Site Title Goes Here

Shortcut Navigation:

Vinyl Chloride


Janet Gray, Ph.D.
Janet Gray, Ph.D.

As author of our 2008 and 2010 State of the Evidence reports, Dr. Gray drives the science behind all our work.

Printer Friendly

Air & Water Exposures

Nothing's more fundamental to life than air and water. Unfortunately, both air and water can contain chemicals that are harmful to us.

When it comes to the air we breathe, it's not just our lungs that are in danger. Air pollutants account for 35 of the 216 chemicals associated with increases in mammary gland tumors in animals. There is widespread exposure to many of these chemicals in the air we breathe outside, as well as in our offices, homes, restaurants and schools.

Although that sounds scary, it's important to note that most of the air pollutants are from just a few sources: primary and secondhand tobacco smoke, diesel exhaust and specific occupational exposures.

Chemicals related to breast cancer also make their way into lakes, streams and groundwater systems. Of particular concern are pesticides from agricultural and home use, dioxins and pharmaceutical hormones that make their way down household drains.

Hydraulic Fracturing (fracking)

Hydraulic fracturing, commonly referred to as fracking, is a process used to increase production in oil and natural gas wells. More recently, fracking has been used in combination with horizontal drilling through shale layers to reach natural gas reserves that were previously not easily accessed. Large quantities of water and other fluids are pumped into the ground at high pressure, which causes rock to break and allows gas to be extracted. Fracking fluids can contain chemicals linked to breast cancer, including known and suspected carcinogens such as benzene and toluene, and endocrine-disrupting compounds such as the phthalate DEHP. Evidence is beginning to emerge that these chemicals may contaminate underground water sources. Researchers have also found that ground and surface water near fracking sites has more endocrine disrupting activity than water from other locations. In addition, waste water containing fracking fluids, bromine salts (which interfere with wastewater treatment), minerals and radioactivity from deep in the earth flows back out of wells and must be stored and disposed of safely. There have been a number of spills of fracking waste water, and underground storage of this waste has been implicated in the increased incidence of earthquakes around some storage wells. A summary of the chemicals used in fracking can be found here.


Dioxin is formed when chlorine breaks down, and can be found in both water and air. Dioxins are known human carcinogens and endocrine disruptors. One dioxin has been classified by the International Agency for Research on Cancer (IARC) and the Environmental Protection Agency (EPA) as a known human carcinogen.

Endocrine Disruptors from Wastewater

Small amounts of hormones from medications like hormone-replacement therapy and oral contraceptives can make their way from people's bodies into municipal wastewater systems. Similarly, hormone-disrupting compounds from personal care products also go down household drains. These chemicals are not fully removed during water treatment processes, and end up in household tap water and water used to irrigate lawns and gardens.

Organic Solvents

Organic solvents are a class of chemicals that includes chlorinated and other solvents, including toluene, methylene chloride, trichloroethylene and formaldehyde. Sources of exposure include outdoor and indoor air pollution, waste incineration, cleaning products and some cosmetics. They are also used in the manufacture of computer parts.


Many pesticides, including herbicides and other pest-killing poisons, have been labeled as human or animal carcinogens. A 2006 report demonstrated that lifetime use of residential pesticides may be associated with an increase in risk for breast cancer. Studies have found that many of these chemicals are present in water supplies, as well as in samples of air and dust from homes.


DDT was widely used in the United States as a pesticide in agriculture and insect control until it was banned in 1972. DDT and its breakdown product, DDE, persist in the environment, in the food chain and in the human body. The main source of human exposure is through consumption of meat, fish and dairy products. The pesticide is still used in some countries to control mosquitoes. Recent studies show that women exposed to DDT during childhood and early adolescence have an increased risk of developing breast cancer.


1,3-butadiene is an air pollutant created by internal combustion engines and petroleum refineries. It is also used in the manufacture and processing of synthetic rubber products and some fungicides, and it is found in tobacco smoke. The EPA found that it is carcinogenic to humans, with the main route of exposure being inhalation.

Aromatic Amines

Aromatic amines are a class of chemicals found in the plastic and chemical industries, and they are found in environmental pollution such as diesel exhaust and tobacco smoke. One aromatic amine is known to cause mammary tumors in rodents. They can also have direct effects on cell division, which may enhance the development of tumors.

Vinyl Chloride

Vinyl chloride may be released into the air or wastewater when polyvinyl chloride (PVC) is made. Vinyl chloride has also been found in the air near hazardous waste sites and landfills and in tobacco smoke. Vinyl chloride was one of the first chemicals designated as a known human carcinogen by the National Toxicology Program (NTP). It has also been linked to increased mortality from breast cancer among workers involved in its manufacture.

Polycyclic Aromatic Hydrocarbons (PAHs)

Polycyclic aromatic hydrocarbons (PAHs) are byproducts of combustion, from sources as varied as coal burners, diesel engines, grilled meats and cigarettes. PAH residues are often found in the air and in house dust. Exposure is primarily through inhalation. They have been shown to increase risk for breast cancer.

Light at Night (LAN)

Exposure to light-at-night (LAN), such as that experienced by night-shift workers and flight attendants, lowers levels of melatonin, a hormone that appears to have anti-cancer properties. Research suggests a link between night-shift work and increased risk of breast cancer, possibly through this melatonin-LAN pathway.

Non-ionizing Radiation


What can you do personally to protect yourself from toxic exposures in air and water?

Tips for protecting yourself and your environment >

Electromagnetic waves are a type of non-ionizing radiation. They are produced by cell phones, wireless networking, radio towers, computers and electric lighting. The International Agency for Research on Cancer (IARC) has classified electromagnetic fields as possible human carcinogens; but consensus has been difficult to reach.

Tobacco Smoke

Tobacco smoke contains polycyclic aromatic hydrocarbons (PAHs), which may explain a potential link between increased breast cancer risk and both active and passive smoke inhalation. Tobacco smoke contains hundreds of other chemicals, including three known human carcinogens. A recent study found that both active and passive smoke inhalation increase the risk of breast cancer in premenopausal women.


Benzene is one of the highest volume petrochemical solvents currently in production, and global production rates are expected to continue to grow. It has been designated as a known human carcinogen. Exposure comes from inhaling gas fumes, automobile exhaust and tobacco smoke. Benzene poses a serious hazard for people exposed through manufacturing and refining industries.

Polychlorinated Biphenyls (PCBs)

Polychlorinated biphenyls (PCBs) have been banned since 1976, but as many as two-thirds of all insulation fluids, plastics, adhesives, paper, inks, paints and other products containing PCB manufactured before the ban remain in daily use. One type of PCB acts like an estrogen; a second, like an anti-estrogen; and a third appears not to be hormonally active. Therefore, most studies look at total PCB levels.