells function, leading to abnormal cell growth and division. Most gene mutations occur after birth, while some are inherited. Environmental causes of gene mutations include radiation, viruses, and cancer-causing chemicals (carcinogens) such as asbestos, radon, and chemicals in firsthand or secondhand tobacco smoke. Other causes of gene mutations include obesity, hormones, chronic inflammation, and a lack of exercise.
An exposure to a carcinogen does not necessarily result in cancer. Other factors play a part, including the amount and duration of exposure and an individual’s genetic background. Every few years, the National Toxicology Program publishes a Report on Carcinogens that lists substances that are known or reasonably anticipated to cause cancer.
Cardiovascular (heart) disease is the leading cause of death in the United States and worldwide. It is the broad term for problems of the heart and blood vessels. These problems are often due to atherosclerosis, a hardening of the arteries caused by a buildup of fat, cholesterol, or other substances along the arterial walls. As these substances build up, the arteries narrow or clog, leading to problems throughout the body.
Individual health (physical fitness), lifestyle (diet), family history, and environmental exposure to pollutants are all factors contributing to a risk of cardiovascular disease. Environmental exposure to particulate air pollution, lead, tobacco smoke, and carbon monoxide may increase the risk of coronary heart disease and heart attacks. Factors contributing to that risk are the amount of pollution, the extent of exposure, and the overall health of the individual.
Learning disabilities are psychologically-based disorders. They include problems using written or spoken language, performing math, coordinating movements, and directing attention. Developmental disabilities broadly include any severe, chronic condition apparent by age 22 and causing functional limitations. Examples include problems with self-care, language, learning, mobility, self-direction, independent living, and economic self-sufficiency.
Some learning and developmental disabilities are known or suspected to have environmental factors as contributors. In general, exposures in an embryo, fetus, infant, and child are more likely to cause harm to the developing brain and nervous system than they are later in life. Toxicants associated with these disabilities include:
• Carbon disulfide
• Carbon monoxide
• Polychlorinated biphenyls (PCBs)
• Tobacco smoke
Reproductive health refers to all diseases and conditions affecting the male and female reproductive systems. Disorders include birth defects, developmental disorders, low birth weight, preterm birth, reduced fertility, and impotence.
Environmental exposure to pollutants is one of the greatest threats to reproductive health. For example, excessive exposure to lead has been linked to reduced fertility in men and women. Exposure to mercury can lead to birth defects and neurological disorders. Endocrine disruptors, chemicals that may interfere with human hormones, can affect fertility, pregnancy, and other aspects of reproduction.