Cadmium-exposed population in Mae Sot District, Tak Province: 1. Prevalence of high urinary cadmium levels in the adults.

BACKGROUND: In Mae Sot District, Tak Province, Thailand, the paddy fields receiving irrigation from the two creeks and crops grown in the areas were found to contain markedly elevated cadmium levels during the surveys in 2001-2004. OBJECTIVE: The present report carried out a survey in 2004 to determine urinary cadmium, a good index of excessive cadmium exposure and body burden, among the exposed residents aged 15 years and older in these contaminated areas. MATERIAL AND METHOD: Morning urine samples were collected from the subjects and then kept frozen until cadmium analysis. Urinary cadmium was determined using the atomic absorption spectrometry and urinary creatinine was determined using a method of reaction with picric acid at alkaline pH and colorimetry. RESULTS: Of the 7,697 persons surveyed, only 45.6% had urinary cadmium levels < 2 microg/g creatinine. About 4.9% were between 5 and 10 microg/g creatinine and 2.3% had cadmium concentrations > 10. The urinary cadmium level was greater among women than men and increased with increasing age. Smokers were more likely to have high urinary cadmium than non-smokers. Persons who mainly consumed rice grown locally in the contaminated areas had higher urinary cadmium than those who did not. CONCLUSION: Persons who had high urinary cadmium levels and might have cadmium-induced toxic effects should be screened for early detection of chronic cadmium toxicity. Smoking cessation programs should be one component of preventive action beneficial for the study population. The production of rice and other crops for human consumption should be prohibited to prevent further accumulation of cadmium in the body of the exposed population.

Predictors of elevated blood lead level in Thai children: a pilot study using risk assessment questionnaire.

INTRODUCTION: In the era post leaded-gasoline use, the risk of exposure to environmental lead in Thai children is not well described. This is a pilot study using a risk assessment questionnaire to identify children with elevated blood lead level. MATERIAL AND METHOD: Children from 4 communities, 2 in the Bangkok metropolitan area and 2 in Kanchanaburi province, were recruited during their well child visits. Blood lead levels were obtained in all children and parents are asked to fill out a 25-item risk assessment questionnaire. STATISTICAL ANALYSIS: The relationship between the blood lead level and dependent variables were tested using linear regression and one-way analysis of variance (ANOVA) as appropriate. RESULTS: There were 296 children included in the study; 33 from Klong Toey and 114 from Siriraj community in Bangkok while 149 were from two different communities in Kanchanaburi province. The average blood lead level was 5.65 +/- 3.05 mcg/dL. The overall prevalence of children with blood lead level > 10 mcg/dL was 8.1%, while that of the Klong Toey community was 12.5%. The questionnaire identified 3 independent predictors of elevated blood lead levels; the presence of peeling paint in or outside the house, eating paints chips, and the geographic location of children. CONCLUSION: Using a risk assessment questionnaire, together with obtaining blood lead level has proven effective in identifying key environmental features associated with elevated blood lead level in children from sampled Thai communities. The challenge now is to conduct a larger epidemiological study of a similar type in order to guide the screening and preventive efforts.

The management of environmental lead exposure in the pediatric population: lessons from Clitty Creek, Thailand.

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. METHOD: 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. RESULTS: 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. CONCLUSION: 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.