Previous estimates assumed low level lead exposure did not increase risk of premature death, however this study finds that low level lead exposure does increase risk of premature death at levels between 1-5 micrograms of lead per decilitre of blood, especially from cardiovascular disease. Exposure to lead is linked to ischemic heart disease, high blood pressure, and hardening of the arteries. Lead particles that remains in the environment from paint and plumbing, fuel use, and ongoing exposures from foods, paints, lead batteries, industrial emissions, and contamination from lead smelting sites are responsible for lead exposure.
To conduct this study data was analyzed from NHANES-111 which included 14289 people aged 20+ from within the USA. All participants had a full medical examinations conducted which included testing the blood for lead, and urine test for cadmium. 4422 people died including 1901 from cardiovascular disease and 988 from heart disease after an average of 19.3 years.
Average lead found in participant blood was 2.7 ug/dL ranging from less than 1 to 56 ug/dL. 3632 participants had levels of 5 ug/dL or higher with the highest levels found in participants that were older, smoke, less educated, drank alcohol, more likely to be male, high cholesterol, more likely to have diabetes or hypertension, and had less healthy diets. 1 in 10 participants were found to have had lead levels that were undetectable to blood testing.
Participants with high lead levels at 6.7 ug/dL+ were found to be 37% at greater risk of premature death due to any cause, 70% greater risk of cardiovascular death, and at double the risk of death from ischemic heart disease. These risk levels were used to estimate current proportion of death in adults aged 44+ within the USA that could have been prevented if lead exposure had not occurred.
It was found that overall 18% of all deaths within the USA each year would be people with lead levels above 1 ug/dL; and estimated that 28.7% of premature cardiovascular deaths could be linked to lead exposure; and 37.4% could be link to ischemic heart disease linked to lead exposure. Results were adjusted for factors such as sex, household income, age, BMI, diet, smoking, ethnic origin, diabetes, amount of cadmium in urine, and physical activity. It was noted that these numbers are comparable to the annual number of deaths within the USA related to smoking, with the risk being lower but more prevalent across the population.
Some limitations may be that only one blood test was taken at the start of the study and can not determine if further exposure happened; also all potential confounding factor could not be controlled such as exposure to arsenic or air pollution.
This study has shown that lead exposure can have toxic effects at lower levels than was previously thought to be safe, having a greater impact than previously recognized. Low level lead exposure is currently mostly ignored as a risk factor for deaths from cardiovascular disease. Public health measure such as phasing out lead containing fuels, replacing plumbing lines, reducing emissions and pollution, and abating older homes will be vital to preventing lead exposure. Close to 1 in 3 cardiovascular deaths within the USA may be associated to low levels of lead exposure.
