Exposure to arsenic through drinking water has long been recognized as a serious risk to human health. This month, two studies underscore the extent of the ongoing threat, presenting fresh evidence regarding how arsenic exposure contributes to antibiotic resistance, and how the overall health risks are disproportionately borne by Hispanic and American Indian communities.
“Reducing exposure to arsenic is important given the numerous health effects,” said Ana Navas-Acien, a professor of environmental health at Columbia University and an author on a new study identifying racial and ethnic inequalities associated with arsenic pollution.
Arsenic is naturally occurring in the earth but is highly toxic in its inorganic form. It has been used for decades for a range of industrial purposes. Long-term exposure to the chemical is associated with some cancers as well as developmental problems, an increased risk of diabetes, pulmonary disease and other diseases, according to the World Health Organization (WHO).
An estimated 140 million people in at least 70 countries have been drinking water containing arsenic at levels above the WHO provisional guidelines, the organization states.
Looking at arsenic exposure and antibiotic resistance, authors of a new study published in PLOS Pathogens analyzed water samples from rural Bangladesh and stool samples from women and children living there, finding that those exposed to high levels of arsenic also had a higher occurrence of antibiotic-resistant E. coli bacteria.
The findings warrant “redoubling efforts to reduce arsenic exposure,” the authors wrote. Antibiotic-resistant bacteria are a public health concern since diseases caused by such bacteria, which can be deadly, are harder to treat. Individuals infected with antibiotic-resistant bacteria often have higher medical costs, longer hospital stays, and worse health outcomes.
“Bacteria in arsenic contaminated environments are more likely to be resistant to antibiotics compared to arsenic-free environments,” said Mohammad Aminul Islam, a Washington State University professor and author of the study.
Some bacteria use the same biological mechanisms to resist the toxicity of arsenic and many common antibiotics. Water high in arsenic kills off bacteria without resistance, leaving only the bacteria that is resistant to both arsenic and antibiotics.
“In parts of the US where there is a high level of arsenic contamination in the groundwater, and if people consume the contaminated water on a regular basis, it is likely that we would see a similar trend,” said Islam. He said more research within the United States would be needed to determine if this is the case.
According to data collected by the Environmental Working Group from 2017-2019 sampling, arsenic contamination was found in drinking water above the EPA’s legal limit of 10 parts per billion in 31 states, with 543,000 people possibly impacted. Texas and California had the highest number of utilities with arsenic contamination, in line with the results of the Columbia team’s study.
Communities of color
Arsenic contamination is a particularly significant concerns for many Hispanic and American Indian communities, making its effects an environmental justice concern, especially since these communities already suffer from other sources of pollution.
The Columbia University study published this month in Nature Communications found that higher populations of Hispanic/Latino and American Indian/Alaskan Native residents are associated with high arsenic concentrations — more so than for other racial and ethnic groups.
Hispanic/Latino people make up a larger proportion of the population in the southwestern US, where arsenic and other heavy metals occur at higher levels in drinking water, the authors wrote. Many counties in Nevada, California, Arizona, New Mexico, Texas, Kansas, and Nebraska were identified as hot spots for arsenic contamination.
Navas-Acien said there could be many reasons behind the trend. One hypothesis is that the discrepancies are related to a lack of resources in these communities that make issues of water infrastructure difficult to address, she said. “Structural racism likely underlies these inequalities,” write the authors of the paper.
More financial and technical support to address arsenic and other heavy metal pollution can “help protect communities of color,” write the authors of the Columbia University study. In New Jersey, for example, residents with contaminated well water can receive a zero-interest loan to install a treatment system in their house.
The areas of the country identified in the analysis by the Columbia researchers overlap with much of the US’s agricultural lands, specifically land where livestock production is prevalent, such as in northwest Texas and California’s San Joaquin Valley. Both regions also have high Hispanic/Latino populations and are considered some of the most polluted areas of the country; in addition to arsenic concerns, the San Joaquin Valley especially suffers from dangerous air pollution.
Regions of the country with dense animal agriculture may also be impacted by increased instances of antibiotic resistance due to contamination from nearby feedlots, as dust from feedlots has been shown to carry antibiotic-resistant genetic material. The WHO lists the agricultural sector as one area of focus to help prevent the proliferation of antibiotic resistance.
“Current US public drinking water infrastructure, management, and regulatory action does not adequately protect communities of color,” write the authors of the Columbia study.