Objectives To investigate the environmental pollution of heavy metals, such as lead (Pb), cadmium (Cd) and chromium (Cr), in farmland in Guangdong Province and carry out a risk assessment to provide scientific basis for formulating relevant policies and prevention measures.

Methods From August to October of 2016, a total of 480 administrative villages in the eastern, western, northern and the Pearl River Delta Region of the province were selected as monitoring points. One soil sample was collected from each monitoring point and the content of heavy metals, such as Pb, Cd and Cr, were detected. Based on the Hakanson potential ecological risk index (RI) and the classical "four-step". Methods ecological risk and health risk assessment were carried out.

Results The average concentration of Pb, Cd and Cr in 480 farmland soil samples was (47.27±46.30), (0.27±0.74), (49.30±46.12) mg/kg respectively. The rate of exceeding the limits for Pb, Cd and Cr were 0.42% (2/480), 18.13% (87/480) and 3.75% (18/480) respectively, and the rate for higher than the background value were 58.33% (280/480), 86.88% (417/480) and 35.42% (170/480), respectively. Most of heavy metal comprehensive potential ecological risk indexes were moderate or higher risk, and the single potential ecological risk index was Cd > Pb > Cr. The chronic non-carcinogenic risk caused by these three heavy metals in different ways was greater in children than that in adults, but there were no significant non-carcinogenic health effects and non-carcinogenic total health risk on children and adults. The carcinogenic risk of heavy metal Cd was not more than 10^-6~10^-4, thus it was non-carcinogenic.

Conclusions The potential ecological risk index of heavy metals Pb, Cd and Cr in farmland in different areas of Guangdong Province was mostly at a moderate or higher risk level, but these heavy metals had no non-carcinogenic health risk and carcinogenic risk.