A research report submitted to the Faculty of Health Sciences, University of Witwatersrand, South Africa in partial fulfilment of the requirements for the Master of Medicine in the branch of Community Health Johannesburg, 2014 / BACKGROUND: Lead is one of the most widely used and studied heavy metals. Lead has a number of serious detrimental effects including those related to the nervous system (seizures, ataxia) heamotological system (anaemia) and renal system. The severity and prognosis of diseases related to lead exposure is more pronounced in children, even with very low blood levels. Anecdotal reports of lead melting to make fishing sinkers in South African subsistence fishing communities prompted the conduct of an epidemiological study in four South African fishing villages to investigate the extent of lead melting and the associated risks in children. METHODS: A cross sectional analytical study was conducted. The study was conducted in two schools located along the western (Atlantic Ocean) coast of South Africa (HP Williams Primere in Stompneusbaai and NGK Primary School in Elands Bay) and in two schools located along the southern (Indian Ocean) coast of South Africa Bertie Barnard School in Stilbaai, Struisbaai Primere School in Struisbaai. Blood samples were collected for lead content analysis, and anthropometric measurements were taken. Questionnaires were administered to obtain information about socio-economic status and risk factors for lead exposure. A total of 196 children from grade 0, 1 and 2 were included in the study. RESULTS: Blood lead levels in the sample ranged from 1.9 to 22.4 μg/dl. Central tendency of the blood lead level demonstrated an arithmetic mean of 6.87 μg/dl (95% CI: 6.36 to 7.37 μg/dl) and a median of 6.1 μg/dl. More than half of the children in the study had blood lead levels between 5.0 - 9.9 μg/dl, whilst 13% that had levels higher than 10 μg/dl. Age, sex and ethnicity was not significantly associated with high blood lead levels whilst, lead melting practices and interaction of children with pets were strongly associated with high blood lead levels in children. Multivariate analysis showed that the presence of a fisherman in the household and children watching smelting were significantly associated with higher blood lead levels. Village remained a confounding variable in the model. CONCLUSIONS: This study is the first report on blood lead levels in fishing villages on the African continent and provides evidence that lead is still used widely as the primary substance used to make fishing sinkers. The prevalence of plumbism was high at 75%. Policy and awareness is needed to address this neglected public health concern.

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Introduction: Lead metal toxicity in children is a major public concern internationally. In South Africa, January 2006 was the date set for the complete phase-out of leaded petrol, a well known major source of environmental lead contamination. Analysis was conducted to describe the distribution of blood in children, to establish proportions of children with elevated blood lead levels (unacceptable blood lead levels of ≥ 10 μg/dl) and to establish factors associated with elevated blood lead levels using data collected in 2007, one year after the phase-out of leaded petrol. Methods and Materials: An analytical cross-sectional secondary data analysis was conducted on a survey dataset from the Environment and Health Research Unit of the Medical Research Council, South Africa. The primary sampling unit (cluster) was defined as primary schools. Data on first grade children from 13 schools from three suburbs of Cape Town – Woodstock (eight schools), Hout Bay (three schools) and Mitchell’s Plain (two schools) – were analyzed using a survey method, calculating design-based robust standard errors. Different weights were applied to schools in the suburbs which formed the stratification variable. The outcome variable was defined as blood lead levels < 10 μg/dl or ≥ 10 μg/dl. A number of background characteristics – health and diet, housing and social aspects – were investigated; odds ratio measurement was calculated and reported. Results: A total of 532 children were included in the analysis, representing a weighted total of 1 744 children. The children’s weighted mean age was 7.40 years (95% CI 7.39 to 7.41). The geometric weighted mean blood lead level was 5.27 μg/dl (95% CI 5.08 to 5.46). The weighted proportion of children with BLLs ≥ 10 μg/dl was 11.81% (95% CI 8.78 to 15.72); in Woodstock it was (21.0%). In the multivariable logistic regression, several factors were independently associated with higher odds of having BLLs ≥ 10 μg/dl, including use of gas for cooking OR 3.24 (95% CI 2.34 to 4.48) p <0.0001; houses in need of major repairs OR 7.81 (95% CI 1.59 to 38.33) p = 0.017; attending a crèche/preschool OR 15.23 95% CI (3.40 to 68.29) p = 0.003; Others included use of buses or taxis, which increased the odds of a child having a BLLs ≥ 10 μg/dl compared to walking to school by 5.20 times (95% CI 3.00 to 8.99) p < 0.0001 and children who were living in flats (OR 5.55, 95% CI 3.76 to 8.18, p < 0.0001) or in informal/shack dwellings (OR 2.09, 95% CI 1.06 to 4.12, p = 0.037) were at greater odds of having a blood lead ≥ 10 μg/dl than if they lived in free-standing houses. The following factors offered protection against elevated BLLs: Using private cars to transport children to school offered 0.83 lower odds of a child having elevated lead levels (OR 0.17, 95% CI 0.09 to 0.31, p < 0.0001) compared to walking to school, use of plastic water pipes OR 0.60 (95% CI 0.44 to 0.82) p = 0.005 and, domestic cleaning practices, such as cleaning floors with a wet mop (rather than a dry broom) reduced the odds of having blood lead levels ≥ 10 μg/dl by 0.88 (OR 0.12, 95% CI 0.10 to 0.15, p < 0.0001). Conclusion and Discussion: This analysis indicated that the distribution of blood lead appears similar that determined in the leaded petrol era. The proportion of children with elevated blood lead levels in a Cape Town study was still high. Multiple factors were associated with BLLs ≥ 10 μg/dl. Some factors were protective. The implementation of the phasing out of the leaded petrol should be critically monitored to determine the time period before observing a reductive effect. Preventive measures targeting removal of non petrol sources of lead from the school and home environments should be considered as important.

