An Environmental Protection Agency (EPA) mandate to reduce concentrations of arsenic in public water systems has resulted in the prevention of hundreds of cancers each year since 2006, the year the rule was put into effect, in according to projections in a new study.
There are now fewer cases of lung, bladder, and skin cancer cases each year in the United States because exposure to arsenic in drinking water is meaningfully lower than it was prior to the introduction of a legally mandated intervention to reduce arsenic concentrations in public water systems, say the authors, led by Anne Nigra, PhD of the Columbia University Mailman School of Public Health, New York City.
The researchers determined their estimates as part of a longitudinal analysis of the National Health and Nutrition Examination Survey (NHANES).
In contrast, no reduction in exposure to arsenic was detected among US residents who drink water mostly from private wells. Private wells are exempt from the 2006 legislation to reduce maximum contaminant levels of arsenic in public water systems.
“For public water users, we estimated a reduction in water arsenic exposure of 17% from 2003 to 2014, which represents a substantial exposure reduction when applied at the population level,” study authors observe.
“Assuming these estimated exposure reductions will remain similar across a lifetime, we estimated a reduction of 200-900 lung and bladder cancer cases or 50 cases of skin cancer per year depending on the approach used,” they add.
The study was published online October 22 in Lancet Public Health.
Data from six cycles of NHANES from 2003 to 2014 were used to assess population levels of dimethylarsinate (DMA), the main metabolite of inorganic arsenic in human beings, along with total urine arsenic to track exposure to arsenic in the drinking water among survey participants.
In 2006, the EPA mandated that the maximum contaminant level of arsenic in public water systems be 10 ug/L, down from 50 ug/L prior to introduction of the legislation.
However, public authorities were allowed time to reduce arsenic levels to the new maximum EPA level, so changes in population levels of DMA were not expected right away.
The investigators then compared urinary arsenic measurements from 14,127 NHANES participants in the 2003-2004 cycle prior to the introduction of the EPA mandate to those from the 2013-2014 cycle, when they assumed that public authorities had achieved the new maximum contaminant levels of 10 ug/L.
Geometric means of urinary DMA and total arsenic were compared for each 2-year cycle for participants who reported that they drank mostly tap water, as well as for those who relied mostly on well or rain cistern water as their primary source of drinking water.
The geometric mean of urinary DMA levels among participants who mostly used tap water did not change between NHANES 2003-2004, during which they were 3.01 ug/L, and NHANES 2009-2010, during which levels were similar, at 2.93 ug/L.
This lack of change mostly reflects the fact that it took municipal authorities a fair amount of time to comply with the new EPA maximum contaminant regulations, the study authors explain.
However, between NHANES 2011-2012 and NHANES 2013-2014, geometric mean of urinary DMA dropped from 2.64 ug/L to 2.49 ug/L.
In contrast, the geometric mean of urinary DMA increased slightly from 2.38 ug/L to 2.59 ug/L between NHANES 2003-2004 and NHANES 2013-2014 among participants who reported that private wells were their main source of drinking water.
However, for private well users, “the overall trend was not significant,” the authors note.
Significantly, Mexican-Americans who drank mostly tap water seemed to benefit the most from the EPA 2006 mandate. The geometric mean of DMA in this subgroup of NHANES participants dropped from 4.06 ug/L in 2003 to 2.58 ug/L in 2014, a 36% reduction in geometric mean DMA across the 10-year longitudinal survey (P < .001).
Total Arsenic Levels
Changes in total arsenic levels were more variable in public water users and in users of private well water, but they decreased more among participants who drank mostly tap water from the earlier NHANES survey levels to later levels in 2011-2012.
Among private well users, the geometric mean of total arsenic across the six consecutive NHANES cycles was highly variable.
Again, geometric mean of total arsenic among Mexican-Americans showed the most robust reductions, dropping from 6.05 ug/L in 2003 to 3.18 ug/L in 2014, a 47% reduction in total arsenic exposure across the decade-long survey (P < .001).
It is well established that in many cities in the southwest, public water supplies come from water sources with naturally high levels of arsenic. Those cities include Los Angeles, California; Albuquerque, New Mexico; Scottsdale, Arizona; and Tucson, Arizona.
