Researchers have found an increased incidence of end-stage renal disease(ESRD) in adults with high blood lead levels as a result of occupational and environmental sources. This mainly results from:
- inhalation of lead particles generated by burning materials containing lead, e.g. during smelting, informal recycling, stripping leaded paint and using leaded gasoline; and
- ingestion of lead-contaminated dust, water (from leaded pipes), food (from lead-glazed or lead-soldered containers).
Important sources of environmental contamination include mining, smelting, manufacturing and recycling activities. More than three quarters of global lead consumption is for the manufacture of lead-acid batteries for motor vehicles(WHO).
Lead is, however, also used in many other products, for example pigments, paints, solder, stained glass, crystal vessels, ammunition, ceramic glazes, jewellery, toys and in some cosmetics and traditional medicines. Drinking water delivered through lead pipes or pipes joined with lead solder may contain lead. Much of the lead in global commerce is now obtained from recycling.
Key facts about Lead:
- Lead is a cumulative toxicant that affects multiple body systems and is particularly harmful to young children.
- Childhood lead exposure is estimated to contribute to about 6,00,000 new cases of children developing intellectual disabilities every year(WHO).
- Lead exposure is estimated to account for 1,43,000 deaths per year with the highest burden in developing regions(WHO).
- Lead in the body is distributed to the brain, liver, kidney and bones. It is stored in the teeth and bones, where it accumulates over time. Human exposure is usually assessed through the measurement of lead in blood.
- There is no known level of lead exposure that is considered safe.
- Lead poisoning is entirely preventable.
According to the study, the investigators mainly found excess risk for ESRD only among men in the highest blood lead level category (above 51 μg/dL). In these subjects, the incidence of ESRD was 1.47 times greater than would be expected in the general population, with the incidence higher for nonwhites than whites (2.12 times greater vs. 1.14 times greater). Ritam Chowdhury, PhD and team from Emory University in Atlanta observed that high lead exposure exacerbates the already high underlying risk for the nonwhite group.
At a blood level threshold of 50 μg/dL, the Occupational Safety and Health Administration (OSHA) requires removal of construction workers to a lower exposed job until their blood lead level falls to below 40 μg/dL, the research pointed out. For other workers, these limits are 60 μg/dL or higher on a single test or a series of recent tests averaging greater than 50 μg/dL.
“Given that repeated intermittent high exposures can lead to a high body burden over time, which may lead to kidney damage, the precautionary principle would suggest that the present OSHA standard, even if consistently enforced, may not be sufficiently protective,” the research team at Emory University summarized.