Evaluation of sub-clinical lead poisoning of young children in Hong Kong

Abstract

Community based screening of childhood lead poisoning was conducted from April 2000 to May 2001 by convenience sampling from the pool of participants in the Telehealth project. Aims were to determine the extent of sub-clinical childhood lead poisoning in the community and whether risk factors for lead (Pb) exposure can be identified for early anticipatory guidance on lead prevention. Fifty-one boys (mean age 6.45 +-2.30) and 50 girls (mean age 7.09+-2.34) were included in this study. Their parents were interviewed based on a lead exposure risk assessment questionnaire. Measurements of lead of capillary blood (PbB) and occipital hair (PbH) samples by Graphite Furnace Atomic Absorption Spectrometer were then correlated to the risk factors identified from the questionnaire. The mean of PbH was 3.69+-5.4ug/g, while the mean of PbB was 6.52+-5.0 ug/dL. About 18.2% (n=55) of PbB results were elevated (above the action level of 10 ug/dL), while 6.2% (n=97) of participants had PbH above the harmful level of 11 ug/g. The Pearson Correlation of PbB and PbH was significant, r=0.495 (p=0.00, n=51), where linear regression model was formulated. Therefore, non-invasive collection of hair samples for analysis can be an indicative method of screening childhood lead poisoning. The two demographic factors associated with elevated PbB level are lowered economic status and for age below 6. The main preventable risk factors that contributed to a higher lead level include mouthing activity (putting things in mouth or biting fingers), lack of hand washing, and insufficient dietary calcium intake. The risks of environmental factors include exposure to peeling paint chips and second hand cigarette smoke from household member were significantly correlated to PbH level. None of the symptoms noted from parents' self report were significantly related to PbH and PbB levels as no overt symptoms are expected at such sub-clinical level. Symptoms of short attention span with irritability were the most common observations noted from parents' self report for those children with elevated body lead load. Promoter activity of increased intake of calcium rich food and proper hand washing, along with inhibiting mouthing activity and second hand smoke exposure are vital to reduce lead exposure and absorption by children. Such recommendations are incorporated into the childhood lead poisoning prevention program including a website to promote public awareness.