Thesis (M.S.)--Ball State University, 2009. / Title from PDF t.p. (viewed on June 08, 2010). Includes bibliographical references (p. [70]-71).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 364-384.

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Introduction Lead exposure continues to be a major public health issue in South Africa, and other low and middle income countries. Environmental lead exposure has been associated with detrimental health effects in children. The aim of this thesis was to assess the prevalence of lead exposure and its association with various risk factors, its effects on puberty and socio-behavioural adjustment in adolescents. Methods The Birth to Twenty (Bt20) cohort study started in 1990, and is a long-term prospective follow-up study of children’s health and well-being. Mothers were recruited from antenatal clinics in the Johannesburg-Soweto metropolitan area between April and June 1990 (n=3273). Lead levels were analysed in samples of cord blood collected at birth (n=618) and whole venous blood collected at 13 years of age (n=1546). Data on selected child, maternal and household factors were collected using a structured questionnaire in the third trimester of pregnancy and at 13 years of age. Additional data on puberty (attainment of menarche and self-reported Tanner staging for breast and pubic development) and behaviour using the Youth Self Report was obtained at 13 years of age. Results In the Bt20 cohort the mean blood lead level at birth was 5.9 μg/dl, and at 13 years of age it was 5.7 μg/dl. The majority of children had blood lead levels above 5.0 μg/dl (52% at birth and 56% at 13 years). At birth, being a teenage mother and having low educational status were strong predictors for elevated cord blood lead levels. Being a male child, having an elevated cord blood level, and lack of household ownership of a phone were significant risk factors for high blood lead levels at 13 years. In 13 year old females with pubertal data (n= 682) the mean blood lead level was 4.9 μg/dl. Fifty percent had blood lead levels < 5.0 μg/dl, 49 % were ≥5.0 μg/dl and 1% was > 10.0 μg/dl. The average age of menarche was 12.7 years. At 13 years, 4% and 7% had reached Tanner stage 5 for pubic hair and breast development, respectively. Analyses showed that higher blood lead levels were significantly associated with delays in all measures of puberty (p <0.001). In the 13 year old sample with data on the Youth Self Report (n= 1041), the geometric mean blood lead level was significantly (P value<0.001) higher in boys (6.0 μg/dl) compared to girls (4.5 μg/dl). The bivariate analyses stratified by gender showed that boys’ blood lead levels were significantly associated with four types of aggressive behaviour. There were no significant associations found in girls. A multivariate analysis was conducted in the sample of boys and after adjusting for socio-economic factors ”Attacking People” remained significantly associated with blood lead levels. Conclusion Significant associations found in the study point to the low socio-economic status of lead exposed children. These poor circumstances frequently persist into adolescence resulting in continued high lead levels. Higher blood lead levels were associated with a delay in the onset of puberty in girls, and with anti-social behaviour among boys in early adolescence. Lead exposure in low and middle countries is generally higher compared to high income countries, and thus the effects of high blood levels are much greater and have larger personal and public health significance.

