Mixture risk assessment due to ingestion of arsenic, copper, and zinc from milkfish farmed in contaminated coastal areas.

Human health risks associated with the consumption of metal-contaminated fish over extended periods have become a concern particularly in Taiwan, where fish is consumed on a large scale. This study applied the interaction-based hazard index (HI) to assess the mixture health risks for fishers and non-fishers who consume the arsenic (As), copper (Cu), and zinc (Zn) contaminated milkfish from As-contaminated coastal areas in Taiwan, taking into account joint toxic actions and potential toxic interactions. We showed that the interactions of As-Zn and Cu-Zn were antagonistic, whereas As-Cu interaction was additive. We found that HI estimates without interactions considered were 1.3-1.6 times higher than interactive HIs. Probability distributions of HI estimates for non-fishers were less than 1, whereas all 97.5%-tile HI estimates for fishers were >1. Analytical results revealed that the level of inorganic As in milkfish was the main contributor to HIs, indicating a health risk posed to consumers of fish farmed in As-contaminated areas. However, we found that Zn supplementation could significantly decrease As-induced risk of hematological effect by activating a Zn-dependent enzyme. In order to improve the accuracy of health risk due to exposure to multiple metals, further toxicological data, regular environmental monitoring, dietary survey, and refinement approaches for interactive risk assessment are warranted.

An integrated GIS-based approach in assessing carcinogenic risks via food-chain exposure in arsenic-affected groundwater areas.

This study presented an integrated GIS-based approach for assessing potential carcinogenic risks via food-chain exposure of ingesting inorganic arsenic (As) in aquacultural tilapia, milkfish, mullet, and clam in the As-affected groundwater areas. To integrate spatial information, geographic information system (GIS) was adopted to combine polygon-shaped features of aquacultural species with cell-shaped features of As contamination in groundwater. Owing to sparse measured data, Monte Carlo simulation and sequential indicator simulation were used to characterize the uncertainty of assessed parameters. Target cancer risks (TRs) of ingesting As contents at fish ponds were spatially mapped to assess potential risks to human health. The analyzed results reveal that clam farmed at the western coastal ponds and milkfish farmed at the southwestern coastal ponds have high risks to human health, whereas tilapia cultivated mainly at the inland ponds only has high risks at the 95th percentile of TR. Mullet in general has low risks to human health. Moreover, to decrease risks, this study suggests reducing the use of As-affected groundwater at clam and milkfish ponds due to high bioconcentration factor (BCF) of clam and inorganic As accumulation ratio of milkfish. The integrated GIS-based approach can provide fishery administrators with an effective management strategy at specific fish ponds with high risks to human health.

Low-cost farmed shrimp shells could remove arsenic from solutions kinetically.

The purpose of this study was to explore the ability of shrimp shell to remove arsenic (As) from aqueous solutions by experimental and modeling analyses. The shells of two species of farmed shrimp, black tiger shrimp (Penaeus monodon) and white shrimp (Litopenaeus vannamei), were chosen to be the sorbents. The results indicate that sorption capacities of black tiger shrimp and white shrimp shells were estimated to be 8.1 x 10(-3) to 5.0 x 10(-1) and 7.8 x 10(-3) to 2.4 x 10(-1)mgg(-1), respectively. Results show that the sorption capacities of the shell of black tiger shrimp did not significantly differ from those of white shrimp by through analysis of variance ANOVA (F=1.50, n=18, P>0.05). This study found that Langmuir and Fruendlich isotherm models described the adsorption processes well (r(2)>0.90). The Langmuir-based maximum adsorption capacity was estimated to be 0.125-0.126 mg g(-1), whereas the Fruendlich-based adsorption capacities ranged from 0.105 to 0.124 mg g(-1). Model analysis based on pseudo-second-order kinetics reveals that sorption capacity of shrimp shell increases with the initial As concentration and retention time in water. Based on isotherm and kinetic analyses, the sorption capacity of shell of black tiger shrimp is slight higher but insignificant than that of shell of white shrimp for As removal from solution. A combination of experiments and modeling suggests that shrimp shell, as a waste material, could be utilized potentially for the removal of As from an aqueous medium. Although the As-removal capacity of shrimp shell was lower than those of natural and chemical sorbents, using shrimp shells as sorbents is less expensive and could increase the additional benefit of shrimp products.

