Human health risk assessment of cadmium exposure through rice consumption in Mae Tao, Mae Sot District, Tak province

Mae Tao sub-district is located in the Mae Tao watershed, an important Cd contaminated area in Thailand. This study was conducted to i) investigate total Cd concentration in rice from households in the Mae Tao sub-district and ii) estimate health risks from Cd exposure through rice consumption. A total number of 159 rice samples were collected from households in all 6 villages of the Mae Tao sub-district. These rice samples were digested with concentrated nitric acid and analyzed by the inductively coupled plasma mass spectrometry (ICP-MS). Biodata information and rice consumption behavior were surveyed from the local residents at the same time of rice sample collection to estimate health risks. The results found that the average total Cd concentration in all rice samples (0.2843 mg kg-1) were within the CODEX maximum standard for Cd in rice (0.4 mg kg-1). However, about 19.5% of all rice samples had Cd concentration exceeded the CODEX maximum standard for Cd in rice. There were no significant difference in total Cd concentration between white jasmine rice and sticky rice (p>0.05). However, locally grown rice usually contained higher total Cd concentration than the purchased rice by 1.48 times. When compare the total Cd concentration in each village, the average total Cd concentrations in rice samples from Mae Tao Klang (village No.2) (0.4151 mg kg-1) and Mae Tao San Rongrian (village No.4) (0.5097 mg kg-1) exceeded the CODEX maximum standard by about 1.04 and 1.27 times, respectively. The Cd exposure from the only sticky rice consumption pattern was the highest (2.26 × 10-3 mg kg-1 day-1), followed by both types of rice consumption pattern (1.39 × 10-3 mg kg-1 day-1) and the only white jasmine rice consumption pattern (6.30 × 10-4 mg kg-1 day-1). The Cd exposure in each rice consumption pattern was mainly influenced by the total Cd concentration in rice and the ingestion rate of the local residents. According to the health risk assessment between different rice consumption patterns, the average HQ value of the only sticky rice consumption pattern was the highest (2.2633), followed by both types of rice consumption pattern (1.3870) and the only sticky rice consumption pattern (0.6303). The overall results indicate that the local residents who consumed only sticky rice and both types of rice on a daily basis could experience non-carcinogenic health impacts from Cd exposure through rice consumption.