Call number: LD2668 .T4 1978 M58 / Master of Science

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The effects of lead poisoning have been known for centuries and the deleterious effects of chronic, low to moderate levels of lead exposure on children's cognitive functioning is now well-established (Needleman & Gatsonis, 1990; Schwartz, 1995). Similarly, low and moderate levels of lead exposure early in life have been frequently associated with behavioural disturbances later in life in children and animals. However, few studies have systematically investigated the link between lead-induced deficits in cognitive functioning and lead-induced behavioural disturbances. This project describes a series of studies investigating the effects of lead on auditory processing and attentional behaviour, and their ability to account for the deleterious effects of lead on IQ in children participating in the Port Pirie Cohort study. Capillary blood samples were collected from the children at various ages from birth to 2 years, and annually thereafter until the age of 7. A measure of lifetime PbB was calculated for each child using the geometric mean of all the blood lead samples. This measure of lifetime PbB was used as a continuous explanatory variable in each of the studies described below. A variety of sociodemographic, health, anthropometric, birth and developmental covariates and potential confounders were recorded prospectively and concurrently. Using Needleman et al.'s (1996) analysis protocol, 8 of these covariates were included in all final regression models. Study One: A total of 387 children from Port Pirie, Australia (mean age of 7.7 years) participated in a study of children’s simple auditory processing. Children completed a series of monaural listening tasks across 4 ear/hand conditions. It was hypothesised that auditory reaction time and auditory processing accuracy would be related the lifetime PbB. Analysis revealed no significant associations between lifetime PbB and the reaction time to target words and a small significant association (3.6%) between lifetime PbB and accuracy of target word detection in just one of the four ear/hand conditions. The strongest associations were found between PbB and false responses to distractor words (10.1%, after adjusting for confounders). It was speculated that this pattern of results could be explained via lead effects on other processes such as impairments to impulse control or attentional processes. Study Two: Study Two investigated the effect of lifetime PbB on children’s complex auditory processing. In this study participants completed dichotic listening tasks across 4 different ear/hand conditions. After controlling for potential confounders, lifetime PbB accounted for 6.2% of the variance in the accuracy of target word detection. A weak direct association (3.0% of the adjusted variance) was also found between lifetime PbB and target word reaction time. No significant associations were found between lifetime PbB and the percentage of false responses or the speed of the false responses. Again the pattern of results was suggestive of a deficit in attentional processes such as freedom from distraction and impulse control. Study Three: This study hypothesised that lead-induced impairments to attentional behaviour - similar to those observed in Studies One and Two - would be observed in other contexts. The mothers of 492 cohort children, and teachers of 454 of the children participated in this study. The mean age of children for whom ratings were collected was 7 years and 4 months. Two versions of the Conner’s Behavior Rating Scale were used to rate the children’s behaviour: The Parent Rating Scale and the Teacher Rating Scale. Lifetime PbB accounted for a significant amount of the variance in Conner’s Parent Behavior Rating Scale scores. It accounted for 5.9% and 7.3% of the unadjusted variance in the Immature/Inattentive, and Hyperactive/Impulsive scores respectively. After adjusting for covariates, each of these associations remained significant. The associations between lifetime PbB and girls' behaviour scores were much higher (11.2%) than the PbB associations with boys' behaviour scores (4.6%). The unadjusted associations between lifetime PbB and Teacher Rating Scores, although much lower, were also significant and accounted for between 1.2% and 2.4% of the variance in the behaviour scores. However, after controlling for potential covariates these associations were no longer significant. These results indicated that increases in lifetime PbB were associated with higher Hyperactivity/Impulsivity and Immature/Inattention and scores on the Conner's Parent Rating Scale, but not the Conner's Teachers Rating Scale. Study Four: In this study it was hypothesised that a significant association would exist between children’s auditory processing performance and parent and teacher behavioural ratings of inattention and impulsivity. Correlational analysis was conducted on the data from Studies One, Two, and Three, to ascertain if the behavioural patterns as reported by the children's parents and teachers, were associated with the children's performance on the auditory processing tasks. Correlational analysis revealed highly significant correlation coefficients in the direction predicted between auditory processing scores and the Inattention and Hyperactivity/Impulsive scores of the Conner's Parent and Teacher Rating Scales. Study Five: The purpose of this study was to examine the extent to which auditory processing and attentional behaviour scores could account for the lead-induced deficits in children's global cognitive abilities. Combining IQ data with data from Studies One, Two, and Three, a hierarchical analysis was conducted with lifetime PbB as the continuous explanatory variable. The analysis entered potential covariates at step 1, behaviour ratings at step 2, auditory processing efficiency in step 3, auditory processing speed in step 4, and lifetime PbB at step 5. The results indicated that when parent and teacher ratings of behaviour and auditory processing efficiency were included in the model, lifetime PbB no longer accounted for a significant proportion of Verbal, Performance or Full-Scale IQ scores. On the other hand, further analyses demonstrated that the significant associations between lifetime PbB and parental behaviour ratings could not be accounted for by including IQ scores as mediating variables in the analytical model. Conclusion: The results of this project provide evidence for the deleterious effect of lead exposure on children's auditory processing performance and parent ratings of behaviour. Further, including these variables in an analysis of the effects of lifetime PbB on IQ served to markedly attenuate direct effect of lead on IQ to the level of non-significance. Taken together the data implicates disturbances to attentional processes (such as impulsivity and inattention) as possible mediators of lead-induced deficits in IQ.