Lead levels linked with peripheral neuropathy

Blood lead levels were significantly associated with peripheral neuropathy in a cross-sectional survey of 7,156 adults aged 40 and older.

The finding, from the 1999-2004 National Health and Nutrition Examination Survey, is of particular concern because the dose-response relationship was seen at blood lead concentrations, below 10mcg/dL, the level generally considered as the accepted threshold for concern by public health agencies, reported in a poster at the annual meeting of the Society of General Internal Medicine.

Previous studies have shown significant associations between blood lead levels greater than 30mcg/dL and peripheral neuropathy, but the blood level at which lead neurophatic toxicity begins has not yet been determined, said by the doctor and associates, of Beth Israel Deaconess Medical Center and Harvard Medical School, Boston.

Peripheral neuropathy defined as the presence of one or more insensate areas on either foot as assessed using a monofilament at three plantar metatarsal sites on each foot (hallux and first and fifth metatarsal heads) was found in 13.3% of the participants.

Compared with the participants who did not have peripheral neuropathy, those who did were considerably older (64 vs. 55 years), more likely to be male (54% vs. 38%), and less likely to have graduated high school. More of those peripheral neuropathy had diabetes and rheumatoid arthritis, and were more likely to be sedentary.

Geometric mean blood lead levels (measured using graphite furnace atomic absorption spectrophotometry) were 2.2 mcg/dL among those with peripheral neuropathy and 1.8mcg/dL among those without.

Compared with the participants whose blood levels were less than 3 mcg/dL and after adjustment for age, sex, race/ethnicity, education, diabetes, arthritis, health status, activity level, height, weight, alcohol intake, smoking status, renal function, blood glucose and serum B12 level the odds ratio for having peripheral neuropathy was 1.22 for subjects with blood lead levels of 3,004.99 mcg/dL, and 1.53 for levels of 5,009.99 mcg/dL.

This finding adds to the growing body of evidence suggesting lead exposure even at low concentrations may have important health risks. They are in a great place with lead levels right now, compared to where they were before lead was taken out of gasoline. The question is whether there are more health benefits that they could gain by eliminating more lead.