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Cancer-Causing Dioxane in the Groundwater of East L.A.

Are trace amounts of an industrial solvent increasing and should we worry?

By C.J. Salgado
Published on LatinoLA: August 17, 2014


Cancer-Causing Dioxane in the Groundwater of East L.A.


Years ago, as an aircraft maintenance technician in the Air Force, I had to work with a nasty industrial solvent, methyl ethyl ketone (MEK), used to clean aircraft parts. Think of a solvent like a paint remover. Besides being flammable, MEK can irritate the skin, eyes and nose. So, when I left the service, I was glad to be done worrying about solvents.

Until now As, apparently, I may be drinking some! You see, another solvent, "1,4-dioxane" (dioxane) has been detected in some groundwater wells of East L.A. for years.

Like MEK, dioxane is an industrial solvent. Despite having a "faint pleasant odor," it, too, is an irritant in short-term exposures. As for long-term exposures, studies indicate that dioxane can damage the liver and kidneys. More so, the state of California has classified it as causing cancer. Plus, it has been classified by the U.S. Environmental Protection Agency (EPA) as "likely to be carcinogenic to humans," based on animal testing. In fact, some of these animal studies involved mice and rats being given dioxane in drinking water over two years.

Although, a similar cancer risk assessment to humans does not necessarily follow an extrapolation from animals, the weight of evidence cannot be entirely dismissed. So, what is the increased risk for cancer from drinking dioxane-contaminated water? According to the EPA, at a concentration of 3.5 PPB (parts per billion of water) of dioxane in drinking water, the risk level of cancer is 1 in 100,000 for a 154-pound human drinking about a half-gallon of water per day.

So, what is the concentration of dioxane in the water of East L.A.? Data from groundwater wells operated by California Water Service Company (Cal Water), which services the East L.A. District, show that in recent years dioxane levels have seemingly been trending up with an upper range and highest annual average in PPB as follow:

Year--- Range--- Average
2013--- 8.5--- 4.2
2012--- 8.2--- 4.1
2011--- 7.4--- 3.5

In light of that risk, should we be worried? Well, we take other risks like when we step outside to drive our cars or climb up a ladder to clear our gutters. Here, that risk comes to us in that glass of crystal clear water of which we seldom think twice about before drinking. In fact, drinking water from local groundwater wells gets blended with purchased water from outside the area. That should, conceivably, lower the concentration of dioxane.

So, we should be okay, right? I mean, the odds it will hurt us can't be that bad. The bet is that assessing the true risk is more complicated in reality than what I've outlined in the preceding discussion with an outcome in our favor, we hope.

Okay, we know it's there in the groundwater but where is it coming from? Dioxane is used in many commercial products like resins, oils, and waxes, inks and adhesives, as well as in industrial applications like paper and chemical manufacturing. For example, it is used to dissolve cellulose-containing material, i.e., wood pulp. So, there can potentially be many man-made sources in the local area.

According to a Cal Water consumer report, "The water sources in the East Los Angeles system are considered most vulnerable to contamination from gas stations, confirmed leaks, known contaminant plumes, chemical/petroleum storage, metal fabrication, and plastic producers."

In addition, dioxane mixes easily with water, is a clear liquid, has a sweet odor, does not stick to soil (which means it can move into the groundwater), and is stable so it does not break down in water. In addition, conventional water treatment technology like carbon adsorption and reverse osmosis is ineffective at removing dioxane from water. Rather, it requires more specialized technology like ultraviolet light oxidation to treat. How's that for a perfect contaminant in water!

Interestingly, dioxane is technically not a regulated contaminant in our drinking water. Rather, state regulators utilize a "notification level" (NL= 1 PPB) system which is a "health-based advisory level for an unregulated contaminant in drinking water." Basically, if a groundwater well exceeds the NL, they let the state and consumers know, but if the concentration exceeds by 35 times the notification level, i.e., 35 PPB, a corresponding cancer risk of 1 in 10,000, then the state recommends the well be taken out of service.

Well, most likely, we're okay despite these trace amounts in our groundwater. However, what is undeniable is that water quality matters. We cannot afford to ignore any contaminant in our water that may have the potential to harm us or, particularly, our kids and elders. Dioxane is in the groundwater, possibly increasing, so we best monitor it properly.

Doing exploratory data analysis and further characterization may be needed to better gauge the scope of the problem not only in East L.A. but in the greater region, too, as dioxane has also been detected in other areas of Southern California. In addition, we may want proposed new state legislation addressing groundwater pumping to contain a specific provision to monitor for this.

Do I care for solvent in my drinking water? No, thank you, I'll take my water served straight up!

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