Environmental and Health Risks of Heavy Metals in Farmland Soils of Drinking Water Protection Areas and a Contaminated Paddy Field in Taiwan

Abstract

This study assessed heavy metal contents and their mobility, bioaccessibility, environmental risk, and health effects in the farmland soils of Drinking Water Source Quality Protection (DWSQP) areas contaminated by livestock manure and a paddy field contaminated by co-use of irrigation and drainage canals in Taiwan. The risk assessment code (RAC) and synthesis toxicity index (STI) for the soils were obtained. The potential health effects caused from soil direct ingestion by hand-to-mouth activity and dermal contact frequently occurring to farmers were further evaluated. The Cu, Zn, and Cr levels in DWSQP areas and the Changhwa (CH) paddy field exceeded the standards promulgated by Taiwan Environmental Protection Administration (EPA). Nevertheless, RAC in DWSQP areas was in low risk levels. In contrast, RAC from Cu and Zn in CH paddy soils was in medium levels. Non-carcinogenic risks for farmers based on the total and bioaccessible metals in DWSQP areas and CH soils were all <1. However, carcinogenic risks based on bioaccessible Cr still exceeded 10−6 in several soils, indicating that the potential impacts on environmental and human health due to direct and indirect exposures to these contaminated soils should be concerned.

Transition Metals in Freshwater Crustaceans, Tilapia, and Inland Water: Hazardous to the Population of the Small Island Province

“…It showed that the average population life time cancer risk associated with crustaceans and tilapia consumption (0.007–0.012) and ingestion of SW and GW (1.423 × 10 −7 –2.607 × 10 −2 ) would result to approximately 1 case per 100,000 population. As per the U.S. Environmental Protection Agency [ 16 ], the value of 10 −5 is an acceptable lifetime carcinogenic risk. However, it should be noted that the PER of the island for metals in crustaceans and tilapia was high.…”

“…Long-term exposure to crustaceans, tilapia, and inland water in Marinduque may result to one cancer patient per 100,000 population, which according to USEPA [ 16 ] is acceptable. Crustaceans, tilapia, and inland water were only the three edible items in Marinduque considered in the calculation of cancer risk probability in this study.…”

“…There were various studies focusing on river and coastal water quality, sediments, and human health in Marinduque [ 8 , 9 , 10 , 11 , 12 ] and neighboring countries [ 13 , 14 , 15 , 16 ]. However, there was very limited study on metal detection in freshwater crustaceans and tilapia (fish) and the spatial distribution of the potential ecological risks (PER) posed by these freshwater fish together with inland water quality.…”

Farmland Trace Metal Contamination and Management Model—Model Development and a Case Study in Central Taiwan

“…The sources of TMs in canal irrigation systems include the transport of irrigation water and sediment in each square meter. The annual runoff volume, QR (m 3 /m 2 /year), can be calculated from the field water balance expressed as QR = QI + QP − ET − QL (5) where QI (m 3 /m 2 /year) is irrigation, QP (m 3 /m 2 /year) is precipitation, ET (m 3 /m 2 /year) is evapotranspiration, and QL (m 3 /m 2 /year) is percolation within each unit area per year. In addition, the different mass transportation paths can be expressed as the following equations, respectively:…”

“…Due to the low mobility of TMs in a soil environment [3], they are not easily diffused or diluted, so they easily accumulate in surface soil. Soil contaminated with TMs in agricultural areas is likely to affect people's health and safety once the TMs have translocated into the edible parts of crops [4,5]. TMs also affect the growth and quality of crops [6].…”