The Science

Environmental and occupational contributors to cancer

The science is clear: dozens of chemicals found in indoor and outdoor environments contribute to cancer. This evidence is based on comprehensive reviews by authoritative scientific bodies, including the World Health Organization’s International Agency for Research on Cancer (IARC) and the U.S. National Toxicology Program (NTP).

Cancer develops from a combination of genetic and external risk factors, a series of interactions, much like electric circuitry, where many components need to be in place to cause a light to turn on. In the case of environmental chemicals, exposure to any one pollutant may pose only a small increased risk of cancer in an individual, but if exposures to that pollutant are widespread and occur in most people, even small increases in individual risk can result in significant numbers of cases in the general population. In addition, when many people are exposed to multiple substances that increase cancer risk to varying degrees in various ways, that too can result in significant numbers of cases in the population. The more a population is exposed, the greater the number of cases of cancer that can be prevented by reducing those exposures.

A Science Companion document produced by the Network reviews the state of the science related to the contribution of environmental and occupational chemicals to cancer, with a specific focus on risk factors that are elevated in Southwestern Pennsylvania. Environmental chemicals and pollutants of particular concern in our region are priority environmental risk factors.

CENSWPA issues a monthly Digest each month, which includes a list of research articles published the prior month.  Each year, the Science foundational team of CENSWPA reflects on the collection of articles. The 2023 Year in Review – A Research Brief revealed the following as noteworthy:

  • Two significant studies conducted in Pennsylvania add to the growing literature about impacts on cancer survival associated with air pollution exposure and increased cancer risks associated with the fracking industry.  
  • As CENSWPA observed in the 2022 literature, research continues to demonstrate increased risk of childhood cancers associated with exposure to pesticides and air pollution.
  • Additionally, CENSWPA observed in the 2021 literature, a range of cancers beyond lung cancer show increased risk associated with exposure to air pollution. 
  • With our nation now having a sharp focus on environmental injustices, new research sees clear links with increased risks of cancer.

Priority environmental risk factors

These environmental chemicals contribute to cancer risk in Southwestern Pennsylvania. Assessment of exposure–an important component of risk–is limited for some of these risk factors; for others, we know that exposure is higher in our region than elsewhere. Reducing exposure to chemicals or pollutants known to contribute to cancer is an important and often overlooked strategy for cancer prevention.

Allegheny ranks among the worst 4% of counties nationwide with regard to estimated cancer risk from exposure to hazardous air pollutants (HAPs) and Diesel Particulate Matter (DPM). This does not include the cancer risk from fine particulate matter.

Carcinogens released and formed during the process of fracking natural gas include benzene, formaldehyde, particulate matter, and radioactive compounds threaten the wellbeing of residents in a number of counties in SWPA. Studies have shown that children living closer to oil and gas wells have higher rates of leukemia.

Some chemicals used in agriculture, in homes and gardens, on golf courses, playing fields, parks and in buildings are known carcinogens; others disturb biological processes that normally project against cancer. Early life exposures to pesticides used at home are tied to leukemia and brain tumors in children, as are parental exposures. A recent review of 40 studies concluded that documented use of pesticides was associated with brain cancers in farmers.

Pennsylvania ranks third among all states for levels of radon–roughly 40% of homes have radon above EPA’s action levels. Radon is the second leading cause of lung cancer in the US.

Chemicals known to cause cancer are in a range of consumer products, including cosmetics, furniture, building materials, and home and garden pest control products, despite availability of safer alternatives.

Drinking water in our region has been contaminated by radioactive and other hazardous substances, including from fracking activities.