Risk assessment on mixture toxicity of arsenic, zinc and copper intake from consumption of milkfish, Chanos chanos (Forsskål), cultured using contaminated groundwater in Southwest Taiwan.

Studies on bioaccumulation of arsenic, zinc, and copper in freshwater-cultured milkfish were carried out to assess the risks on human health. The arsenic, zinc, and copper levels in milkfish showed significant positive correlations to the arsenic, zinc, and copper concentrations in pond water. The hazard index of arsenic, zinc, and copper mixture for intake of milkfish (1.75 +/- 0.65) demonstrated that intake of in this way contaminated milkfish will result in non-carcinogenic risk. The target cancer risk of arsenic for intake of the milkfish (2.74 x 10(-4) +/- 1.18 x 10(-4)) indicated that the inhabitants were exposed to arsenic pollution with carcinogenic risk.

Toxicokinetics/toxicodynamics of arsenic for farmed juvenile milkfish Chanos chanos and human consumption risk in BFD-endemic area of Taiwan.

This paper presents a toxicokinetic/toxicodynamic analysis to appraise arsenic (As) bioaccumulation in farmed juvenile milkfish Chanos chanos at blackfoot disease (BFD)-endemic area in Taiwan, whereas probabilistic incremental lifetime cancer risk (ILCR) and hazard quotient (HQ) models are also employed to assess the range of exposures for the fishers and non-fishers who eat the contaminated fish. We conducted a 7-day exposure experiment to obtain toxicokinetic parameters, whereas a simple critical body burden toxicity model was verified with LC50(t) data obtained from a 7-day acute toxicity bioassay. Acute toxicity bioassay indicates that 96-h LC50 for juvenile milkfish exposed to As is 7.29 (95% CI: 3.10-10.47) mg l(-1). Our risk analysis for milkfish reared in BFD-endemic area indicates a low likelihood that survival is being affected by waterborne As. Human risk analysis demonstrates that 90%-tile probability exposure ILCRs for fishers in BFD-endemic area have orders of magnitude of 10(-3), indicating a high potential carcinogenic risk, whereas there is no significant cancer risk for non-fishers (ILCRs around 10(-5)). All predicted 90%-tiles of HQ are less than 1 for non-fishers, yet larger than 10 for fishers which indicate larger contributions from farmed milkfish consumptions. Sensitivity analysis indicates that to increase the accuracy of the results, efforts should focus on a better definition of probability distributions for milkfish daily consumption rate and As level in milkfish. Here we show that theoretical human health risks for consuming As-contaminated milkfish in the BFD-endemic area are alarming under a conservative condition based on a probabilistic risk assessment model.

Shell of abalone Haliotis diversicolor supertexta can eliminate waterborne zinc biokinetically.

Dietary and nondietary accumulation of waterborne zinc (Zn) by shell of abalone Haliotis diversicolor supertexta was studied to determine if abalone shell can accumulate and eliminate Zn biokinetically. Shell of H. diversicolor supertexta rapidly accumulated Zn at microgram per gram concentrations during a 7-d uptake period for dietary and nondietary exposure to 1 microgml(-1) Zn seawater. Depuration half-lives were 7.22 and 15.40 d for dietary and nondietary exposure, respectively. The uptake rate constants were 5.12 and 4.84 ml g(-1)d(-1), respectively, for dietary and nondietary exposure. The depuration rate constants were 0.048 and 0.10 d(-1), respectively for dietary and nondietary exposure. Results from this study showed that the shell of H. diversicolor supertexta accumulated Zn and that it reflected the composition of the seawater in which the abalone lived. This suggested that the shell of H. diversicolor supertexta can be used as a bioindicator or can act as a receptor to biokinetically eliminate heavy metals from aquatic food webs.

Acute toxicity and bioaccumulation of arsenic in tilapia (Oreochromis mossambicus) from a blackfoot disease area in Taiwan.

