Cadmium: a substance to be monitored
Cadmium is a trace metal element that is widespread in the environment in its natural state and as a result of human activity, particularly agriculture and industry. It is readily available for uptake by plants through their roots, by which it enters the food chain.
Cadmium is known to be carcinogenic, mutagenic and toxic to reproduction, and prolonged exposure causes kidney damage and bone fragility in humans, particularly from oral exposure via food and drinking water.
The main sources of exposure to cadmium in the general population are food, as well as tobacco for smokers. In 2011, following the second French Total Diet Study (TDS2), ANSES highlighted cases of the HBGV for cadmium being exceeded for some population groups; since this was likely to pose a health risk, it recommended reducing dietary exposure. To that end, the Agency advised acting at the source, in particular by targeting fertilisers, which were partly responsible for the increase in cadmium concentration in soils and ultimately the rise in levels of cadmium in food.
Three expert appraisal reports to better understand the exposure of the population
In its expert appraisal work, ANSES assessed the cadmium contamination cycle in relation to fertilisers and proposed new threshold values in order to prevent the occurrence of health effects and better protect consumers and workers:
- established a new HBGV by ingestion for the general population based on recent scientific studies;
- recommended lowering cadmium contamination levels as much as possible, from the application of fertilisers to the soil through to the food consumed: it proposed a maximum concentration of cadmium in mineral phosphate fertilisers and, above all, an annual cadmium inflow for all fertilisers;
- assessed the occupational exposure to cadmium of workers in the fertiliser sector.
ANSES's recommendations are part of efforts to harmonise the placing on the market of all fertilisers at both national and European levels.
Controlling the population's dietary exposure to cadmium
Following its expert appraisals, ANSES has selected the risk of osteoporosis and bone fractures as the critical effect of cadmium on human health. The proposed health-based guidance value is an oral tolerable daily intake set at 0.35 micrograms of cadmium per kilogram of body weight per day. In addition, 0.5 micrograms of cadmium per gram of creatinine in urine is proposed as the critical concentration for a 60-year-old adult, assuming that ingestion is the only source of cadmium exposure.
ANSES also recommends that cadmium inflows from fertilisers, whether industrial fertilisers or waste such as manure used to fertilise crops, should not exceed 2 grams of cadmium per hectare per year. Moreover, when mineral phosphate fertilisers are used, the Agency recommends that the cadmium concentration in the product should be less than 20 milligrams of cadmium per kilogram of phosphoric anhydride (P2O5, the main component of mineral phosphate fertilisers containing cadmium).
These thresholds appear essential to reduce the accumulation of cadmium in soils and its transfer to crops, surface water and groundwater. Applying these thresholds would strengthen the protection of population groups exposed to cadmium through food. ANSES therefore encourages further efforts at national and European levels to reduce the population's exposure to cadmium.
Insufficient data to assess occupational exposure in the fertiliser sector
Few data are available concerning biological monitoring or cadmium exposure by inhalation for workers in the fertiliser sector, from production through to use.
The sector study highlighted, on the basis of very incomplete data, cases of the occupational exposure limits (OELs) recommended by ANSES (3 micrograms per cubic metre of air) being exceeded, especially for workers in the phosphate fertiliser production sector.
Aside from in two targeted sectors for which very few data are available, no biological measurements have been taken for workers, which means that occupational exposure to cadmium cannot be rigorously assessed.
Lastly, the recommendations to lower cadmium levels in all fertilisers applied to French agricultural soils would also indirectly reduce the cadmium exposure of workers in the sector.