Lead neurotoxicity and socioeconomic status: Conceptual and analytical issues

Abstract

Socioeconomic status (SES) is usually considered to be a potential confounder of the association between lead exposure and children's neurodevelopment, but experimental and epidemiological data suggest that SES might also modify lead neurotoxicity. The basis of this effect modification is uncertain, but might include differences among SES strata in co-exposures to other neurotoxicants, genetic susceptibilities, environmental enrichment, and stress. The role of SES in the causal nexus is likely to include other dimensions, however. It conveys information about lead exposure opportunities as well as about predictors of child outcome that are correlated with but causally independent of lead. Failure to distinguish these aspects of SES will lead to an underestimate of lead's contribution, and might even result in attributing to SES health effects that should be attributed to lead. Conventional models, which treat SES and SES-related factors solely as potential confounders, do not capture the possibility that a child's early lead exposure alters the behaviors that the child elicits from others. Failure to model lead's contribution to such time-varying covariates will also tend to bias estimates of lead neurotoxicity toward the null. On a transgenerational level, low SES might be a proxy for vulnerability to lead. To estimate the burden of lead-associated neurotoxicity on a population level, we need to apply analytical approaches that model a child's development and its context as a complex system of interdependent relationships that change over time.Socioeconomic status (SES) has played a central role in efforts to characterize the magnitude of the risk that lead poses to children. Because exposure is often greater among children of low SES (Baghurst et al., 1999) and low SES is a powerful predictor of neurodevelopment (Tong et al., 2007), it has long been recognized that due consideration must be given to the possibility that any observed association between lead exposure and neurodevelopment is, in part, an artifact of residual confounding, and thus reflects a Type I error of inference. Indeed, adjusting for SES and related covariates can result in reductions of 50% or more in the magnitude of lead's regression coefficient (e.g., Bellinger et al., 1992). Whether an investigator adequately handled this issue, avoiding a Type I error of inference, became one of the central determinants of whether the inferences drawn from a lead study were viewed as credible.The role of SES in lead studies is likely to be much more complex than that of solely a confounder, however. Two dimensions of this issue are discussed in this paper. The first section summarizes epidemiologic and experimental findings suggesting that SES and SES-related aspects of a child's social environment modify the neurotoxicity of lead such that children of

Lead exposure among the general population of Duhok governorate, Kurdistan region, Iraq

“…Exposure to low doses of lead is particularly harmful to children, whose neurological development may be persistently and irreversibly affected [1][2][3]. Exposure to lead causes a number of diseases in later age groups, including mild mental retardation, as shown by loss of IQ points, as well as increased blood pressure, anaemia and gastrointestinal effects.…”

Adsorption of Pb(II) on Spent Leaves of Green and Black Tea

“…Lead (Pb), in particular, is one of the most common environmental contaminants due to its wide use in petroleum, mining, paint and pigments, ceramics and weapons industries. Its accumulation in the body may cause several pathological states, including brain damage, kidney failure and serious developmental, learning and behavioral problems in children (Needleman, 2004;Bellinger, 2008;Rowland and McKinstry, 2006). In addition, toxicity has been shown to occur at concentrations as low as 1 pM (Markovac and Goldstein, 1988;Johnston and Goldstein, 1998).…”

Intake of the First-Generation Anti-Histamines in Early Childhood May Have an Adverse Effect on Cognitive Function. Population Based Pharmacoepidemiologic Study in Non-Asthamtic Children

“…Moreover, studies carried out by Bellinger [21] suggest that social context also modifies the effects of chemical neurotoxins. For example, material hardship has been demonstrated to modify the neurotoxic effects of tobacco smoke in children in the study done by Rauh et al [22].…”