Page 22 - AW MayJune 19

WORLD NEWS

Drinking California tap water could

increase risk of cancer

published by the state Office of Environmental Health
Hazard Assessment, or OEHHA, and the EPA’s Integrated
Risk Information System. The benchmarks are the levels that
scientists calculate pose a one-in-a-million risk of cancer
– the chance that one person out of a population of one
million will develop cancer if he or she drinks the water for
a 70-year lifetime.
Most U.S. drinking water systems meet all state and
federal legal limits. In California, 90 percent of systems met
all federal standards for the past seven years, according
to the state’s Safe Drinking Water Information System. But
legal doesn’t always mean safe.
Legal limits are based on economic and political
he array of toxic pollutants in California drinking water considerations that usually don’t reflect the lower levels
Tcould in combination cause more than 15,000 excess that scientists have found pose health risks. Indeed, over
cases of cancer, according to a peer-reviewed study by 85 percent of the cancer risk calculated in the EWG study
scientists at Environmental Working Group – the first such is due to contaminants that were below legal limits. Legal
study to assess the cumulative risk from carcinogenic limits may also be based on outdated science: No new
drinking water contaminants. contaminants have been added to the list of nationally
For an article published today in the journal regulated drinking water pollutants in two decades.
Environmental Health, EWG scientists analysed state and The study found:
federal data on carcinogens and other toxic contaminants • About 3.1 million Californians get their tap water
that were detected from 2011 to 2015 in more than 2,700 from 495 systems in which contaminants pose
California community water systems. a cumulative lifetime cancer risk greater than
They developed a groundbreaking method of one additional case per 1,000 people. In those
calculating the combined health impacts of multiple communities, typically small to medium size, an
contaminants in a single water supply. estimated 4,860 people could develop cancer from
EWG found that the greatest risks tended to be in small drinking their tap water.
to midsize communities, highlighting that these places • The largest group of Californians – about 28.5 million
are often the most in need of costly treatment systems – get their tap water from 1,177 systems in which
and other infrastructure to ensure safe drinking water. The contaminants pose a cancer risk of one per 1,000
greatest risks were from arsenic, byproducts of disinfectant to one per 10,000 people. In those communities, an
chemicals, and hexavalent chromium, or chromium-6, the estimated 10,427 cases of cancer could be due to
notorious “Erin Brockovich” chemical. contaminants tap water.
Drinking water rarely contains only one contaminant, • Statewide, nearly two-thirds of drinking water
yet regulators currently assess the health hazards of tap systems contained at least two cancer-causing
water pollutants one by one. This ignores the combined contaminants in excess of one-in-a-million risk levels.
effects of multiple pollutants, which is how people ingest AW
them in the real world. Regulators commonly use the
cumulative risk approach to assess the health impacts of
multiple air pollutants, but the EWG study is the first known
use of this method for drinking water contaminants.
The U.S. Environmental Protection Agency publishes a
cumulative risk assessment of carcinogenic air pollutants,
known as the National Air Toxics Assessment. The EPA
has also proposed evaluating some contaminants by
groups, such as volatile organic compounds to make the
regulatory process more efficient. EWG’s study builds on
these concepts to assess tap water contaminants.
For California water systems, EWG compared
contaminant levels to the cancer risk benchmarks

20 MAY/JUNE 2019 Asian Water