On January 24 the Inverness Public Utility District
mailed its clients a notice explaining that the water system had exceeded
mandated levels for trihalomethanes (THMs), a cancer-causing byproduct
of chlorine. Bolinas residents were similarly warned on December 9 that,
in addition to THMs, their water had also failed to meet standards for
haloacetic acids, a similar byproduct. This was followed on February
17 with another notice of continued violations for haloacetic acids.
Even though both systems barely exceeded the allowable
amounts, they are required by law to alert their customers so long as
the problem remains.
The notices that were sent out explain that long-term,
elevated exposure to chlorine byproducts can lead to increased risks
of cancer, but at current levels present no immediate threat.
Chlorine? In Inverness?
"It surprises me. I didn’t know Inverness
used chlorine — I don’t think of it as having treated water,"
said Inverness resident Charlotte Brody. So she was doubly surprised
to discover that the Inverness Public Utility District was in violation
of federal drinking water standards for the carcinogenic chlorine byproducts.
Brody, who is executive director of Commonweal, a
group that studies environmental links to sickness, said she hadn’t
heard about the notice, but was worried about what it might imply. "It's
a very big deal to have too much exposure to these chemicals," Brody
said, "THMs are probable human carcinogens, not possible human
carcinogens. They’re classified as very serious chemicals."
When chlorine interacts with organic matter —
dirt and sediment — in the water supply, the reaction produces
a family of chemicals known generally as disinfection byproducts, amongst
them trihalomethanes and haloacetic acids.
These byproducts are not generally a problem for water
drawn from wells, where natural filtration removes organic material.
But the water in Inverness and Bolinas comes mostly from surface-level
sources which do contain organic matter, even after filtration at the
treatment plant. Because surface-water sources are open to the elements,
heavy rains produce a spike in both organic matter and the chlorine
byproducts that result.
If notices of water quality violations are only now
showing up in mailboxes, it’s because new stricter federal standards
only took effect in 2005, and difficulties with compliance only arrived
with the rainy winter weather.
Carcinogens?
Knowledge of the potential health risks of chlorine
byproducts dates back to the early 1970s. The EPA implemented an interim
standard in 1979 and, in 1998, announced the standards that are just
now resulting in the violations in Bolinas and Inverness.
According to a 2003 report from the National Resource
Defense Council, "more than a dozen epidemiological studies of
people who drank water containing chlorination by-products have linked
the chemicals to bladder cancer, and several studies indicate likely
links to colorectal, pancreatic, and other cancers." There are
also studies pointing to increased risk of early-term and low-weight
births, even miscarriage and birth-defects.
It is difficult, however, to determine at what point
exposure to disinfectant byproducts becomes a problem.
According to IPUD water system superintendent Jim
Fox, "there are a host of things that are potentially much more
harmful than going over the TTHM level." As for the actual health
risks, Fox defers to the state department of health. "The fact
that they say you don’t need to not drink the water… gives
you an idea of what they think the risk is."
Jennifer Blackman, general manager of the Bolinas
Public Utility District, said that there had not been many public inquiries
in response to the notice. Blackman encouraged concerned callers to
look beyond the state’s warning to form their own opinions.
"I don't think it would be responsible to say to people
that there's absolutely no health risks, but we're very near the legal
limit," Blackman said.
Alternatives to chlorine
"Standards are getting quite low in terms of the amount
of allowable contaminants. We, as well as other districts, are going
to need additional filtration equipment to remove the last remaining
organic compounds," said Blackman.
It might seem like the easiest way to prevent chlorine
byproducts is to stop using chlorine in the first place. But replacing
chlorine is costly, and the chemicals that are substituted are now suspected
of creating their own health problems. Improving filtration remains
the most trusted way to reduce disinfectant byproducts, and the most
cost-effective.
The BPUD is currently developing a pilot program that
will allow them to comply with not only the current standards but also
the subsequent, even-stricter standards that will arrive in 2012.
Fox said that IPUD is also trying to determine how
to comply with the new standards, but that the state hadn’t provided
a specific timeline for when the work needed to be completed.
As it stands, water quality in both districts is still
very good. Both Blackman and Fox said they used the minimal amount of
chlorine allowed by law.
For those who are still worried, simple carbon filters
from manufacturers Brita and Pur will remove most of the chlorine byproducts,
said Pablo Ramudo.
But Ramudo, who is water quality supervisor for the
North Marin Water District — which draws its water from wells and
is not in violation of federal standards — noted that some studies
say that chlorine byproducts are only a risk if inhaled, rather than
ingested. As is to be expected, there are other studies that say the
exact opposite.