The general objective of our work was to determine the acute toxicity and bioaccumulation of arsenic (As) in tilapia (Oreochromis mossambicus) from the blackfoot disease (BFD) area in Taiwan. The average concentration of As in pond water ranged from 17.8 to 49 microg L(-1). Acute toxicity tests showed that the As concentration that caused toxicity to tilapia ranged from 69 060 microg As L(-1), in the 24-h toxicity test, to 28 680 microg As L(-1), in the 96-h toxicity test. We measured As concentrations in various tissues of tilapia to identify the affinities of tissues for As. Significant correlations were found among the As concentrations in all tissues. The highest bioconcentration factor (BCF) was found in the intestine (maximum value: 2270). The order of BCFs was: intestine > stomach > liver approximately gill > muscle. Arsenic concentrations in all tissues were allometric, negatively correlating with fish body weight [r(2) = 0.63 +/- 0.045 (mean +/- SE), p < 0.05]. Our results also revealed that As concentrations in muscle tissue were positively correlated with As accumulation in the viscera (r(2) = 0.85, p < 0.05). Significantly higher concentrations of As were obtained in the viscera of tilapia [12.65 +/- 10.17 microg g(-1) dry wt (mean +/- SD)] than in the muscle tissue (3.55 +/- 0.42 microg g(-1) dry wt). Our results suggest that a simple way of reducing the health risk associated with consuming tilapia is to trim and cook the fish properly, that is, removing the viscera of tilapia can greatly reduce the amount of As ingested and consequently reduce the health risks.

Linking biokinetics and consumer-resource dynamics of zinc accumulation in pond abalone Haliotis diversicolor supertexta.

A dynamic model that links biokinetics and consumer-resource dynamics for describing zinc (Zn) accumulation in abalone Haliotis diversicolor supertexta has been developed and then applied to Zn data from real abalone farms. The biokinetic parameters used in this study, uptake and depuration rate constants of abalone and their food source, red alga Gracilaria tenuistipitata var. liui, were obtained from a laboratory 14-d exposure experiment. We carried out a sensitivity analysis of the model by using the fractional factorial design technique, taking into account the influence of consumer-resource-related parameters such as growth and death rates and biomass and biokinetic parameters characterized by bioconcentration factor. Results indicate that the response time of biomagnification dynamics of Zn accumulation in abalone was influenced mainly by the growth rate of algae and biomass and the death rate of abalone and by interactions algae biomass and abalone death rate and abalone and algae biomass. New algae production results in substantially higher values of biomagnification factor. The linked model was then applied to field observations from a real-life situation of variable Zn concentrations occurring in abalone farms. Simulation results show that the predicted values are within a factor of 2 of the measured values (% errors range from 5.3 +/- 4% to 44.1+/- 8%). Both model analysis and model application to the abalone farms suggest that the linking influences between biokinetics and consumer-resource dynamics support Zn accumulation in H. diversicolor supertexta and in G. tenuistipitata var. liui as functions of Zn concentration in water and abundance of food occurring in abalone farms.

Coupling toxicokinetics and pharmacodynamics for predicting survival of abalone (Haliotis diversicolor supertexta) exposed to waterborne zinc.

We developed a mortality model, by coupling an acute toxicity model and a pharmacodynamic model, to predict survival of abalone (Haliotis diversicolor supertexta) exposed to waterborne zinc (Zn). We conducted a laboratory 14-day exposure experiment to obtain biokinetic parameters of depuration rate constant (k(2)) and bioconcentration factor (BCF). A one-compartment uptake-depuration model was used to fit the exposure data to estimate BCF and k(2) values. The acute toxicity model was developed based on the receptor theory and was verified with LC(50)(t) data obtained from a 7-day acute toxicity test. A highly significant correlation (r(2) = 0.98) was found between predictions and LC(50)(t) data for the acute toxicity model, indicating a successful description of 7-day LC(50)(t) data of Zn in abalone. The predicted time course of lethal body burden of Zn in abalone was compared with measured data, showing that the average percent error was 14.04 +/- 3.02%. A refined pharmacodynamic model was expressed as the Hill equation, which in terms of waterborne Zn and LC(50)(t) data was used to fit observed mortality percentages to determine the Hill coefficient (r(2) = 0.98). The proposed mortality model in terms of whole body burden and lethal body burden at site of action was then employed to predict the time-varying mortality of abalone exposed to various Zn concentrations in pond water. Our results demonstrate that 96-h LC(50) and incipient LC(50) for H. diversicolor supertexta exposed to Zn are 1.1 and 1.05 mg L(-1), respectively. Our predictions also demonstrate that equilibrium lethal body burden at site of action is about 198 microg g(-1), whereas the mortalities never reach 50% when H. diversicolor supertexta exposed to Zn is < or = 1 mg L(-1).