New research from a joint team from Greece and Romania shows that chemicals at low levels deemed safe by regulators for each individual substance are toxic when present in mixtures.
The experiment was designed to reflect real-life scenarios, in which the general population is exposed to combinations of chemicals at low doses from dietary and environmental sources.
In an experiment on the combined toxicological effects of chemical mixtures, four groups of Sprague-Dawley rats were administered mixtures containing carbaryl, dimethoate, glyphosate (used on the majority of GM crops), methomyl, methyl parathion, triadimefon, aspartame, sodium benzoate, calcium disodium ethylene diamine tetra-acetate, ethylparaben, butylparaben, bisphenol A, and acacia gum in their drinking water for a period of 6 months.
The control group received water free from the chemical mixture.
Mixtures were administered containing each chemical in the following doses to each treatment group:
* Low dose: a quarter of the EU acceptable daily intake (ADI, the level that is supposedly safe to ingest over a long-term period)
* Medium dose: the same level as the ADI
* High dose: five times the ADI.
In relation to the animals’ body weight gain, major increases (above 10%) were observed in all male groups relative to controls throughout the 6 months follow-up period. Modest increases were observed also for the females of the medium and high dose groups, although an increase above 10% was observed only in the high dose group at 6 months.
Adverse effects were observed in liver parameters, especially at the low dose and affecting mainly male rats.
Non-linear dose responses were observed for most of the endpoints studied, meaning that the toxic effect did not increase in line with the dose, but lower doses had a more toxic effect.
Overall, the results suggest that exposure to low doses of the chemical mixture might induce liver damage as a result of the combination of different toxic mechanisms.