A metal used in electronics and lightbulbs is associated with an increased risk of stroke, according to a new study.
Researchers from the University of Exeter found that higher urinary concentration of tungsten is associated with an increased stroke risk, even when taking into account other stroke risk factors such as age, socioeconomic status, cigarette use, body mass index, occupation and alcohol consumption.
Tungsten exposure is not thought to be high for the general population, though people can be exposed to it through drinking water, diet and the atmosphere. However, "recent reports have suggested that tungsten should be considered as an emerging chemical toxicant of concern," the researchers wrote in the PLOS ONE study. They explained why:
When soil pH falls, tungsten becomes increasingly soluble and can leach into underlying aquifers. With production of tungsten steadily rising (72,000 tons produced last year compared to 40,000 tons in 2002), and use becoming more widespread, the potential for tungsten to further contaminate the environment is increasing. Tungsten is known to be capable of biological interaction and disruption of biochemical pathways and therefore the human health impact must be considered.
While tungsten is not known to cause any health problems on its own, studies in animals and in cell cultures have linked it to cancer and pulmonary inflammation; other research has also suggested it could be associated with heart risks.
For the study, researchers examined urinary tungsten concentrations of 8,614 people between ages 18 and 74 who were part of the National Health and Nutrition Examination Survey. The researchers tracked them between 1999 and 2010.
The researchers found an association between higher levels of tungsten in urine and higher stroke risk. Some people were more likely than others to experience high tungsten levels, including blacks and Hispanic Mexicans, people with low body mass index, and people with lower incomes and education levels. The association between tungsten and stroke was especially pronounced in women, as well as people younger than age 50.
While other metals that are sometimes alloyed with tungsten -- such as nickel and copper -- could also potentially play a role in the stroke finding, "our findings point to tungsten as being of critical importance in stroke etiology of many of the cases considered here," the researchers wrote.