Human Health Risk Assessment Of Algae Bloom In Drinking Water Source

Algal blooms occurred in drinking water source is a threat to drinking water source safety and human health in China. It is the precondition of algae bloom emergency management to assess the human health risk reasonably. In order to protect human health, the risk of acute exposure to algae bloom water was evaluated by health risk assessment chemical model.The human health hazard chemicals are mainly Microcystins (MCs) and Disinfection By-Products (DBPs) in algae bloom polluted water. MCs are one kind of hepatic toxin, act on liver cells and liver macrophages, leading to human liver disease. The health hazards of DBPs are carcinogenicity and reproductive toxicity. Based on the method of acute exposure safety threshold, the acute safety thresholds of MCs and DBPs were calculated. The safety threshold of MC-LR, chloroform, Bromodichloromethane, bromoform, dichloroacetic acid, trichloroacetic acid are0.004,18,0.25,0.2,2,0.13,0.5mg/L, respectively.The pollution characteristics of MCs and DBPs in chlorination were investigated. The MC-LR concentration is0.11-3.89μg/L in chloride water. Linear correlation analysis of water quality index and MC-LR concentration were conducted. The correlation of MC-LR and Chl-a, TP, NH3-N are positive, R2are0.85,0.81and0.75, respectively. The correlation of MC-LR with N/P is negative correlation. By the Resin adsorption method, the DOM fractions were characterized. The results show that HIS is the mainly fraction in raw water. chloroform, bromodichloromethane, dibromochlomethane, bromoform chloroactic acid, dichloroacetic acid and trichloroacetic acid are detected in chloride water. Other DBPs species are observed some time. The vary concentration range of chloroform, bromodichloromethane, dibromochlomethane, bromoform, chloroactic acid, dichloroacetic acid and trichloroacetic acid are:1.85～52.5,1.31～183.25,1.32～194.35,0.19～15.83,0.22～118.6,0.15-85.3and1.05～28.46μg/L, respectively. The correlation analysis between water quality index and DBPs yields shows that HAAs is highly correlated with the concentration of Chl-a (R2=0.75), but the linear correlation with TN and TP correlation is lower. THMs is correlated with the highest concentration of DOC (R2=0.87), and the correlation with N/P is the worst (R2=0.27).The average daily exposure dosage of different chemical was calculated. As the Chl-a concentration in the range of21.4～195.6μg/L, the average daily dosage of adult to MC-LR, THMs, HAAs were3.14×10-6～1.11×10-4,2.04×10～4-1.17×10-2,7.94×10-5-3.81×10-3μg/kg·day, respectively. The average daily dosage of children to MC-LR, THMs, HAAs were:1.10×10-5-3.89×104,7.15×10-4～4.44×10-22.78×10-4-1.33×10-2μg/kg·day. The health risk of algae bloom was characterized. As the Chl-a concentration is during21.4～195.6μg/L, with the increased of Chl-a concentration, the non-cancer risk is increased frequently, the health risk value is during0.17-4.39. The cancer risk of different algae polluted water is between1.26×10-5～9.25×10-4/a. The human health risk covers three different risk levels:no risk level, low risk level and high risk level. When Chl-a concentration is below80μg/L, the water belongs to no risk level. When it is between80～120μg/L, the water belongs to low risk level. When it is beyond120μg/L, the water belongs to high risk level.Algae bloom health risk assessment is only a new attempt by using health risk assessment method to guide drinking water source management but also a preliminary research in acute human risk assessment of chemical. This research has certain theoretical innovation and application value.