During the month of September-October 1997, a depression storm caused massive flooding in the area of western Kanchanaburi province, Thailand, causing lead-contaminated water from a nearby lead refinery plant to spill into the surrounding areas of Clitty Creek; exposing the village downstream to large amounts of lead. The Ministry of Public Health, together with the Ministry of Science, the Ministry of Industry, and officials from the Kanchanaburi Office of Public Health, began measures for environmental deleading and assessment of exposure and health risks of the population.
This was a retrospective cohort study of the effects that environmental remediation and chelation therapy had on the blood lead levels of children residing in Lower Clitty Creek Village during the period between 1997-2001. Sixty-eight children were followed yearly for their blood lead levels and hematocrit, beginning in early 1998. Simultaneously, programs for environmental remediation had begun. The blood lead levels (BLLs) of children were followed over a 3-year period. The BLLs during the 2 year period of environmental remediation alone were compared. Subsequently, when chelation therapy was instituted, levels pre and post chelation therapy, as well as the efficacy of the two different chelation methods were compared using standard 2-tailed t-test.
The initial average BLL was 27.75 +/- 5.4 mg/dl (1998). After environmental remediation began, BLL at one year (1999) was 30.64 +/- 4.49 mg/dl (p = 0.072), and at two years (2000) was 30.30 +/- 5.1 mg/dl (p = 0.537). There were 18 children with BLLs > 25 who were elected to receive chelation therapy with CaNa2EDTA (11) and DMSA (7). Post chelation average BLL was 18.73 +/- 7.50 mg/dl. The difference between pre and post chelation BLL was statistically significant (p < 0.001: paired t-test). The differences in average BLLs between pre and post chelation for the EDTA group was 15.37 mg/dl and for the DMSA group it was 8.91 mg/dl. Children treated with EDTA appeared, on average, to have 6.47 mg/dl (p < 0.05: 95% CI (0.821-12.12)) lower BLL than those treated with DMSA.
The incident at Clitty Creek serves to illustrate the importance of environmental remediation as a priority to treating lead poisoning in children. Only when effective environmental deleading has taken place can medical intervention in the form of chelation therapy begin.