Emerging Contaminants in Food
Improvements in the testing, identification and understanding of substances means the food industry’s understanding of contaminants, their safe levels and potential for harm is growing all the time. Hot Source explores some of the current crop of emerging contaminants.
Emerging contaminants are not necessarily new substances. They can be substances that have been around for a long time for which:
- New information has been obtained
- Test methodology has improved so a known contaminant can be tested for
- Environmental contamination is now being found in the food or water supply
- Changes in consumption of a substance result in recognition of an issue
What do these contaminants have in common? At some level they all pose a risk to people or animals.
Amygdalin is the major cyanogenic glycoside present in raw apricot kernels and products derived thereof. Raw apricot kernels have been marketed as an alternative cancer treatment. When the apricot kernel is chewed or ground it degrades into cyanide. “The lethal dose is reported to be 0.5-3.5 mg/kg body weight.”1 The acute reference dose, the point in daily exposure likely to be without risk of deleterious effects over a lifetime, as per the European Food Safety Authority (EFSA) is 20 ug/kg body weight. This level would be exceeded if a toddler consumed one small kernel or an adult consumed either three small kernels or half a large kernel.
Nickel and Other Heavy Metals
While some heavy metals are checked for and regulated, such as lead, mercury, arsenic, cadmium and chromium, others are not as clearly recognised as contaminants. However, there are issues with them too. For example, nickel is a naturally occurring metal that is sometimes found in food and water through environmental contamination. Animal studies indicate that long-term exposure can have possible reproductive and development effects.2 The International Agency for Research on Cancer (IARC) classifies metallic nickel and nickel compounds as possibly carcinogenic to humans.3 The US Environmental Protection Agency (US EPA) classifies nickel refinery dust and nickel subsulfide as a human carcinogen.
At this time, in the United States and the European Union there is no standard for nickel in food. The EFSA has set a tolerable daily intake of 2.8 mcg/kg of body weight for nickel, and the US EPA has established an oral reference dose of 0.02 mg/kg/day for nickel soluble salts. The US Food and Drug Administration (US FDA) lists elemental nickel as Generally Recognised as Safe 21 Code of Federal Regulations (CFR) 184.1537 as a direct food additive. The European Union has a drinking water and natural mineral water standard of 20 mcg/L for nickel, while in the US the drinking water and bottle water standard is 0.1 mg/L, except in some states that have drinking water standards ranging from 100 ug/L to 150 ug/L. After the EFSA performed a study in 2015 concerning nickel in food (primarily vegetables) and drinking water, experts concluded that chronic dietary exposure to nickel is of concern to the general population.
Pyrrolizidine and tropane alkaloids are natural toxins. Alkaloids are back in the news as on 19 February, 2016 European Commission Regulation EU 2016/2394 amended EU 1881/2006 establishing a limit for atropine and scopolamine, two tropane alkaloids, at 1.0 ug/kg in processed cereal-based foods and baby foods for infants and young children, containing millet, sorghum, buckwheat or their derived products.
Some pyrrolizidine alkaloids (PAs), of which there are over 600 known, are genotoxic and carcinogenic. For 1,2-unsaturated PAs the EFSA Panel on Contaminants in the Food Chain (CONTAM Panel) decided it was not appropriate to establish a tolerable daily intake. PAs are known to cause liver damage and possibly death, based on the amount and period of time during which they are consumed. In the US, outbreaks of PA intoxication are rare, but have been caused by the consumption of herbal teas and dietary supplements that contain these alkaloids. The herb comfrey (Symphytum spp.) was the main issue.5 In 2001, the US Food and Drug Administration (FDA) advised the dietary supplement industry to remove comfrey from products consumed orally.6
Between January 2014 and April 2015 a study was performed in the EU testing various products for the presence of PAs. One or more PAs were detected in 91% of the herbal teas and in 60% of the food supplements sampled.7 For measuring PAs, liquid chromatography–mass spectrometry (LC-MS/MS) has become the method of choice.
Perchlorate can be found naturally in deposits of nitrate, and potash as an environmental contaminant from the use of nitrate fertilizers as well as from the disposal of ammonium perchlorate from rocket propellants, explosives, fireworks, flares and air-bag inflators.8 At high enough concentrations perchlorate can inhibit the proper function of the thyroid gland. The US dietary reference dose is 0.7 ug/kg body weight per day.9 In Europe, for intra-Union trade, parameters were established in 2013 and then changed in 2015. These parameters include 0.75 mg/kg for dried tea and 0.02 mg/kg for foods for infants and young children – ready to eat.10 Although already established and being monitored this qualifies as an emerging contaminant because on 29 April 2015 the EU adopted further monitoring of perchlorate and in 2016 will establish maximum levels in certain foods.11
Monitoring and Identification
These are just some of the emerging contaminants. Further monitoring is being performed on brominated flame retardants in food and water. Alongside these, there is also a list including pharmaceuticals, personal care products, nanomaterials, hormones and veterinary drugs that pass from the waste stream into the water stream, and are now being found in the food supply chain. Many of these compounds are known to affect animals and humans adversely at specific levels, but investigations are ongoing into how continuous exposure at low or extremely low levels affects us. This understanding, coupled with the ability of laboratories to detect these compounds at extremely low levels, allows the industry to prevent or remove contaminated food and waters from the feed stream.12
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1 Acute health risks related to the presence of cyanogenic glycosides in raw apricot kernels and products derived from raw apricot kernels
2 Metals as contaminants in food
3 Regulations and Advisories
4 Commission Regulation (EU) 2016/239 of 19 February 2016
5 Handbook of Foodborne Pathogenic Microorganisms and Natural Toxins
6 FDA Advises Dietary Supplement Manufacturers to Remove Comfrey Products From the Market
7 Occurrence of Pyrrolizidine Alkaloids in food
9 Perchlorate Questions and Answers
10 Statement as regards the presence of perchlorate in food endorsed by the Standing Committee on Plants, Animals, Food and Feed
12 New and Emerging Water Pollutants arising from Agriculture