Fertilizers-phosphates-cadmium-cancer

Cadmium is considered carcinogenic and genotoxic by the IARC, and highly toxic to aquatic organisms. (See the IRNS toxicological data sheet here ♦). According to ANSES, nearly half of the adult population (47.6%) exceeds the toxicological reference values ​​established by the agency, and this overexposure through food is constantly increasing (1).

Due to cadmium’s toxicity, environmental groups are calling for a ban on industrial phosphate fertilizers containing this undesirable element. However, cadmium also originates from the ongoing decomposition of bedrock and is present in composts used in organic farming. Banning phosphate fertilizers would be an unnecessary constraint that responds more to misguided ideological demands than to a scientific approach. While plants tend to absorb cadmium regardless of its origin, the concentration of this heavy metal can be reduced by varietal selection, practices for conserving humus in cultivated soils, raising the pH of acidic soils, and limiting the use of certain industrial phosphate fertilizers within the limits of European regulations, which are largely sufficient..

Cadmium is readily absorbed by plants through their roots, thus contaminating the food chain. However, the bioavailability of cadmium depends on the soil pH. Cadmium is more easily absorbed in acidic soils. Cadmium mobility increases by a factor of 100 for every one pH point decrease from 6.5 to 5.5. Therefore, it is preferable for cultivated soil to have a neutral or alkaline pH.

IIt is now well established that the natural supply of cadmium from the parent rock for a very long time is the essential source of plant contamination (2) for the following reasons :

• Cadmium is an element and it does not degrade.
• It accumulates year after year in the topsoil
• Cadmium disappears from the soil very slowly, mainly carried by water from the soil to the water table, then to estuaries.

A non-existent health hazard

Nowadays, approximately 50 to 70% of the cadmium that enters the topsoil each year comes from phosphate fertilizers, “but this represents less than 0.1% of the current total cadmium stock present in the top 30 centimeters of soil” (in bold in the ANSES text (2)). In 100 years, the cadmium stock from agricultural activities is expected to increase by a maximum of 10% in cultivated soils. This is unlikely due to changes in agricultural practices in France which have led to a significant reduction in cadmium concentration in cultivated plants.

The reality of laboratory analyses is far removed from the alarmist rhetoric:

For over 15 years, the presence of cadmium has been monitored annually in common wheat, durum wheat, and potatoes harvested in France, under the auspices of industry associations (Intercéréales and CNIPT), public authorities (FranceAgriMer), and Arvalis (3).

• In potato crops, the average annual levels measured in France have remained stable for over 15 years at around 0.026 mg/kg, while the European regulatory limit is set at 0.10 mg/kg. The levels observed are therefore nearly four times lower than the regulatory threshold.
• The curve published by Arvalis shows values ​​remaining generally between 0.02 and 0.04 mg/kg since 2009, far from the red line corresponding to the European standard.
• For soft wheat, the average multi-year content is approximately 0.033 mg/kg, which is about 3 times below the European regulatory limit.
• In durum wheat, levels have decreased by about 50% since 2010, thanks in particular to varietal selection work and the improvement of agronomic practices.

Therefore, there is no need to panic and demand an immediate ban on phosphate mineral fertilizers.

To reduce the risks of cadmium concentration in food from agriculture, constraints have already been adopted on synthetic phosphate fertilizers, leading to a 70% reduction in the use of mineral phosphates in France since the 1980s. Soft wheat crops, 62% of the area no longer receive annual phosphate input.

In 2026, the maximum standards for cadmium in phosphate fertilizers are as follows:

• U.E. : 60 mg of cadmium/kg of P₂O₅.
• France : 90 mg of cadmium/kg of P₂O₅.
• ANSES recommended standard: 20 mg of cadmium per kilogram of P₂O₅ (4).

Cadmium concentration in soils and cancer risks

In France, the highly variable concentration of cadmium in the soil should lead to an increase in excess cancer mortality in certain regions. This is not the case. And sometimes the opposite is true, as shown by the maps from Santé Publique France and Gis Sol.

Some regions with low cadmium levels, such as Brittany, have very high rates of excess cancer mortality. Conversely, excess cancer mortality in Champagne is fairly average, despite having one of the highest levels of cadmium in the soil. This is also the case in the Jura, the Charente and the Alpine departments whose soils are particularly rich in cadmium, while the excess mortality rate from cancer is one of the lowest in France.

These maps clearly show that cadmium is not involved in an explosion of cancers in most regions of France when cadmium is very high in the soils (with the exception of Hauts de France, but alcohol consumption is thought to be the cause of the high cancer rate).

Predicted extractable cadmium levels in surface horizons (0-30 cm) of soils in France (source Gis Sol, 2019).

