The strong-smelling chemical formaldehyde causes cancer, while styrene, a second industrial chemical that's used worldwide in the manufacture of fiberglass and food containers, may cause cancer, the National Institutes of Health says.
The NIH said Friday that people with higher measures of exposure to formaldehyde are at increased risk for certain types of rare cancers, including those affecting the upper part of the throat behind the nose.
The chemical is widely used to make resins for household items, including paper product coatings, plastics and textile finishes. It also is commonly used as a preservative in medical laboratories, mortuaries and consumer products including some hair straightening products.
The government says styrene is a component of tobacco smoke, and NIH says the greatest exposure to the chemical is through cigarette smoking.
The two chemicals were among eight added to the government's list submitted to Congress of chemicals and biological agents that may put people at increased risk of for cancer.
Also on the list as a known carcinogen is a botanical agent called aristolochic acids, shown to cause high rates of bladder or upper urinary tract cancer in people with kidney or renal disease.
A warning issued a decade ago by the U.S. Food and Drug Administration advised consumers to discontinue using botanical products containing aristolochic acids. They are still available on the Internet and abroad and may be a contaminant in herbal products for treating symptoms for arthritis, gout, and inflammation.
Carcinogens do not always cause cancer. That depends on length and type of exposure and a person's genetic makeup. The American Cancer Society estimates that only about 6 percent of cancers are related to environmental causes and most of that is on-the-job occupational exposure.