Watching CBS morning news on December 6, 2011, it was claimed a way to reduce heavy metal consumption (especially inorganic arsenic) was to buy organic food. the CBS website has the clip here, the claim is made at 2:30.

Is there any proof organic farming methods produce food with fewer heavy metals than conventional farming methods? Additionally, any information on the requirements for a farm to be classified as organic would be helpful. Does prior soil contamination matter?

  • The other issue answers might usefully address is whether the levels of heavy metals (or any other contaminants) is in any way significant for health. – matt_black Dec 7 '11 at 17:53
up vote 13 down vote accepted

No.

Your first question was to define what organic farming means. The definition given by the United States Environmental Protection Agency is

"Organically grown" food is food grown and processed using no synthetic fertilizers or pesticides. Pesticides derived from natural sources (such as biological pesticides) may be used in producing organically grown food.

Most places organic food is certified, the rules varying by region.

Your second question was does organic farming produce food with less heavy metals? The answer is no.

Organic Food: Buying More Safety or Just Peace of Mind? A Critical Review of the Literature
Faidon Magkos, Fotini Arvaniti, Antonis Zampelas
Critical Reviews in Food Science and Nutrition
Vol. 46, Iss. 1, 2007
[Emphasis mine]

Chemical contaminants in food that result from general environmental pollution [cadmium (Cd), mercury, copper, arsenic, zinc, lead, dioxins, polychlorinated biphenyls (PCBs), radioactive nuclides, OCPs] are also potent and may pose serious acute and/or chronic health risks

...

It is generally accepted that persistent pollutants in the soil such as chlorinated hydrocarbons and certain heavy metals cannot be avoided through organic farming practices.

...

most studies indicate similar levels of contamination by these pollutants in a variety of both organic and conventional food products; where differences have shown up, they don't consistently give the edge to either type of food (Lecerf, 1995; Woese et al., 1997; Worthington, 2001; Slanina, 1995; Kumpulainen, 2001; Jorhem and Slanina, 2000; Malmauret et al., 2002). It may be that the variability within a given crop is greater than the variability between one cultivation system and another (Jorhem and Slanina, 2000).

Contaminants in organic and conventional foodstuffs in France
L. Malmauret, D. Parent-Massin, J.-L. Hardy, P. Verger
Food Additives and Contaminants
Vol. 19, Iss. 6, 2010

The aim was to compare the levels of contamination in organic and conventional raw materials. To this end, the level of contamination by heavy metals (lead, cadmium, arsenic, mercury), nitrates and nitrites, and some mycotoxins were monitored. Fifteen products were tested in their organic and conventional forms, including meat, milk, eggs, vegetables and cereals. The median levels of contamination were calculated and compared with the recommended or regulated maximum levels. The maximum levels were exceeded for lead in organic carrots and buckwheat, and in conventional wheat; for cadmium, in both organic and conventional buckwheat; for nitrates, in organic spinach; and for patulin in organic apples. Moreover, contamination of both conventional and organic wheat by deoxynivalenol was observed with a higher level in organic products. However, the health risk for consumers might be real only for the contamination by mycotoxins as the contaminated foods (apples, wheat) are the main contributors to total exposure.

  • My understanding is that some pesticides contain heavy metals - I don't know how common or even correct that is. However, long term use of such compounds seems more likely to cause a build up in soil, which could lead to higher levels in some crops. I'm not an authority on the topic, so would very much appreciate feedback on how much of an issue it is. – Highly Irregular Jan 19 '12 at 9:51

Looking on the net i find no conclusive studies. However it is known that mineral fertiliser and sludges are one of the main contribution of soil contamination, and the main source of contamination when lands are away from industry and fioul heated area.

A recent study in Sweden made by public agency estimated that cadmium contamination via food was responsible of 10 % of the total cost of bone fracture (400 million dollars out of 3.8 billion). They have not estimated the cost of induced cancer, kidney failure and unfertility as those are more tricky. One can thus expect at a well conducted study will show some effect on the cadmium side.

The problem is that a comparison has to be done on the same type of soil, with two close by production (conventional and organic) and the organic production should have taken place for a long enough period, otherwise there cannot be any difference in the soil matter.

To my knowledge, such a study still remains to be conducted.

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

  • 1
    Welcome to Skeptics! Please provide some references to support your claims. The fact that you personally cannot find any studies isn't sufficient. In particular, note that @SamIAm's answer appears to contain one. In this situation, I try to find some peer-reviewed source (or revert to an appeal to appropriate authority) arguing there is no such research. Please give a specific reference to the Swedish study so we can see for ourselves whether it supports your argument. – Oddthinking Mar 14 '14 at 6:22

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