Cadmium Distribution, Availability, and Translocation in Soil-Oilseed Rape (Brassica napus L.) System and Its Risk Assessment

Proper utilization of lightly contaminated farmlands is popular for developing countries such as China where there are high demands for food production to meet the needs of high population in the limited available arable lands. Oilseed rape (Brassica napus L.) is an important oil crop as well as a potential candidate for soil Cd remediation. Dietary oil ingestion is the main route of human exposure to cadmium (Cd). Therefore, understanding the characteristics of Cd transfer in the soil-oilseed rape system and its human health risk assessment are crucial for health risk alleviation and pollution control. A field experiment was conducted with 25 oilseed rape cultivars grown in a Cd (1.59 mg kg–1)-contaminated farmland where Cd was mainly from former mining activities in nearby mountains. Results showed that Cd concentrations in oilseed rape were in the order of shoots > roots > pods > seeds. The mean values of both transfer factors and bioaccumulation factors were higher than 1. Residual Cd fraction accounted for the largest proportion of the four solid components (fractions) of Cd. Cd concentration in oil ranged from 0.004 to 0.06 mg kg–1. In vitro digestion study showed that the bioaccessibility of Cd in rapeseed oil ranged from 2.48 to 30.6%. The target hazard quotients of Cd and hazard index via oil intake were below 1, and the incremental lifetime cancer risks of Cd were within the required values of 1 × 10–6–1 × 10–4. This study suggests the safety limit of Cd in rapeseed oil as 0.18 mg kg–1 based on the comparison of the carcinogenic and noncarcinogenic risks. Conclusively, oilseed rape has a good Cd accumulation capability, but the most grain Cd in plants grown in the lightly Cd-polluted soil remained non-bioaccessible with a negligible noncarcinogenic risk and an acceptable level of carcinogenic risk to human health.