Lead poisoning is the most important pollution in children which affects the developing brain and IQ. Previous studies of blood lead levels in Thai children were all higher than 10 microg/dl.
To identify risk factors and impacts associated with high lead levels (>10 microg/dl) in Bangkok children
The longitudinal study (n = 84) followed blood lead levels of a birth cohort, 6, 12, 18, 24 and 72 months of age from 1993 to 1999. Multiple cross-sectional studies (1992-1996) comprising children under 15 years of age attending the outpatient clinic, Ramathibodi Hospital (n = 511), kindergartens (n = 60), 6 primary school students (n = 564) and secondary school students (n = 377) in Bangkok, were recruited. Blood lead levels were assessed by atomic absorption spectrometry. Questionnaires to identify risk factors were completed by parents of under 2-year-old children and primary school students. IQ was assessed in the longitudinal group at 2 years of age and in primary students.
The mean blood lead levels (microg/dl) were 5.57 +/- 2.31 at birth, 5.03 +/- 2.21 at 6 years of age in a cohort study, 6.74 +/- 2.02 in kindergartens, 9.26 +/- 3.68 in primary students and 9.03 +/- 3.65 in secondary school students. The proportion of high blood lead increased with age from 1 per cent at birth to 35 per cent in secondary school students. In the kindergartens and secondary school, males had higher lead levels than females. In the primary school study, the significant risk factors (Odd Ratio-OR) of high lead level were; living in Bangkok (6.18), male (1.67), maternal labour workers (1.79), family income lower than 3,000 baht/month (2.24), a crowded family with more than 9 members (2.22), household members whose present occupation was related to printing (4.55) or lead smelting previously (4.85). Children in the high lead group had lower weight (p = 0.0000) and height (p = 0.0000) and were slow learners determined by their teachers (p = 0.0332).
The blood lead levels in Bangkok children were not high and have tended to decrease following the reduction of air lead levels because of unleaded gasoline usage. A periodic surveillance survey is still necessary to monitor blood lead level in Bangkok children especially among those with risk factors.