Health risk assessment for people in Ronphibun district, Nakhon Si Thammarat province from exposure to arsenic

Abstract

The purposes of the study were to determine the amount of soil ingested by Thai people and to conduct a risk assessment of people residing in Ronphibun district from consuming the arsenic contaminated food by duplicate meal method and soil ingestion pathway. Soil ingestions in Thai people were studied in both children and adults by using aluminum (Al), silicon (Si), and yttrium (Y) as trace elements. A mass balance approach was employed to assess daily soil ingestion. Duplicate samples of foods and beverages, feces, and urine were collected for 7 consecutive days. The amounts of tracer elements in samples were analyzed using inductively coupled plasma-atomic emission spectrometry (ICP-AES). In children, an average and the 95th percentile of soil ingestion based on Al were 29.88 and 190.94 mg/d, based on Si were 36.33 and 173.35 mg/d, and based on Y were 30.05 and 157.38 mg/d (n = 70). In adults, the average and the 95th percentile of soil ingestion based on Al were 27.16 and 106.7 mg/d, based on Si were 22.53 and 127.39 mg/d, and based on Y were 23.47 and 114.77 mg/d (n = 70). The recommended mean and the upper percentile of soil ingestion for Thai children were 50 and 175 mg/d and Thai adults were 35 and 120 mg/d, respectively. Both point and probabilistic risk assessment were used to estimate risk of ingested arsenic from soil in Ronphibun. Soil samples were taken from a land located in area and determined of arsenic concentration by hydride generation-atomic absorption spectrometry (HG-AAS) (n = 59). Hazard quotients were 0.32 - 5.46 in children and 0.38 – 9.0 in adults. The ranges of cancer risk from exposed to arsenic in soil were 4.14 x 10-6 - 1.4 x 10-4 in children and 1.25 x 10-5 - 3.7 x 10-4 in adults. Exposure to arsenic from food and water in adults was investigated by using 7 consecutive days duplicate meal samples collection from Ronphibun residents (n = 112). Inorganic arsenic concentrations are determined by HG-AAS. The ranges of total cancer risk were 7.25 x 10-4 - 3.97 x 10-3. Hazard index ranged from 3.16 – 13.24. The averages of contributions to risk from and soil pathway were found to be 88% and 12%, respectively. Sensitivity analysis indicated that most influential of risk were exposure duration and arsenic concentration in meal. In conclusion, risk values for people in Ronphibun district from exposure to arsenic exceeded the risk level of concern.