Map of excess cancer mortality in France between 2007 and 2016 (Standardized report 24-1-2019), source : Santé Publique France) ♦

Why is there no correlation between cancer and cadmium? Simply because a danger identified by laboratory tests should not be confused with the risk of exposure to that danger, which depends on the absorbed dose. The lower the absorbed dose of cadmium, the lower the risk of poisoning. Nowadays the dose absorbed by humans, which is actually tiny, does not result in a health catastrophe.

To date, only the link between cadmium and lung cancer has been established, and that is for occupational exposures in humans. For other cancers, nothing has yet been formally established. ANSES cautiously states: “It is suspected of playing a role in the incidence of certain cancers (hormone-dependent, testicular, prostate, kidney, pancreatic, etc.)” (5).

To give an example, cadmium is suspected of promoting pancreatic cancer, but the relationship between cadmium levels in the soil and pancreatic cancer does not definitively validate this hypothesis, as shown by the mapping of incidence and mortality of 24 cancers established by the French Public Health Agency. Some regions known for their cadmium-rich soils have a higher rate of pancreatic cancer (Provence-Alpes-Côte d’Azur, Nord, Picardy, etc.), but this is not the case for the Charentes or Champagne regions, where the incidence of pancreatic cancer is lower despite their very high cadmium content in soil. (6).

This frequent confusion between hazard and exposure risks is also found in the literature of environmental activists concerning pesticides, such as glyphosate (more information on the difference between hazard and exposure risks can be found here ♦). Cadmium present in the topsoil is still to this day a “trace element” largely outclassed by other well-known and documented factors on the origin of cancers (alcohol, smoking, sedentary lifestyle, obesity, unbalanced diet…).

Why is cadmium also present in the soil in organic farming?

In organic farming, synthetic fertilizers are prohibited, but not natural fertilizers. Crushed phosphate rock is considered natural and is permitted in organic agriculture. This crushed rock is sometimes found in bags of organic fertilizer sold in some garden centers or on websites. It is easy to understand that this phosphate rock adds cadmium to the soil just like conventional synthetic fertilizers, even though phosphate rock with a lower cadmium content is preferred in organic farming. It should be noted that, in the organic sector, the use of organic fertilizers containing crushed phosphate rock is reportedly limited in France. The presence of cadmium in organic food therefore likely has another origin: in addition to the decomposition of the parent rock already mentioned above, the choice of cultivated plants and the manufacturing processes of the organic fertilizers are also considered factors.

In organic farming, organic fertilizers are used instead of synthetic fertilizers. Organic fertilizers naturally contain phosphorus bound to organic molecules. For this reason, organic fertilizers should contain less cadmium.

However, plants tend to filter and concentrate heavy metals. Certain cultivated and wild plants are known to concentrate cadmium abundantly (such as corn, calamine fibrous pennywort, durum wheat, brown mustard, sunflower, cacao, and red and brown algae).

Composting organic matter does not eliminate naturally occurring cadmium; in fact, it tends to increase it through accumulation. Therefore, cadmium will be concentrated after the recycling of crop residues during composting.

It is therefore illusory to claim that organic farming makes it possible to significantly reduce plant contamination by cadmium, especially when the soils have received phosphate mineral fertilizers for decades before their conversion to organic farming, or when the soils are naturally rich in cadmium.

As for the organic fertilizers sold in some garden centers and on websites, it is regrettable that they often come from residues and manure from conventional agriculture.

Organic food and cadmium; a look back at a controversial study

Organic food and cadmium; a look back at a controversial study.

The difficulty of reducing cadmium accumulation in organic farming is confirmed by two recent studies by ANSES (French Agency for Food, Environmental and Occupational Health & Safety). The first shows that there is no difference in the levels of this undesirable element between organic and non-organic foods in France (7). The second study specifies, “In EAT3 (ANSES, 2026), it is also noted that, since the results of the statistical tests are not convergent, it is not possible to conclude regarding a difference in cadmium concentrations between organic and conventional foods. In addition to agricultural practices, it should be noted that cadmium is naturally present in agricultural soils, depending on the type of rock, whether cultivated using conventional or organic farming methods” (8).

This is sure to ruffle feathers among organic food businesses and purists, whose reaction was swift, referencing a 2014 study by Marcin Barański et al., published in the British Journal of Nutrition, which the agency claims was not mentioned in its work. The study, “Higher concentrations of antioxidants and lower concentrations of cadmium and lower incidence of pesticide residues in organic crops: a systematic review of the literature and meta-analyses,” reveals the ambition of its authors, some of whom are known for their ideological commitments and blatant conflicts of interest (for example, Charilaos Giotis was affiliated with a department of organic agriculture and food technology in Argostoli, Greece; Charles (Chuck) Benbrook, both directly and as a university researcher, served the organic food industry and anti-pesticide and anti-GMO lobbies).

The study by Marcin Barański et al. reported a 48% reduction in cadmium in organic products. This is a biased study with numerous shortcomings. For example, the authors did not address the negative aspects of organic farming, such as the generally lower protein content of grains.

