Chemical cocktails in foods increase cancer risk
The risk of getting cancer from carcinogens increases dramatically when the substances are mixed.
One plus one doesn't always make two when toxic chemicals are involved.
This has been demonstrated in a new study that found that the carcinogenic effect of a cocktail of substances is greater than the effect of the individual substances added together.
The study focuses on the fact that the regulations governing toxic substances in foods is probably inadequate.
"Our study shows that if we don't take the cocktail effect into account when determining the limit values for potentially carcinogenic substances we tend to set the limit values too high," says Kristian Syberg, associate professor at the Department of Environmental, Social and Spatial Change (ENSPAC) at Roskilde University.
"The cocktail effect of potentially carcinogenic substances is so great that the limit values need to be set even lower if we’re to have the desired safety margin for concentrations of the substances," he says.
The new study has been published in the Journal of Toxicology and Environmental Health.
Cocktail devastates the DNA
In the study, Syberg examined the combination effect of two pesticides and the substance acrylamide which is typically found in breads, coffee, potato chips, and other types of food.
On their own, each substance is potentially a carcinogenic, but added together the carcinogenic effect is far greater, the study shows.
In his experiments, Syberg exposed cells to a combination of the three substances and examined how the DNA inside the cells was damaged by the cocktail.
The experiments showed that the cocktail of potentially carcinogenic substances did more damage to the DNA, even in concentrations of the individual substances that were so low that they would have no effect on their own.
This means that if you don't take the cocktail effect into account, then you underestimate the toxicity of the substances in the environment, says Syberg. "That's scary."
Important to not focus on individual chemicals only
Eva Cecilie Bonefeld-Jørgensen is a professor of toxicology and the head of the Centre for Arctic Health at Aarhus University.
She has read the new study and finds it exciting that the cocktail effect not only applies to endocrine-disrupting substances but also to carcinogenic substances.
“The study is an excellent example of how we shouldn't simply believe that the overall toxic effect of a number of substances is equal to the toxic effect of the substances added together,” says Bonefeld-Jørgensen. "The individual substances actually tell us nothing, because we’re never exposed to just one of the substances at a time."
"What’s particularly interesting about the study is seeing how the cocktail effect is in particular is greater than the combined effect in small concentrations. It's important when regulating that we take the quantities of the given substances we permit into account," says Bonefeld-Jørgensen, who would’ve liked if Syberg had also examined whether the concentrations of the substances used in the study are comparable to those found in humans.
Study is ’proof of concept’
In the study, Syberg explains, they made use of high concentrations of the potentially carcinogenic substances because the exposure only lasted 48 hours.
The study is as such more 'proof of concept' than it is about the acute risk to the population, he says.
"Since this field has only been vaguely examined, we found it significant to do a study that shows how important it is to investigate the cocktail effect of potentially carcinogenic substances before the authorities attempt to calculate a risk," says Syberg.
The cocktail effect is unknown
Limit values for substances in the environment or in products are established on the basis of an examination of the substances' harmful effects.
Scientists investigate, for instance, how small a quantity of a substance it takes to have a harmful effect on cells, humans or animals, as well as whether the substances can cause cancer or disrupt the endocrines.
They then set some limit values for the discharge and use of the substances.
One cannot, however, take it for granted that cells, humans, and animals will react in the same way to the substances individually as they do when the substances are part of a cocktail.
The limit values determined may therefore be too high, even if the authorities apply precautionary principles when determining them.
"Some substances may, for instance, render the cells' cell membranes more penetrable for other substances. This means that these other substances can penetrate the cells and do much more damage than they were able to in tests where the substances were on their own. It’s this kind of effect in cocktails which the authorities don’t take into account in their risk assessment," says Syberg.
Translated by: Hugh Matthews
- Mixture Genotoxicity of 2,4-Dichlorophenoxyacetic Acid, Acrylamide, and Maleic Hydrazide on Human Caco-2 Cells Assessed with Comet Assay, Journal of Toxicology and Environmental Health, DOI:10.1080/15287394.2014.983626