Parliament Publications & Records 1990
Reports of contact dermatitis
...Previous experience at the Scottish Crop Research Institute reinforces the evidence and has revealed similar problems for staff working with Brassicas as well as other related plants. The problems range from rashes and blisters, especially on the face and hands, but occasionally more widespread - for example, for staff wearing shorts or short-sleeved shirts - all the way to asthma and hayfever. For some staff the problems have become so severe that they have had to discontinue work with Brassica crops. For others there has been a need to avoid contact with those crops, most usually at the time of flowering, either by not entering the glasshouses or seed production tunnels where the plants are in flower, or by wearing gloves or using barrier creams...We need to ascertain whether the problem relates purely to pollen release or involves chemicals released by the plant, some of which are mustard oils, which are known from other work to cause acute irritation to skin and mucous membranes.
Toxicity in Animals
There have been numerous anecdotal reports of domestic and wild animals, e.g. dogs, roe deer and rabbits, becoming unwell/dying after eating oilseed rape foliage and/or seeds. These anecdotal reports have been supported by a number of studies which have confirmed the oilseed rape crops are extremely toxic to animals both when grown in the field and after crushing into animal feed.
Glucosinolates in crops, such as oilseed rape (Brassica napus) and Brassica vegetables, is undesirable because of the toxicological effects of their breakdown products. – Breakdown products include nitriles, isothiocyanates, thiocyanates, epithionitriles and vinyl oxazolidinethiones (Naturally Occurring Toxicants as Etiologic Agents of Foodborne Disease).
Volatile mustard oils belong to the glucosinolates which are a class of ca. 100 secondary plant compounds (Kjaer and Skrydstrup, 1987) generally found in Brassicaceae. These compounds have a similar structure characterised by a common part containing a β-thioglucose coupled with a sulfonated oxime group and by a variable organic side chain constituted by alkyl, alcenyl, hydroxy-alcenyl, aryl, indolyl, sulfinyl, sulfonyl or thio residues. They are present in glycosides and released after hydrolysis (by enzymes in the presence of moisture). Present in high or low level (00 varieties) in rapeseed and in rapeseed meals, these molecules are easily broken down during animal digestion, leading to compounds with detrimental and antinutritional characteristics. - Opinion of the Scientific Committee on Animal Nutrition on Undesirable Substances in Feed, April 2003.
Although a great deal of research and manipulation has succeeded in limiting the amount of glucosinolates in the seed (presently reduced to 18 micromoles or less) this has had little, if any, impact on the glucosinolate level in the foliage.
Paik reported that the toxic effects were thought to be due to glucosinolate hydrolysis products, such as nitriles and isothiocyanates, formed either within the meal or within the digestive tract of the animal.
Ingestion of powdered mustard seed or of volatile oil of mustard in sufficient amount results in gastroenteritis ”which may prove fatal” (Watt and Breyer-Brandwijk, 1962).
Bell reported the following effects in animals which have consumed crucifer-seed meals or diets high in crucifers; growth depression, markedly reduced feed intake; enlargement of target organs (liver, kidneys, thyroid) and depletion of plasma thyroxine.
Allyl isothiocyanate (common: volatile mustard oil) is present among others in horseradish, rapeseed and some mustard species. The volatile oil of these mustard species contains glycosides called sinigrine or sinalbine which are degraded by the enzyme myrosine to allylthiocyanate (and glucose and potassium bisulfate). The clinical symptoms are an acute gastroenteritis (colic, diarrhoea, foaming at the mouth), respiratory disturbances and probably photosensibility.
The organic compound volatile mustard oil (ally isothiocyanate) listed in annex to Directive 1999/29/EC is a natural constituent (or derived from natural constituents) of plants used for feed purposes. Above certain concentrations, it affects the health of domestic animals while they are without effects on the human consumer of products derived thereof. The toxic potential of this plant constituent is recognised by feed manufacturers who take into consideration their adverse effects when formulating a ration [this does little to allay fears about the toxic potential of this plant constituent on wild animals or domestic pets that might ingest either the oilseed pods or plant foliage in the field] - Opinion of the Scientific Committee on Animal Nutrition on Undesirable Substances in Feed, April 2003.
Because of the vast area of oilseed rape grown in the UK, some 500,000 hectares grown for human consumption and many more thousands of hectares grown for industrial processing, it would appear that oilseed rape crops may well present a toxic hazard to both wild animals and domestic pets.