The interpretation of the referenced texts in this meta-analysis is questionable. For instance, it cites a study by Crystal Smith-Spangler (9) published in the “Annals of Internal Medicine” on November 6, 2012, whereas in this study, the vast majority of data sets show no significant difference between organic and conventional products.

The interpretation of the tables used to establish the magic figure of – 48% contains inconsistencies (e.g., the sums of the data points in Table 9 do not correspond to those in Table 10).

Finally, regarding cadmium pollution, it is worth recalling that the magazine “Que Choisir” singled out organic dark chocolate from Latin America in June 2025, noting that it “showed the worst results—while still complying with standards” (10).

How to reduce cadmium contamination in agriculture using integrated methods.

First, it is essential to determine the cadmium level in cultivated soil through laboratory analysis. The cultivation method must be modified if analyses carried out every 3 or 5 years show a worrying increase in the cadmium level..

This is also an opportunity to search for other heavy metals (lead, arsenic, copper, zinc, etc.). Some COFRAC-accredited laboratories specialize in detecting pollutants in cultivated soil, which is all the more necessary when land is located near former mines and industrial areas.

The miracle solution proposed by some proponents of natural farming, advocating a ban on synthetic or organic phosphate fertilizers, is unrealistic. Phosphorus is an essential element for plant survival. Any phosphorus removed following crop exports must be replaced. Otherwise, we would witness a collapse in production and a weakening of plants, rendering them unable to resist disease.

Another solution, proposed notably by a France 2 journalist on June 4, 2026, during the 1 p.m. news broadcast, is hardly more intelligent. It suggests prioritizing foods naturally low in cadmium: tomatoes, cucumbers, eggplants, zucchini, peppers… Potatoes and all wheat and corn-based products—bread, pasta, pizza, cookies—are out. Ultimately, this would substantially reduce, everything that constitutes a staple food for the French. Let’s return to more realistic solutions, starting with reducing fertilizers containing cadmium-rich mineral phosphates. This reduction is possible, as the phosphorus reserves in French soils are now more than sufficient for decades (constituted by previous applications not used by plants). And hello to the damage to the already precarious nutritional balance of the French. It is obvious that this advice given on a public oak tree does not take into account recent progress which has led to a significant reduction in the concentration of cadmium on potatoes and soft and durum wheat.

Recent studies conducted in 205 countries have shown that the phosphorus nutrition of crops remains largely dependent on the phosphorus reserves present in the soil rather than on fertilizers applied during the growing season. Researchers have noted significant disparities in effectiveness between crops and regions. Thus, food crops are more sensitive to phosphate inputs; e.g. rice in tropical areas and wheat in temperate areas. In contrast, maize production in major growth regions such as China and the United States follows a distinct pattern of “high input for low use” (11).

Some cover crops, such as white lupin and buckwheat, can mobilize available phosphorus accumulated in the soil for other crops, thus reducing the need for phosphate fertilizers.

Other recent research has also shown that it is possible to reduce cadmium concentration in the soil by cultivating specific plants that have the advantage of fixing pollutants. A wild cruciferous plant (Noccaea caerulescens) has a high capacity for cadmium accumulation, but the technical means available for this type of treatment are still problematic, as the natural release of cadmium from the bedrock cannot be prevented, partially negating the remediation treatment. The economic impact of these remediation treatments is considerable, as the treated plots are no longer used for profitable crops for several years. What should be done with the large quantities of dry matter containing the cadmium concentrations? (Calcination would produce air pollution).

Another solution would be to cultivate profitable plant varieties that accumulate less cadmium. Research has been conducted in Canada on certain wheat varieties that have this advantage. (12). In France, the majority of the French durum wheat acreage is now cultivated with varieties carrying the cdu-1 allele, conferring the characteristic of low cadmium accumulation.

For crops requiring a significant phosphorus input, industrial phosphate fertilizers derived from volcanic rock are lower in cadmium and should be used as a priority when possible (they are not always available on the market, and reserves are not inexhaustible).

Ultimately, varietal choice, compost production from reliable sources and the reduction of cadmium-rich mineral fertilizers currently appear to be the most effective solution for reducing the concentration of this heavy metal in arable land within a reasonable timeframe. It is important to note that humus-rich soil harbors microorganisms that help release phosphorus from the soil, thus reducing the need for mineral phosphate fertilizers. The use of organic matter remains beneficial, even though there is a risk of concentration in compost, provided it is rich in balanced trace elements, particularly zinc, to benefit from its antagonistic effects against cadmium absorption. Increasing the pH of acidic soils is also essential (especially through the use of limestone inputs low in cadmium).

All the measures detailed above have a negligible impact on the cadmium levels in cultivated soils because they only affect the 0.01% introduced annually by agricultural activities. Only changes in agricultural practices have made it possible to reduce cadmium concentration in cultivated plants. It is not out of the question that further progress is possible in this direction without falling into the trap of agricultural degrowth fanatics who want to return to medieval practices.