The “markedly stronger” decrease in exposure to arsenic among Mexican-Americans therefore reflects the fact that many cities in the southwest invested in the infrastructure needed to ensure they met EPA maximum contaminant standards of 10 ug/L of arsenic in their drinking water systems.
“No previous study has compared arsenic exposure concentrations in populations served by public water systems or private wells in the USA,” the authors write.
“The decrease in urinary arsenic in public water users in NHANES 2003-14 supports the hypothesis that the implementation of the current arsenic maximum contaminant level regulation has reduced arsenic exposure in the general US population,” the investigators state.
At the same time, they point out that efforts are still needed to reduce arsenic exposure from household well water, which are not subject to EPA standards.
As of 2017, no state government had mandated that homeowners install treatment systems in private wells, even when test results indicate that arsenic concentrations exceed maximum contaminant levels.
Approximately 45.5 million Americans rely on private wells as their primary source of drinking water.
Accompanying Editorial
Commenting on the study in an accompanying editorial, Philip Landrigan, MD, Icahn School of Medicine at Mount Sinai, New York City, points out that it is critical to consider not just the cost of putting environmental protections in place ― anathema to the Republican Party, which has long held that environmental protection efforts are “unduly burdensome” ― but to consider the overall costs savings to society by preventing diseases and deaths.
“Arsenic is a major public health problem, and apart from exposures in the workplace, drinking water is the main source of exposure worldwide,” Dr Landrigan writes.
The current longitudinal NHANES findings are not only consistent with those from previous studies demonstrating the health benefits of reducing arsenic concentrations in public drinking water, but they are also concordant with reports of the health benefits from reducing air pollution, he points out.
For example, since passage of the Clean Air Act in 1970, six common air pollutants have been reduced by 70%, yielding an estimated economic benefit of $30 for every dollar invested, Dr Landrigan notes, despite the fact that the gross domestic product has grown by almost 250% since the Clean Air Act was passed.
“Government leaders who might be tempted by the siren call of deregulation, blinded by its promised short-term economic benefits, and pressured by powerful vested interests opposed to any form of environmental control, need to pay attention to these findings,” Dr Landrigan warned.
“Environmental pollution is now recognized to be a major cause of disease, death, and environmental degradation,” he adds.
“Interventions to control pollution provide an extraordinary opportunity to improve public health and also to slow the pace of global climate change,” Dr Landrigan concludes.
Separate Study
In a separate study published online October 24 in the Journal of the National Cancer Institute, researchers found that mortality from lung, bladder, and kidney cancer due to high arsenic exposure was both excessive and persisted for many decades.
The researchers, with lead author Allan Smith, MD, PhD, University of California, Berkeley, explain that in 1958, there was a sudden increase in arsenic concentrations in the drinking water in the northern Chilean city of Antofagasta.
A major reduction in exposure to arsenic contamination occurred in 1970 when city officials installed an arsenic removal plant.
From 2001 and 2010 ― forty years after efforts to reduce exposure to arsenic in Antofagasta ― men living there were more than three times as likely to die from lung and bladder cancer than men living in the rest of Chile (P < .001). Women in Antofagasta were twice as likely to die of lung cancer and were almost fives times as likely to die of bladder cancer than women living in other areas of Chile during the same period.
Mortality from kidney cancer was approximately twice as high for both men and women exposed to high levels of arsenic 40 years after reduction efforts had been introduced (for both men and women, P < .001).
“[This study] provides clear evidence that lung, bladder, and kidney cancer mortality for both men and women remained elevated up to 40 years after very high arsenic exposures ended, indicating very long latency patterns,” the investigators conclude.
“These findings not only add important scientific information on latency patterns that may be as long or longer than for any other cause of cancer, they also have direct
public health implications. The long latency after exposure reduction
means the incidence of arsenic-related diseases is likely to remain very high for many years after arsenic exposures have stopped, highlighting the importance of eliminating exposures as soon as possible,” the investigators conclude.
Dr Nigra, Dr Landrigan, and Dr Smith have disclosed no relevant financial relationships.
Lancet Public Health. Published online October 22, 2017.
J Natl Cancer Inst. Published online October 24, 2017.
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