Erucic acid and the rapeseed oil ban of 1954
Rapeseed oil had certain negative characteristics which led to the Canadian Department of National Health and Welfare imposing a ban on all sales of oil for edible purposes in 1956. The ban was rescinded some three months later due to the insistance of the crop breeders that there was only minimal human consumption of rapeseed at that time. Although the ban was never implemented, the perception remained that health problems could arise from rapeseed oil consumption because erucic acid was found to cause heart lesions in rats fed on a rapeseed diet. The breeders shifted their focus onto reducing the erucic acid content of the seed.
Rapeseed oil scare about its erucic acid content in 1970
By 1964, the breeders had successfully reduced the erucic acid content of the seed from 40% down to 10%. In 1970 another health scare circulated about the serious health implications of erucic acid in the diet. This was confirmed in research published by the plant breeders in 1970.
By 1974, the erucic acid content had been reduced down to 5% and the plant breeders phased-in the (healthier) lower erucic acid rapeseed as a replacement for the higher erucic rapeseed that continued to be sold to the public as an edible oilseed. The replacement rapeseed was marketed as the “healthier option”.
Toxicity of Erucic Acid in Rapeseed Oil
Erucic acid is a monosaturated 22 carbon long chain fatty acid with a single double bond (C22:1). Erucic acid is also known as cis-13-Docosenoic acid. Through extensive crop breeding/selection the plant breeder were able to substantially reduce the amount of erucic acid found in the oil to a level (below 5%) that was considered to be less harmful to human health.
Today, oilseed rape grown for edible consumption contains less than 2% erucic acid. Oilseed rape cultivated for industrial use still contains high levels of erucic acid (40-60%). Using genetic manipulation the breeders are striving to increase the level of erucic acid to 70-80% to maximise on its industrial potential.
The structural chemical formula for erucic acid is CH3(CH2)7CH=CH(CH2)11COOH, the trans isomer is known as brassidic acid. Erucic has been shown to have a variety of health impacts in previous studies.
It is concerning to note from the published literature that a specific level (percentage) of erucic in the oil does not appear to have been stated that will ensure that erucic acid is not harmful to human health. One can only speculate that the risks to human health still remains but the risks have been minimised to the lowest practicable level by the plant breeders.
Carcinogenic Rapeseed Cooking Oil
Qu et al. in 1992 reported that the condensate of volatile emissions from unrefined rapeseed cooking oil, frequently used for frying in China, was found to be mutagenic and produced chromosomal damage in the bone marrow of orally treated mice. The investigations suggested that the reported association of exposure to Chinese rapeseed cooking oil emissions and lung cancer risk may be related to the mutagenic component of these condensates.
Researchers from the Shanghai Cancer Institute and the US National Cancer Institute found that unrefined rapeseed oil produced much larger amounts of carcinogens such as bezene and formaldehyde than other cooking oils. The smoke is also much more carcinogenic than that produced by other cooking oils.
At high temperatures, refined rapeseed oil used in the West is reported to give off a similar amount of carcinogens as the unrefined Chinese oil.
From the published literature it would appear that most (if not all) cooking oils become hazardous to health when heated to temperatures in excess of 200oC. However, it is also noted from the literature that oilseed rape (including canola and rapeseed) oil appears to be more hazardous than most of the other cooking oils. From the literature, it would appear that the higher the linolenic content of the oil, the greater the risks to human health. These problems lead to the development of oilseed varieties high oleic/low linolenic .
Toxic Allergy Syndrome
Tabuenca in 1981 reported that the toxic allergy syndrome epidemic in Spain which caused more than 300 deaths and 20,000 hospital admissions was caused by ingestion of rapeseed oil denaturated with aniline.
Toxic oil syndrome resulted from the consumption of rapeseed oil that had been denatured with 2 percent aniline for industrial use, subsequently refined, and then illicitly sold as pure olive oil. To date, the causal agent remains unknown, as many substances which could potentially be the causative compound have been found in the implicated oils.
Examining the most current published literature on toxic allergy syndrome indicates that research scientists have discovered that the syndrome appears to have an immunotoxicological basis. However, as indicated above, the causal agent remains unknown, and due to the way in which the initial research was carried out, the causal agent may never be identified.
It is interesting to note from the literature that no mentions appears to have been made about the fact that the industrial rapeseed oil, deliberately denatured with aniline to prevent it entering the food chain, may have contained in excess of 40% erucic acid. Given the serious health implications stated in previous published literature regarding the consumption of erucic acid, this would appear compelling evidence of harm particlularly since the research scientists have concluded that the causal agent has an immunotoxicological basis.
Author - Armitage; copyright 2007
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