News outlets have spent years covering carcinogens, claiming that everything from
oral sex to
soup will cause cancer. What doesn’t get touched on as often are the
different classifications of carcinogens, leaving some people confused
at the difference between a “probable” carcinogen and a “possible”
The International Agency for Research on Cancer (IARC) is an intergovernmental
agency and forms part of the World Health Organization (WHO) of the United
Nations. Last updated in 2015, it is the most widely used system for classifying
carcinogens, and has evaluated the carcinogenic potential of more than
900 likely substances, placing them into one of five groups:
Group 1: Definitely carcinogenic to humans. Some examples include arsenic, asbestos,
Hepatitis B, Hepatitis C, Plutonium, processed meat, and Ultraviolet Radiation.
Group 2A: Probably carcinogenic to humans. There isn’t enough evidence to
definitively conclude that these substances cause cancer, but there’s
enough to warrant the warning label. Some examples include anabolic steroids,
diethyl sulfate (used to manufacture dyes and textiles), glyphosate (brought
to market by Monsanto as “Roundup”), phenacetin (a pain-relieving
and fever-reducing drug), and trichloroethylene (a volatile anesthetic).
Group 2B: Possibly carcinogenic to humans. There isn’t enough evidence to
place it in Group 2A, but there’s enough to warrant the warning
label. Some examples include chloroform, lead, naphthalene (the main ingredient
in traditional mothballs), phenytoin (also known as Dilantin), and titanium
dioxide (used in everything from sunscreen to paint).
Group 3: Cannot be classified as a carcinogen. There isn’t enough evidence
to place it in a higher group, but there’s just enough evidence
to keep it out of Group 4. Some examples include caffeine, cholesterol,
fluorides, hydrogen peroxide, and talc.
Group 4: Probably doesn’t cause cancer. Evidence could change the classification
of a substance in Group 4, but the evidence suggests that exposure to
these substances will not cause cancer. The only substance in this group
is caprolactam (the precursor to Nylon 6, a widely used synthetic polymer).
The American Cancer Society uses information from the IARC as well as the
U.S. National Toxicology Program (NTP) to compile their
list of probable and known carcinogens. Unlike the IARC, the NTP only classifies carcinogens in two groups. Its
list was last updated in 2011.
Known to be a human carcinogen. This group is noticeably smaller than the IARC’s Group A, but contains
many of the same substances.
Reasonably anticipated to be a human carcinogen. This group is comparable in size to the IARC’s and contains many
of the same substances, but doesn’t include some notable substances
like glyphosate (Roundup).
If you have been diagnosed with cancer after being exposed to a potentially
carcinogenic substance and are in need of legal counsel, our lawyers at
Domina Law Group have been representing victims in Nebraska since 1982.
Contact us today for a case evaluation.