Toxicokinetics

Transcription

Hello, my name is Jean-Lou. I’m a toxicologist at EFSA. My work involves developing methods for assessing the safety of chemicals in food and the environment. Today, I’m going to talk about the risk assessment of multiple chemicals in food often called chemical mixtures. First of all, what do we mean by ‘chemical mixtures’? “Chemical mixtures” refer to combined exposure to multiple chemicals. Food may contain many different chemicals naturally occurring such as nutrients and plant toxins produced by weeds, or man-made chemicals such as pesticides and environmental contaminants like dioxins. The number of combinations of chemicals is practically infinite and they can come from a variety of sources: food, medicines or consumer products such as cosmetics. These chemicals may raise health concerns depending on their toxicity and the level of exposure in food or the environment. So, how do scientists assess consumer safety for a single chemical? For a single chemical scientists review all the toxicological data to set a safe level of use and compare it with consumer exposure through food, to conclude on any potential health risk. What about multiple chemicals? For multiple chemicals, scientists have developed risk assessment methods which use the same principles as for single chemicals with some differences. First of all, the beginning of the process is the problem formulation to define whether a risk assessment for a group of chemicals is needed based on the nature of the exposure in consumers or depending on their toxicity. Who is exposed and by how much? Is the exposure a one-off or is spread over time? The next step is to assess the toxicity of the group of chemicals and identify how they act, often referred to as “mode of action”. Scientists analyse the information available on the toxicity using scientific criteria in a so-called “weight of evidence approach”. Three assumptions about the toxicity are used to then conclude on the health risks – dose addition, response addition and interaction –. Dose addition means that the chemicals have a similar toxicity/mode of action and after determining their individual potency, the doses are added for the risk assessment. Response addition means that the chemicals have independent toxic effects and the measures of toxicity are added for the risk assessment. Interactions are more complex. Chemicals can become more toxic when combined, which is called “synergism”. On the other hand, they can be less toxic when combined, which is known as “antagonism”. The mechanisms behind synergism and antagonism are complex, however, two important ones involve an increase or decrease in the body’s ability to detoxify and eliminate the compounds, which is called toxicokinetics, and an increase or decrease in toxicity, which is called toxicodynamics. If there is evidence of such interactions, scientists collect the information to take these effects into account in the risk assessment. Efsa is very active in this field and has developed methods for the risk assessment of multiple chemicals both for human health and the environment. Recent examples include risk assessment of multiple pesticides and contaminants in humans and risk assessment of multiple pesticides in bees. In addition, new tools such as mathematical and biological models are being used to predict toxicity and detoxification. Scientists will continue to push back the boundaries to ensure that policies aimed at protecting consumers are based on the latest and most reliable science available.