Factors associated with elevated blood lead levels in first grade school children in Cape Town, South Africa
Date
2013-01-25
Authors
Aliraki, Lisbon
Journal Title
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Abstract
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.