Lead exposure in young school children in South African subsistence fishing communities
Introduction
The human toxicity of lead is well established. Studies over several decades, and in a variety of settings, have shown associations between elevated blood lead concentrations and reductions in intelligence scores, hearing loss, hyperactivity, shortened concentration spans and poor school performance in children, as well as lowered lifetime earnings (Tong et al., 2000). Relatively recent studies have also pointed to links between lead exposure and aggression or violent behaviour (Needleman et al., 2002, Needleman et al., 1996, Nevin, 2007). The growing global body of research illustrating the detrimental health and social effects of lead, as well as the lack of a threshold of safety, have prompted the consideration of lower blood lead action or guideline levels by international health bodies and governments (Betts, 2012, Gilbert and Weiss, 2006). Recently for example, it was recommended to the Centers for Disease Control (CDC) in the United States of America, that the current level of concern of 10 µg/dl be replaced with a reference range established as the 97.5th percentile of the blood lead distribution in that country. Currently that level equals 5 µg/dl, but may be changed following reviews expected to take place at four-yearly intervals (Betts, 2012).
African children have been identified as a group at particular risk of poisoning from exposure, often simultaneously, to multiple sources of lead (Nriagu et al., 1996). Two recent incidents of large scale lead poisoning in Zamfara, Nigeria (Lo et al., 2012) and Dakar, Senegal (Haefliger et al., 2009) have brought the vulnerability of African children to lead poisoning into sharp focus. Despite this, few, if any, African countries have comprehensive lead poisoning prevention or research/surveillance programmes in place, and the paucity of data or information in this regard has been highlighted (Tong et al., 2000). Instead, what is known about the sources and pathways of lead exposure in African children is derived mainly from ad hoc studies undertaken in a relatively small number of sites. For example, papers published on lead exposure from gasoline, paint (Mathee et al., 2007, Montgomery and Mathee, 2005), landfill sites (Graber et al., 2010), lead mining in the informal (Dooyema et al., 2012) and formal (von Schirnding et al., 2003) sectors, and the dismantling of batteries (Haefliger et al., 2009) have all highlighted the high degree of risk of lead poisoning in African children.
There is a particular dearth of published studies regarding lead exposure in subsistence fishing communities in Africa, as well as elsewhere in the world. One of only a handful of studies reported was undertaken in the Chuuk islands of Micronesia. In 256 children blood lead levels ranged from 1 to 37 µg/dl, with the mean level equalling 4 µg/dl. Amongst other risk factors, elevated blood lead levels were significantly associated with having a family member who made fishing weights; children with elevated blood lead levels were more than three times more likely to have a family member who made fishing weights. Elevated blood lead levels in the adults studied were also associated with making fishing weights. The authors concluded that making lead fishing weights was a significant source of lead exposure in adults and children in Chuuk islands (Brown et al., 2005). A blood lead survey undertaken among children aged 5 to 9 years in the coastal town of Cartagena, Colombia, showed that in 189 subjects blood lead levels ranged from 1 to 21 µg/dl, with the mean level equalling 5.5±0.23 μg/dl. Just over 7% of children had blood lead levels ≥10 μg/dl. Amongst other risk factors, elevated blood lead levels were associated with the production of fishing sinkers (Olivero-Verbel et al., 2007). Although reports of ingestion of fishing sinkers are rare, one such case of an 8-year old boy has been published in the literature. The boy was discovered to have pica, and had ingested around 25 lead fishing sinkers (Mowad et al., 1998).
Given its position at the southern tip of the African continent, South Africa is bordered by both the Atlantic and Indian Oceans, and has more than 2500 km of coastline. Relative to the rest of the African continent, South Africa has a high coastal population density, with subsistence and recreational fishing being important sources of income and recreation, respectively. Subsistence fishing communities along the South African coastline are widely characterized by high levels of poverty and economic hardship. Prompted by several anecdotal reports, a study was undertaken in two fishing villages along the South African coast in March 2012 to assess the prevalence of lead melting practices, the extent of childhood lead exposure and the associated risk factors. This paper describes the study findings.
Section snippets
Methods
Cross-sectional, analytical studies were undertaken at primary schools in March 2012 in the fishing villages of Struis Bay and Elands Bay—located along the southern (Indian Ocean) and western (Atlantic Ocean) coasts of South Africa, respectively. The villages were selected because of their known, substantial subsistence fishing communities. Children in grades 0, 1 and 2 in the local primary school were included in the study, after obtaining prior, written, informed consent from their parents or
Sample profile
A total of 160 children from impoverished communities in the Western Cape fishing villages of Struis Bay (n=81) and Elands Bay (n=79) were studied. The ages of the children, who were in grades 0 (27%), 1 (41%) and 2 (32%), ranged from 6 to 14 years, with the mean age equalling 7.5 years. Fifty two percent of the sample was male, and the predominant home language was Afrikaans (85%). The remainder of the sample spoke mainly Xhosa (11%), English (3%) and 1% lacked information on language.
Discussion
This study provides evidence of widespread use of lead in some South African subsistence fishing communities. Lead is melted by adults, often in the presence of children, and sometimes children themselves melt lead, for use in fishing activities or to play with. Mouthing, as well as unintentional ingestion of lead sinkers was reported, as were burn injuries from contact with molten lead. South African subsistence fishing communities may thus be exposed to lead vapour, as well as lead-laden dust
Funding sources
Funding for this work was provided by the South African Medical Research Council.
The protocol for this study was reviewed by Human Research Ethics Committee of the University of the Witwatersrand—the certificate of approval is available.
Acknowledgments
This work was funded by the South African Medical Research Council. The assistance of Mirriam Mogotsi with the logistical planning and fieldwork for the study is gratefully acknowledged.
References (22)
Lead exposure in indigenous communities of the Amazon basin, Peru.
Int. J. Hyg. Environ. Health
(2011)Blood lead levels and risk factors for lead poisoning in children and caregivers in Chuuk State, Micronesia
Int. J. Hyg. Environ. Health
(2005)- et al.
A rationale for lowering the blood lead action level from 10 to 2 µg/dl
Neurotoxicology
(2006) Reductions in blood lead levels among school children following the introduction of unleaded petrol in South Africa
Environ. Res.
(2006)- et al.
A preliminary study of residential paint lead concentrations in Johannesburg
Environ. Res.
(2005) Bone lead levels in adjudicated delinquents. A case control study
Neurotoxicol. Teratol.
(2002)Understanding international crime trends: the legacy of preschool lead exposure
Environ. Res.
(2007)Childhood lead poisoning in Africa: a growing public health problem
Sci. Total Environ.
(1996)Blood lead levels in children aged 5–9 years living in Cartagena, Colombia
Sci. Total Environ.
(2007)Yearly measurements of blood lead in Swedish children since 1978: the declining trend continues in the petrol-lead-free period 1995–2007
Environ. Res.
(2008)