CORRESPONDENCE

Trends in lead exposure in a rural mining town in South Africa, 1991 - 2008

To the Editor: Lead exposure through mining processes contributes significantly to environmental and human contamination world-wide.^[1-3] Studies have shown that there is no safe level of exposure, and very low levels (blood lead levels <5 μg/dL) have resulted in neurocognitive and behavioural abnormalities in children.^[4] This has detrimental economic and social consequences, especially in low- and middle-income countries where resources to mitigate the effects of lead exposure are limited.^[5] In 1991, 2002 and 2008, cross-sectional surveys assessing lead exposure were conducted in grade 1 children in a remote lead-mining town (Aggeneys) and a control town (Pella) about 40 km away in the Northern Cape Province, South Africa (SA). Blood lead levels (BLLs) were assessed in whole-blood samples using atomic absorption spectrophotometry in 1991 and 2002 and in capillary blood using the LeadCare 1 analyser system in 2008.^[6,7]

The sociodemographic profiles of the study children remained similar from 1991 to 2008 (Table 1). Socioeconomic status was higher in Aggeneys than in Pella. However, despite the higher socioeconomic status in Aggeneys, the grade 1 children's mean BLLs were significantly elevated in all three surveys. Between 1991 and 2002 the mean BLL dropped by approximately 50%, but did not fall significantly thereafter. The initial decline between 1991 and 2002 may have been due to the phasing out of leaded petrol from 1996, since declines in BLLs were observed in both Pella and Aggeneys. However, in Pella the proportion of children with BLLs >5 μg/dL dropped from 52% in 2002 to 16% in 2008. In Aggeneys, the proportion with BLLs >5 μg/dL decreased by only 8% and the proportion of children with BLLs >10 μg/dL increased by 9%, indicating ongoing lead exposure in the mining town community.

In higher-income countries, significant decreases in the risk of lead exposure in mining communities have occurred. In the USA, interventions in the Bunker Hill mining community resulted in a drop in children with BLLs >10 μg/dL from 48% in 1988 to 3% in 2001.^[8] Programmes such as environmental decontamination, including soil treatment, appropriate worker and domestic hygiene measures, and community education and support, as well as continued screening of children's BLLs, have resulted in a significant reduction in exposure in this site. However, similar measures have seldom been implemented to the same extent in poorer countries. This series of surveys, conducted over a period of 17 years in an SA lead-mining town, indicates an elevated and enduring (73% of children had BLLs >5 μg/dL), yet avoidable, risk of exposure to lead.

Nisha Naicker

Medical Research Council of South Africa Environment and Health Research Unit, Johannesburg, South Africa, and School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg nisha.naicker@gmail.com

Angela Mathee

Medical Research Council of South Africa Environment and Health Research Unit, Johannesburg, South Africa, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, and Faculty of Health Sciences, University of Johannesburg (Doornfontein Campus)

References

1. Van Green A, Bravo C, Gil V, Sherpa S, Jack D. Lead exposure from soil in Peruvian mining towns: A national assessment supported by two contrasting examples. Bull World Health Organ 2012; 90(12):878-886. [http://dx.doi.org/10.2471/BLT.12.106419]        [ Links ]

2. Moreno ME, Acosta-Saavedra LC, Meza-Figuera D, et al. Biomonitoring of metal in children living in a mine tailings zone in Southern Mexico: A pilot study. Int J Hyg Environ Health 2010;213(4):252-258. [http://dx.doi.org/10.1016/j.ijheh.2010.03.005]        [ Links ]

3. Paoliello MMB, de Capitani EM, Goncalves da Cunha F, et al. Exposure of children to lead and cadmium from a mining area of Brazil. Environ Res 2002;88(2):120-128. [http://dx.doi.org/10.1006/enrs.2001.4311]        [ Links ]

4. Canfield RC, Henderson CR, Cory-Slechta DA, Cox C, Jusko TA, Lanphear BP. Intellectual impairment in children with blood lead concentrations below 10 μg/dl. N Engl J Med 2003;348 (16):1517-1526. [http://dx.doi.org/10.1056/NEJMoa022848]        [ Links ]

5. Attina TM, Trasande L. Economic costs of childhood lead exposure in low- and middle-income countries. Environ Health Perspect 2013;121(9):1097-1102. [http://dx.doi.org/10.1289/ehp.1206424]        [ Links ]

6. Von Schirnding Y, Mathee A, Kibel M, Robertson P, Strass N, Blignaut R. A study of pediatric blood lead levels in a lead mining area in South Africa. Environ Res 2003;93(3):259-263. [http://dx.doi.org/10.1016/S0013-9351(03)00117-8]        [ Links ]

7. Rollin HB, Mathee A, Levin J, Theodorou P, Tassel H, Naik I. Examining the association between blood manganese and lead levels in schoolchildren in four selected regions in South Africa. Environ Res 2007;103(2):160-167. [http://dx.doi.org/10.1016/j.envres.2006.08.011]        [ Links ]

8. Von Lindern I, Spalinger S, Petroysan V, von Braun M. Assessing remedial effectiveness through the blood lead:soil/dust lead relationship at the Bunker Hill Superfund Site in the Silver Valley of Idaho. Sci Total Environ 2003;303(1-2):139-170. [http://dx.doi.org/10.1016/S0048-9697(02)00352-2]        [ Links ]