6 December 2011

Got arsenic? Social disparities in drinking water quality

Posted by kramsayer

Poorer, minority communities in the San Joaquin Valley have higher levels of arsenic and nitrates in their drinking water. (Credit: Ildar Sagdejev/Wikimedia commons)

Running around between sessions at the American Geophysical Union’s Fall Meeting, I’ve found myself relying heavily on the drinking fountains scattered throughout the convention center. I repeatedly refill my bottle and go on my way, taking for granted my ability to slurp down safe, clean water.

Although many people in the United States don’t often think water quality is a major issue, access to safe drinking water is an emerging problem in this country, says Isa Ray, associate professor at the University of California, Berkeley. During her Monday afternoon talk at the meeting, Ray showed that water systems in the San Joaquin Valley that serve higher proportions of minority residents, or that serve areas where residents are not homeowners, have higher levels of contaminants.

The science of hydrology readily lends itself to policy applications through water management issues. Scientists can measure and predict variation in rainfall, snowpack and drought to help water managers decide how much of the resource to allocate to houses, farms and businesses. However, few researchers have explored whether social disparities exist in access to that water, Ray says.

Ray and her colleagues were interested in the San Joaquin Valley for several reasons.  The area is highly diverse: 46 percent of the population is Latino and 41 percent are non-Hispanic people of color. Additionally, 20 percent of the population is below the poverty level.

Ray and her team focused on two key contaminants: nitrates, which often stem from fertilizers in agricultural runoff, and arsenic, a naturally-occurring mineral. Both carry serious health concerns. Excess nitrates can cause blue baby syndrome, a disorder that results when nitrate reacts with hemoglobin and reduces its capacity to carry oxygen.  Risks associated with arsenic include skin damage and certain cancers.

The researchers pulled nitrate and arsenic concentrations from water quality monitoring data at community water systems. They then used census data to estimate the community demographics around each water system using census data. Since incomes are highly variable in the area, the researchers used home ownership as a measure of socioeconomic status. Typically, only those with homes are allowed to participate in water decisions, Ray said, so home ownership is also a measure of political clout.

The team found that increased nitrogen levels were associated with communities with a higher percentage of Latino residents and a decreased percentage of homeowners. The trend was not statistically significant for the overall data set, but was significant when the team looked just at small water systems that served 200 people or fewer. The researchers also found that arsenic concentration decreased by 0.27 microgram per liter for every 1 percent increase in home ownership, a relationship that was significant for all community water systems as well as small ones.

Ray says that often in discussions of environmental justice, many people will want to blame the disparities as simply a matter of scale: smaller systems may simply have a smaller capacity to mitigate or treat their water problems.  However, her research shows that within the small systems, poorer and more Latino communities face greater burdens of exposure and costs of complying with water standards. These communities often have fewer resources to minimize their contaminant exposure.

“You could probably find a system in Beverley Hills that serves 200 or fewer residences, but you wouldn’t have these issues,” Ray said. “It’s the power of the community that makes the difference.”

- Erin Loury is a science communication graduate student at UC Santa Cruz