Hair as a biomarker of Mn Exposure

February 28, 2013

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Smith is a Professor of Microbiology and Environmental Toxicology at the University of California, Santa Cruz

Photo courtesy of Donald Smith

Hair as a biomarker of Exposure

Bailey Schug

February 2013

Epidemiologists have long struggled to establish non-invasive, temporal methods to predict human exposure to chemicals. A new study by NIEHS grantee Donald Smith, Ph.D., from the University of California, Santa Cruz, describes a process to accurately, and non-invasively, determine levels of manganese (Mn) exposure in children and adults, and thereby better evaluate health risks from exposure.

There is clear evidence that elevated Mn exposure in children and adults can lead to neurological deficits, including cognitive, behavioral, and neuromotor function problems. However, the Achilles heel of environmental epidemiology is exposure assessment. Researchers have long struggled with the challenge of developing methods to measure human exposure over meaningful time frames. This study contributes to this ongoing challenge by showing that systematic assessment of specific biomarkers is needed to relate exposure to adverse health outcomes.

Hair levels reflect exposure over time

Studies have suggested that levels of Mn in blood or urine may not reliably reflect environmental exposure. However, since hair grows relatively slowly, and since Mn is incorporated from blood into hair during hair growth, hair may reflect and integrate over several months changes in body Mn levels due to exposure.

As Smith explains, “in the simplest terms, hair Mn levels may reflect environmental Mn exposure over the period of hair growth (e.g., months) better than other commonly used exposure biomarkers, such as urine or blood”. If there exists a better (i.e., more accurate) biomarker of exposure, then the relationship between exposure and health effects may be more accurately determined.

High tech methods to measure Mn in hair

Smith’s group developed a hair cleaning method using ICPMS, scanning electron microscopy, and laser ablation. Exogenous metal contamination on hair that was untreated or intentionally contaminated with dust or Mn-contaminated water was removed using a sequential cleaning method employing detergents and weak acid.

The cleaning method was then used on hair samples from children in an ongoing study of environmental Mn exposure and related health effects. Hair samples were collected from children as part of an on-going epidemiologic study of environmental Mn exposure from ferroalloy plant operations in northern Italy. Studies have documented elevated air, dust, and soil Mn levels in the homes and schools near historically or currently active ferroalloy plants.

According to the study, the utility of using hair as a biomarker of Mn rests in large extent on the ability to reduce Mn from external contamination without altering metabolically incorporated Mn. The cleaning method Smith’s group developed  to remove exogenous contaminants enhances the validity and utility of hair Mn (and other metals) levels as an exposure assessment method.