Phosphate deposits in Khouribga, Morocco, are high in cadmium; sales from the site would suffer if the European Union introduces new cadmium limits.
francesco zizola/NOOR/Redux
By Natasha Gilbert
High-stakes talks on European plans to cut levels of cadmium, a toxic heavy metal, in phosphate fertilizer are on the agenda in Brussels tomorrow. The European Commission is seeking to curtail citizens’ exposure to the compound, which has been linked to kidney and bone disease. Companies and countries that produce low-cadmium fertilizer applaud the new limits, which threaten to upend a €25 billion industry—but others are fiercely opposed. And science has been lost in the fray: Each side claims research that supports their arguments, but the studies reach similar conclusions.
“Industry is cherry-picking the science to make their case,” says Erik Smolders, a soil scientist the Catholic University of Leuven in Belgium who wrote a white paper that examined the science underpinning the proposed limits.
Fertilizers made from phosphate rock naturally contain cadmium that can accumulate in the soil; they are to blame for more than half of the heavy metal present in some agricultural soils. On average across Europe today, fertilizer contains about 32 milligrams of cadmium per kilogram (mg Cd/kg) of phosphorus, but the level can be as high as 200 mg Cd/kg, depending on where the phosphate rock is mined. Sedimentary phosphate rock found in northern Africa has naturally high cadmium levels, whereas so-called igneous rock found in Russian phosphate mines has much lower levels.
Humans can get exposed to cadmium by ingesting crops that have taken up the metal from the soil. That doesn’t appear to be a major problem in Europe; an EU-wide study published in 2015, for instance, showed that only 0.6% of 1271 nonsmoking women had an exposure higher than the “no-effect threshold.” (Smokers have higher exposures because cigarette smoke contains cadmium.) Even when smokers were included, none of the 1632 women in the study exceeded the threshold above which there is an increased risk of kidney damage; neither did 1689 children.
Still, the commission wants to reduce the risk further. In 2016, the commission proposed limiting the concentration initially to 60 mg Cd/kg, to be tightened to 40 mg Cd/kg after 3 years and to 20 mg Cd/kg after 12 years. The plan sparked a tumultuous debate and intense industry lobbying. Morocco, whose state-owned company OCP is Europe’s biggest supplier of fertilizer, stands to lose under strict controls, whereas Russia would benefit.
Two seemingly contrasting studies are at the heart of the controversy. A 2016 study led by Smolders predicts that cadmium levels in European soils will fall by 5% over the next 100 years if the limit of 60 mg Cd/kg is adopted, and by 21% at the most strict limit of 20 mg Cd/kg. In contrast, a 2017 study led by Paul Römkens, a soil and food safety scientist at Wageningen University in the Netherlands, predicts that even under the tightest limit, cadmium levels will increase by about 1% over the next century; under the looser 60 mg Cd/kg limit it would grow by nearly 10%. Smolders’s study has caught the eye of OCP and of countries like Spain and Poland, which also produce cadmium-rich fertilizer; Russian fertilizer producer PhosAgro is lobbying hard to promote Romkens’s study, which it partially funded.
Cadmium exposure is already declining. It seems there is not much evidence we are facing a problem.
But the researchers say their predictions are not so different. The main disparity is that the studies use different assumptions about the rate at which cadmium leaches down into deep soil and out of the reach of crops. Both studies acknowledge that the leaching rate is highly variable in soils across Europe—so much so that the projected cadmium levels under a 60 mg Cd/kg scenario could drop by about 60% or rise by about 50% in Smolders’s study, depending on the assumptions; the 5% drop touted by OCP is just the average scenario. In the Romkens study, the projected result after a century is somewhere between an 11% drop and a 25% rise. Both research groups say the proposed limits will at best achieve minor reductions in soil cadmium levels over very long time scales.
And with fertilizer use decreasing, some researchers question whether the new regulations are even necessary. “Cadmium exposure is already declining,” says Justus Wesseler, an agricultural economist also at Wageningen University who wrote a white paper for the European Parliament about the economic impact of the regulation. “It seems there is not much evidence we are facing a problem.”
In October last year, the European Parliament voted in favor of the commission’s limits but suggested they be implemented over a longer time frame: The 40 mg Cd/kg cap would take effect 6 years after adoption of the legislation and the 20 mg Cd/kg cap after 10 years, with the option of further delays if fertilizer supplies are endangered. Member states are split, with some nations aligning their positions with the interests of national industry.
The commission, member states, and the European Parliament will sit down this week to talk through their stark differences; they are aiming to reach an agreement in time to pass legislation by the end of June.
Source: Science Mag