Insight & Opinion

Heavy Metals take global centre stage

Reintroducing leading hit industrial revolution heavy metal favourites such as Arsenic, Cadmium and Lead to your breakfast table, we take a critical look at the globalization of pollutants and what it means to you.

By Dr Garth Cambray

Lovely bright fresh vegetables can be hidden toxic waste carriers. Photo G. Cambray

Heavy metal as a music form may no longer contaminate the radio waves, but far more worryingly, heavy metals are becoming increasingly common contaminants of our foods. A combination of factors have contributed to this. In this article we will look at what has caused these problems and what it means to you.

Globally, rising energy costs have increased input costs for farmers as much as 100% over two years in certain sectors. The costs of certain foodstuffs have not however increased as rapidly, meaning that the farmer has had to accept lower prices for products. The result has been that many farmers have had to cut costs by using low cost fertilizers, and herein lies the problem.

As an example, we will use the recent cadmium contaminated zinc sulphate fertilizer problem in South Africa. A multi national fertilizer distributor operating in the Eastern Cape of South Africa sourced low cost zinc sulphate from China. This zinc sulphate contained high concentrations of cadmium and lead. The resulting effect on crops dosed with these fertilizers was contaminated fruit which has damaged the perceptions of South Africa fruit globally.

To understand how these accidents happen it is important to understand how chemicals are classified. Any chemical used for production of a product receives a classification showing what it can be used for. Hence in a laboratory one would use an Analytical Grade reagent, for food production a Food Grade reagent and for a pharmaceutical product a Pharmaceutical Grade reagent. Likewise for making paint an Industrial Grade reagent may be appropriate and for farming, an Agricultural grade product. If we look at an analytical grade reagent such as Potassium sulphate from a reputable supplier it is 99.5% pure, as are the equivalent industrial, pharmaceutical, agricultural and food grade products. The difference in the grade is what makes up the 0.5%. In a food grade product this will be something that is not toxic, whereas in an industrial grade product it could quite easily be something like lead or arsenic. Hence if one is buying chemicals for use in the production of edible foods, it is very important to ensure that the product purchased has an appropriate quality control trail from the supplier all the way back to the producer. The more paranoid the quality control system the better.

In the case of the zinc sulphate that was sold to pineapple farmers in the Eastern Cape, a chemical of an inappropriate grade was used, and despite it being of 99% purity, the 1% of impurities in the fertilizer comprised a high percentage of cadmium, lead and arsenic. The result is that for the next 15 years in some cases, levels of these metals will be quite high in the soils and this is a very expensive mistake in terms of food security. If this had happened in a place such as the Free State, or Cape wheatlands, it would seriously effect national food security.

In many cases however, the source of the heavy metals getting into food crops is not added fertilizer, but in fact irrigation water. In large parts of the Ganges valley in India little sewerage treatment capacity is available. Instead, sewerage is disposed of using the age old and highly effective system of trenches carrying sewerage to canals, which in turn carry it to agricultural areas where it is diluted with water and used to irrigate the beautiful garden produce of the worlds second most populous nation. In India, rapid industrialization has increased standards of living dramatically, and cell phone penetration into the market is monstrous. 

Generally inexpensive cell phones with nickel cadmium batteries are sold, and these batteries, due to sporadic power cuts during charging cycles have a life span of under 6 months. Disposed batteries are seldom recycled and instead end up, along with most other refuse, in gutters and landfill sites which leach directly into the sewerage system taking effluent to the fields. If one works on 200 million cell phones, that translates into a million tons of old batteries every 6 months. Cadmium is toxic in parts per billion in the environment. The result is that the incidence of heavy metal contamination, and poisoning in India is reaching epidemic proportions.

Many spices of international fame are produced in India and exported globally. The active ingredients of many spices bind heavy metals, hence it is logical to conclude that soon heavy metal contamination will damage Indian spice exports or end up in your food.

How do we protect ourselves as consumers? Our first line of defence against contaminated produce is the government. Various government departments are expected to perform quality control on products imported and produced in South Africa. In the case of fertilizer, the control is exercised in accordance with the Feeds and Fertiliser Act 36 of 1947. In 1947 the methods to detect heavy metals today were in their infancy, hence this act is useless and our government does not protect us adequately here. Private regulations which certain companies comply with however protect us far more effectively, with consumers voting with good hard currency. Certain retail food companies requires suppliers to conform to the relevant ISO standards. 

The ISO systems are audited regularly by independent bodies, and hence an ISO accredited supplier would be expected to have mechanisms in place which would ensure that problems such as the Eastern Cape pineapple contamination problem would not happen. The fact that the chemical supplier that supplied the contaminated fertilizer is an ISO accredited supplier is worrying. As our government is increasingly absent from meaningful enforcement of food safety, we have to trust the private enforcers of standards, and if these fail as well, our safety as consumers is in jeopardy. It will be important that in the light of this problem, that those that have maximum power, such as retail groups ensure that our ability in South Africa to administer ISO standards is maintained.

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