Exposure to cadmium, even at low levels, can put you at significantly higher risk for diseases associated with aging, says a new study from a George Washington University researcher.
Ami Zota, a professor in the Milken Institute School of Public Health, and her colleagues found that the heavy metal is associated with the shortening of telomeres, DNA protein complexes that cap the end of chromosomes and protect them from deterioration.
When telomeres get too short, the cell can no longer divide, which can lead to health problems such as cardiovascular disease, diabetes and even early mortality. Telomere shortening is a normal part of getting older, Dr. Zota said, but cadmium exposure seems to speed up the process.
“By identifying modifiable, preventable factors that accelerate telomere shortening, this can become a way to prevent disease,” Dr. Zota said.
The U.S. Department of Health and Human Services has determined that cadmium can cause certain types of cancer, and the World Health Organization (WHO) has warned against its harmful effects.
Cadmium is released into the environment from mining and metal processing operations, burning fuels, using phosphate fertilizers and disposing of metal products, according to the Environmental Protection Agency. It can enter your blood stream by eating and drinking cadmium-contaminated food and water and by breathing contaminated air. People who work at or live near industrial sites that burn fossil fuels like coal or oil are particularly at risk.
Cigarette smoke is another source of exposure, since tobacco plants tend to absorb a lot of the toxic chemical from contaminated soil. Smokers have about twice as much cadmium in their bodies as non-smokers, the EPA says.
“In some ways it is more toxic than lead, but it occurs at lower levels in the environment, so there tends to be less of it,” she said.
Past research has linked shortened telomeres to premature aging, but Dr. Zota’s study, published in the American Journal of Epidemiology in December, is the largest to date that looks at the relationship between cadmium exposure and telomeres.
“There has been quite a bit of research looking at genetic determinants of telomeres as well as lifestyle and psychosocial factors,” Dr. Zota said. Many studies, for instance, have linked chronic stress to telomere shortening.
“However, environmental factors have been left out of the picture. There seemed to be a big gap in the literature.”
The Study
The researchers analyzed blood and urine samples from more than 6,700 adults who participated in the National Health and Nutrition Examination Survey from 1999 to 2002, a nationally representative health survey of the U.S. population. They obtained purified DNA from blood cells and then used a genetic technique known as polymerase chain reaction to measure the telomeres.
They found that people with the highest concentrations of cadmium in their bloodstream had telomeres that were about six percent shorter than those in the lowest group. Their cells looked on average 11 years older than their calendar age.
As predicted, the researchers also found a strong link between smokers and shortened telomeres. Their findings also suggest that the cadmium, in particular, is one of the main ingredients in cigarette smoke that leads to accelerated cellular aging.
“There is a robust association between shorter telomeres and cigarette smoke that has been published in multiple studies,” Dr. Zota said. “My analysis suggests that the relationship between cigarette smoke and shortened telomeres is at least in part, due to cadmium.”
The researchers are careful to note in their study that they would need additional research to prove that exposure to cadmium definitively causes telomeres to shorten.
Despite these limitations, Dr. Zota said she was especially surprised to find that even relatively low levels of cadmium can elicit harmful effects on biological health.
To reduce environmental and occupational exposure to cadmium, WHO has recommended banning smoking in public places, finding ways to reduce cadmium emissions from mining and promoting effective measures to increase recycling of the metal.
Results from Dr. Zota’s study further underscores the need for public health policies to curtail human exposure to cadmium.
“We’re seeing these measurable, harmful effects well below the levels of current safety standards used by environmental agencies,” Dr. Zota said. “This research continually feeds into revisiting what is ‘safe’ and changing that paradigm.”
