[Health Risk Assessment of Microcystins from Drinking Water Source by Monte Carlo Simulation Method]

To investigate the microcystins(MCs:MC-RR, MC-LR and MC-YR) exposure from drinking water source and to assess the health risk using Monte Carlo simulation method. 90 samples randomly collected from five sample points set along the river were determined using the national standard method (GB/T 20466-2006) during the period of January to June 2016. Professional risk assessment software@Risk7.0 was used to evaluate the dietary intake (exposure) risk of MCs based on building a nonparametric probabilistic evaluation model. First, 90 samples with the MCs were collected for fitting of distribution and the optimal fitting distribution model was selected from the results of three statistical test methods:the Chi-Squared test, the Anderson-Darling test and the Kolmogorov-Smirnov test. Of the 90 water samples tested, the most frequently detectable MCs was MC-RR with the detectable rate of up to 51.11% within the content range of 0.0017-0.3863 μg·L^-1, followed by 47.78% of MC-LR within the range of 0.0285-0.2796 μg·L^-1, and 21.11% of MC-YR within 0.0030-0.1362 μg·L^-1. These results indicated that vast majority of MCs in testing samples were at relatively low levels with the highest concentration of MC-RR at 0.3863 μg·L^-1 and MC-YR concentration was the lowest from drinking water source. The fit distribution of MC-LR concentration was the ExtValueMin(0.11391, 0.098462) and that of MC-RR was Logistic(0.058064, 0.053044)(the first number was μ as the position parameter, the second number was σ as the scale parameter). The result indicated that health risks of MC-LR from drinking water source were higher than those of MC-RR and MCs pollution and would lead to high potential health risks especially for children. The health risks caused by the MC-LR from drinking water source for children were significantly higher than the maximum allowance levels recommended by USEPA(1×10^-4), and the health risks caused by the MC-LR from drinking water source for adults were significantly higher than the maximum allowance levels recommended by ICRP(5×10^-5). Therefore, it is necessary to strengthen the protection and monitoring of drinking water source for effective control of water pollution and protection of human health.