Arsenic is one of the most relevant global environmental toxicants. It can be accumulated in plants and animals, and can eventually be transferred to human beings. Chronic arsenic poisoning can cause serious health problems including cancers, hyperkeratosis, restrictive lung disease, and ischaemic heart disease. Research on environmental fate of arsenic has thus received increasing attention in recent years. Organic arsenic compounds (e.g., roxarsone and arsanilic acid) are widely added to animal feed to promote growth rates by controlling parasitic diseases. The resulting arsenic-bearing wastes are currently introduced to the environment (soil, pond, and river) or used to fertilize croplands. However, little is known about the environmental fate of these compounds and their environmental and health impacts.
The pollution of surroundings and farmlands around 15 hog farms used arsanilic acid as pig feed additives were investigated in Guangdong province, China. Study results showed that concentrations of arsenic in sweet potato harvested from contaminated field had reached a level of 3～6 times higher than the maximal residue limit (MRL) of 0.5 mg/kg based on the current national standard. Arsenic concentrations in soil for growing sweet potato were 25.83～55.54 mg/kg, which highly exceeded the maximal background level of 15mg/kg in soil as defined in the national standard. Moreover, arsenic concentrations in different tissues of the sweet potato directly related to arsenic concentrations in the soil. The arsenic concentrations in fish pond water exceeded the standard of fishery water quality of 0.05 mg/kg. Although arsenic concentrations in fish muscle samples did not reach the maximal residue limit(0.5 mg/kg), other edible fish tissues such as brain and fat reached a residual level of 3～4 times higher than those in the muscle. The results also showed that the range of arsenic pollution was within 200～500 meters from the pig farms, and pollutant concentrations in soil samples collected about 5m and 50m away from drainage holes had exceeded the 15 mg/kg maximal background limit. Most of rice fields with long history of recieving swine feces as fertilizer had exceeded the established maximal limit (15 mg/kg). In addition, study results suggested that rice had the ability of concentrating the arsenic. Furthermore, the arsenic concentrations in different tissues of rice presented significantly positive correlation to the concentrations in the soil.