A colorless, odorless and tasteless metal found in drinking water across the US has been linked to an increased risk for heart disease in a massive new study.
Researchers from Columbia examined the health records of 100,000 Californians over 23 years and compared it to their estimated exposure to arsenic in drinking water.
They found that people exposed to high levels of the toxic metal for a decade or more were 42 percent more likely to develop heart disease.
The link persisted even when controlling for factors like high blood pressure, smoking status and exercise habits.
Even drinking water that contained less than the EPA limit of 10 parts per billion over time led to a five to 20 percent increased risk of heart disease.
This, study author Dr Tiffany Sanchez, an environmental and molecular epidemiologist said, suggests that current policy on the amount of arsenic allowed into drinking water may need to be re-examined.
Dr Sanchez said: ‘Our results are novel and encourage a renewed discussion of current policy and regulatory standards’.
Previous studies by the US Geological Survey estimated that 2.5milllion Americans may get their water from arsenic-tainted drinking wells.
Dr Sanchez said: ‘This study is one of the first to comprehensively describe risks at exposure levels below the current regulatory limit.’
It’s unclear how arsenic may cause heart problems – but older studies in animals have shown that it may lead to inflammation that affects the shape of the blood vessels branching off the heart.
Changes in the shape of these blood vessels can affect how blood flows and cause damage to the organ over time.
Arsenic is a naturally occurring heavy metal found in the Earth’s crust that can get into air, water and soil.
It’s most concentrated in ground water in New England, the northern Midwest and parts of the West. California is one of those states.
The most common way people get exposed to the metal is through drinking water, according to the National Institute of Environmental Health Sciences.
People who use private drinking wells and don’t regularly test for arsenic are at a much higher risk than those who get their water from a community water supply.
The Environmental Protection Agency estimates that these utilities provide drinking water to 90 percent of Americans.
When someone is exposed to this tasteless, colorless and odorless in high amounts over a long period of time, it can cause damage to their cardiovascular, immune and endocrine systems. It can also build up in the liver, kidney, prostate and bladder.
Still, researchers are unsure just how much arsenic exposure over time can lead to heart disease.
The new study, which was published in the journal Environmental Health Perspectives by researchers at Columbia University Mailman School of Public Health, aimed to narrow in on that measurement.
It included an analysis of 98,250 people who participated in the California Teachers Study, which gathered data from over 100,000 teachers, nurses and other school staff from 1995 through 2018.
It tracked their lifestyle habits, location and health outcomes over time.
The Columbia researchers excluded people above 85 and those who had previous heart disease. Then, they compared the health data from the teachers to maps showing the amount of arsenic found in drinking water across California.
They looked at both ischemic heart disease and cardiovascular disease.
Ischemic heart disease, also known as coronary artery disease, has to do with a reduction of blood flow to the hear, because of plaque build-up or blood clots. According to the NIH, this is the leading cause of heart attack.
Cardiovascular disease is a catch-all term including stroke, heart disease, heart failure and peripheral artery disease.
A pattern emerged when looking at the 6,119 cases of ischemic heart disease and 9,936 of cardiovascular disease – linking arsenic exposure to coronary artery disease. There was no evidence of a link to cardiovascular diseases like stroke.
The current EPA limit for the acceptable amount of arsenic in drinking water is 10 parts per billion (ppb) of water.
About 48 percent of participants were exposed to less than one ppb of arsenic, and the researchers found they were not at an increased risk for developing heart disease. But people exposed to between one and ten parts per billion were.
When exposed to between one and five ppb, people were five to six percent more likely to develop ischemic heart disease.
When exposed to between five and ten ppb of arsenic, people’s risk of developing ischemic heart disease increased by 20 percent.
Finally, when exposed to levels above the EPA limit, people were 42 percent more likely to develop ischemic heart disease.
In addition to the amount of arsenic, the researchers looked to see if the amount of time that someone was exposed to arsenic-water mattered. They found the longer someone was exposed, the greater their risk was.
Once they hit a decade of exposure, their risk was about 18 to 20 percent higher than people who had been exposed to arsenic in drinking water for a shorter period of time.
These findings, though unique in their scope, are not the first to tie arsenic exposure to heart disease.
A 2018 study of Indigenous people living across the US found that those with higher levels of arsenic in their urine were 1.5 times more likely to have high blood pressure and thickened heart muscles.
Both of these factors are signs that the heart is put under stress, and may cause heart disease and interruptions to it’s rhythm.
Still, Dr Sanchez said, more research is needed before doctors can conclude that arsenic causes heart problems, and doctors are unsure how the metal may be causing the increased risk seen in the study.
Normally, a narrowing of the blood vessels and plaque build-up is blamed on poor diet choices, which cause cholesterol and fat to accumulate in the blood stream and clog up the tubing of the cardiovascular system.
It’s not clear how arsenic could be contributing to this.
Dr Sanchez concluded therefore that their findings are a jumping off point for further research: ‘We believe that the data and methods developed in this study can be used to bolster and inform future studies and can be extended to evaluate other drinking water exposures and health outcomes.’
