Chapter 4
Human Hair and Lichen
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Activities Involving the Use of Biomonitors in International Atomic Energy Agency Programs on Health-Related Environmental Studies 1
Susan F. Stone
International Atomic Energy Agency, Division of Human Health, P.O. Box 100, A-1400 Vienna, Austria Environmental studies have often involved the collection and analysis of non-biological (abiotic) samples such as soil, air and water, where trace element and other analyte concentrations are often at very low levels and where it may be difficult to distinguish or to interpret the results of the analyses. The collection and analysis of biomonitor samples has many advantages over abiotic samples, including bio-concentration of pollutants, simpler sampling techniques, more relevance of the information obtained on the biological significance of concentrations of specific pollutants, and providing a measure of integrated exposure over time. The International Atomic Energy Agency (IAEA) is including the study of biomonitors for evaluation of environmental status in its programmes on health-related environmental studies. Biomonitoring activitiesfromtwo co-ordinated research programmes are presented; the collection and analysis of human hair and that of lichens. In addition, quality assurance materials were developed and characterized in support of these activities. These materials include IAEA-336, Lichen, and two human hair materials, IAEA-085 and IAEA-086, the latter two with elevated and low levels of methylmercury, respectively. As the financial and manpower resources in many Member States are increasingly coming under pressure, the design of programmes for environmental studies is becoming more focused, especially in the number and types of samples that are taken. The data obtained from the collection and analysis of biomonitor samples is often less complicated and costly than other types of abiotic samples, and has the additional advantage of indicating which pollutants in the abiotic environment have a direct impact on the individual and populations of organisms, human and otherwise. The Nutritional and Health-Related Environmental Studies Section of the IAEA has included the study of biomonitors in several of its co-ordinated research programmes (CRPs); the 1
Current Address: 7038 Ridge Road, Frederick, MD 21702 © 1997 American Chemical Society
In Environmental Biomonitoring; Subramanian, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1997.
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Human Hair and Lichen
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monitoring of populations for methylmercury using human hair as a biomonitor, and the monitoring of air particulate matter and total deposition by collecting and analyzing lichen.
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Methylmercury and Human Hair The toxicity of high levels of methylmercury (MeHg) on the human nervous system has been well-established, through investigations of the poisonings in Minamata Bay in Japan and in Iraq. There are still significant inputs of mercury into the environment in many parts of the world, either through natural sources in mercury-rich environments, or via human activities, including gold mining areas (where large amounts of mercury are used in the extraction process), and areas with chloralkali plants and other industries. In aquatic systems, the elemental mercury that is discharged into the environment, either by natural sources or anthropogenically, is transformed by various mechanisms to methylmercury. There is a rapid accumulation of methylmercury through the food chain, and it is concentrated in predatory species offishand consumers of fish (e.g. mammals). In humans, the MeHg ingested through food items, such as fish, is almost completely absorbed into the bloodstream. Recently, there has been renewed concern over MeHg, due to the recognition that prenatal exposure at previously considered low levels of this mercury species can affect the developing nervous system (7,2). Although the general population is not atrisk,there is special concern about population groups with a high consumption of fish in their diets or live in areas with high mercury levels in the surroundings. Hair analysis has been established as an effective monitoring method for MeHg and isfrequentlyemployed in studies of mercury exposure (3,4). Compared with either blood or urine, the use of hair as a biomonitor is more widespread due to bioconcentration, ease of sample collection and the possibility of an integrated history of exposure, from months to even years. The determination of Hg and MeHg in hair has been the core of an IAEA research programme, "Assessment of Environmental Exposure to Mercury in Selected Human Populations as Studied by Nuclear and Other Techniques". The programme was aimed at identifying population groups which might be atriskfromelevated methylmercury intake from diet, and method development and validation were specifically stressed. There have been indications that hair mercury levels as low as 6 mg/kg in pregnant women are correlated with effects on the developing fetal nervous system (5,6). In view of these indications, the emphasis of the studies in the CRP has been on pregnant women and their babies. Table I gives a list of the participants of the co-ordinated research programme, their respective institutes, and the population areas being monitored. The methods for MeHg determination are not simple and straightforward, and until recently, have not been readily available in many countries. However, especially in biological samples, it is important to determine methylmercury, compared to total mercury alone, as a constant ratio of MeHg to total Hg cannot be assumed, and because MeHg is the more toxic form. The methods utilized by the participants for MeHg determination varied due to availability of instrumentation, and range from volatilization
In Environmental Biomonitoring; Subramanian, K., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1997.
ENVIRONMENTAL BIOMONITORING
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followed by detection by NAA (7) to ion exchange-CVAAS (8) to distillation coupled with gas chromatography (9). The results from the individual studies showed that, in most of the groups, the mercury resultsfromthe hair samples in the study populations were lower than 6 mg/kg, which has been proposed as a guideline level (2JO). This level has been extrapolated from the Provisional Tolerable Weekly Intake (PTWI) of 0.3 mg mercury (or
