Thanks to Follower Franck for today’s topic.
Apparently, Franck has too much free time and disposal income, because he recently took a vacation to Sequoia National Park. You know, the park in California with the huge trees, such as the General Sherman shown in today’s photo. And along with the big trees you’ll find towering mountains, beautiful meadows, rushing streams, placid lakes, and … poor drinking water quality!
Franck says he was given a written notice that the total trihalomethane level was 102.3 micrograms per liter, and the haloacetic acid level was 124.3 ug/L. When he inquired about the written notice, he was told that the water was safe to drink. So, why the notice in the first place? And was the water really safe to drink? And how could this happen in an area with such pristine water?
Hey, one question at a time, Franck!
First, these two violations needed to be reported to consumers of the drinking water, because they are violations of primary drinking water standards — the ones that are directly related to public health. The notice was a requirement of federal law. The Environmental Protection Agency required the Department of the Interior (in charge of all things outside, oddly enough!) to make this notice. Two federal agencies and millions of confused park visitors! But rules are rules, and the rules required the notice.
Both the THMs and the HAAs are disinfection by-products, formed when a disinfectant — usually chlorine — combines with natural organic matter (NOM) in the water. The fact that a disinfectant was added is definitely good news: it means the chance of getting diarrhea from the water was very low. The chlorine is there to kill the microorganisms that cause such diseases, but what happens to the little critters when they die? They are blown to smithereens by the chlorine, and the little pieces that remain in the water are disinfection by-products, or DBPs.
A small number of these DBPs are regulated as primary standards. But the risk they pose is not immediate — as it is with the microorganisms. Instead, DBP regulations are based on consuming 2 liters of water every day for 70 years at the maximum contaminant level (80 ug/L for THMs and 60 ug/L for HAAs.) Consuming at these levels results in a theoretical incremental increase in cancer risk of about 1 in 100,000. Since around 30,000 people out of 100,000 will contract cancer during their life, this means that drinking water with DBPs at the MCL theoretically will make you number 30,001. Those are lottery odds! So, I think the ranger was accurate in telling you that the water was safe to drink. The water was probably a lot safer than the food and beverages at your camp site, Franck!
Finally, how could this happen in an area with such pristine water? Well, first off, we need to get past this “pristine” term. There is no such thing! Essentially, ALL water is contaminated — even in a national park. That’s because the water molecule is so “gregarious” — it loves to invite other substance to enter the water. This is why water is called the Universal Solvent. As soon as the water falls from the sky — and even on the way down! — “contamination” begins.
The greatest public health risk is from waterborne diseases caused by microorganisms, which account for thousands of deaths around the world each day. The act of putting chlorine in the drinking water at Sequoia prevents these deaths for the park attendees — nice job, National Park Service! But the extremely strict water quality standards imposed by the EPA attempt to protect water users from even very small risks, such as DBPs. Controlling the DBPs in small systems like we might find in campgrounds is extremely complex and costly. And with the federal budget situation being the mess that it is, I wouldn’t want to spend any money at all to address the minuscule risk presented by DBPs.
Make sure you report back to me after your next vacation, Franck!