Yesterday, April 30, a study on the increased risk of cancer from drinking California tap water made the news cycle. The news report, as we’ve come to expect, focused on grabbing your attention with a catchy headline: “Drinking California tap water for long period of time could increase cancer risk, study says” Don’t humans need to drink water for long periods of time (without water we die in days)?
Reading the article didn’t provide much context either. The article cherry-picked quotes or statements which made very little sense without the proper context. For example, there were these quotes:
“One person in a population of a million will develop cancer in their lifetime,” said Environmental Working Group scientist, Tasha Stoiber.
Is that good? 1 in 1,000,000 are pretty good odds, no? What is the overall rate of cancer in general?
“Arsenic is related to lung cancer and skin cancer, disinfectant bio products are associated with bladder cancer and other types of cancer,” said Stoiber
Yes, we can all agree arsenic is bad. But what were the concentrations observed? How far off a healthy range were they?
We all know chlorine is a toxic chemical we should not drink, yet we actively use it to disinfect our pools and drinking water. So the concentration we use is just as important as the chemical itself.
Finally, at the end of the article a little bit of context:
“Systems that had the highest cancer risk served smaller communities and served less than 10,000 residents”
OK, so NOT all of California’s water has the same level of risk. After all, California is a huge state with the largest population in the U.S. To say “California anything” does not really mean much unless you have context. Do you mean… Northern, Southern, Central, Coast, Mountains, Rural, Cities, Deserts?
Instead, we need to look at the actual report, to get the context this article was supposed to provide in the first place. There are a few things to note. The risk is not simply “highest” but much higher for smaller communities. The contribution percentage of drinking water to your chances of getting cancer in a lifetime vary widely.
Over 80% of the population has an average percent contribution to total drinking water-related lifetime cancer cases of 99%. Whereas the remaining 20% of the population have a 1% or less of the same contribution.
With over 2000 water systems in California, it is difficult to assert whether or not urban areas are safe by default (by simply taking population into account). Instead, you should check your actual water system using the EWG database
According to the report, arsenic is a major contributor to the risk of cancer. A paper they cite, notes about 40% of California’s population was exposed to the contaminant at concentrations above safe levels (anything more than 0.004 parts per billion). As an example, the water in Biola California has a concentration of arsenic of 2.2 parts per billion (ppb) in their water system. That’s 550 times above the healthy limit, but well bellow the 10ppb federal limit. Biola is a small water system serving about 1000 people.
By comparison, the Los Angeles water system which serves over 3 million people reported concentrations of arsenic of 300 times the healthy limit (1.2ppb). About half the concentration of Biola, but well above the recommended healthy limit.
Yet another large water system, the San Francisco regional water system, serving 2.5 million had no arsenic concentrations to report.
This brings us to the chances of 1 in 1 million of developing cancer over a lifetime (calculated as 70 years) from drinking water. According to the American Cancer Society, the most likely cancer to develop in males is prostate cancer with a rate of 1 in 9. The least likely is breast cancer (yes males can get it also) with a rate of 1 in 833. Females are at most risk of developing breast cancer at a rate of 1 in 8. The least likely form of cancer for females is Larynx at 1 in 833.
In other words, drinking California’s tap water will have a very small impact in our overall probability of developing cancer. I am not suggesting we ignore this. I am simply saying we need consider it within the overall subject. Sugar has a much bigger and direct impact in our chances of developing cancer and other diseases.
In conclusion, rather than panic and heading to the store to pick up a case of bottled water, checkout the EWG database and see if you need to purchase a water filter to reduce concentrations of chemicals that may be in your water system.
P.S. Sometimes, studies like these are sponsored by industry trying to guide a narrative to better serve their business. Fortunately, this does not appear to be the case for this study.
