From pesticides in our food to hormone disruptors in our kitchen pans, modern life is saturated with chemicals, exposing us to unknown long-term health impacts.
One of the surest routes to quantifying these impacts is the scientific method of biomonitoring, which consists of measuring the concentration of chemicals in biological specimens such as blood, hair or breastmilk. These measurable indicators are known as biomarkers.
Currently, very few biomarkers are available to assess the impact of chemicals on human health, even though 10 million new substances are developed and introduced to the market each year.
My research aims to bridge this gap by identifying new biomarkers of chemicals of emerging concern in order to assess their health effects.
What makes a good biomarker
One of the difficulties of biomonitoring is that once absorbed in our bodies, chemical pollutants are typically processed into one or more breakdown substances, known as metabolites. As a result, many chemicals go under the radar.
In order to understand what happens to a chemical once it has entered a living organism, researchers can use various techniques, including approaches based on computer modelling (in silico models), tests carried out on cell cultures (in vitro approaches), and animal tests (in vivo) to identify potential biomarkers.
The challenge is to find biomarkers that allow us to draw a link between contamination by a toxic chemical and the potential health effects. These biomarkers may be the toxic product itself or the metabolites left in its wake.
But what is a “good” biomarker? In order to be effective in human biomonitoring, it must meet several criteria.
First, it should directly reflect the type of chemical to which people are exposed. This means it must be a direct product of the chemical and help pinpoint the level of exposure to it.
Second, a good biomarker should be stable enough to be detectable in the body for a sufficient period without further metabolization. This stability ensures that the biomarker can be measured reliably in biological samples, thus providing an accurate assessment of exposure levels.
Third, a good biomarker should enable precise evaluation. It must be specific to the chemical of interest without interference from other substances. This specificity is critical for accurately interpreting biomonitoring data and making informed decisions about health risks and regulatory measures.
A weekly e-mail in English featuring expertise from scholars and researchers. It provides an introduction to the diversity of research coming out of the continent and considers some of the key issues facing European countries. Get the newsletter!
Two examples of ‘bad’ biomarkers
One example of a “bad” biomarker involves the diester metabolites of organophosphate esters. These compounds are high-production-volume chemicals widely used in household products as flame retardants and plasticizers, and are suspected to have adverse effects on the environment and human health.
Recent findings showed the coexistence of both organophosphate esters and their diester metabolites in the environment. This indicates that the use of diesters as biomarkers to estimate human contamination by organophosphate esters leads to an overestimation.
Using an inappropriate biomarker may also lead to an underestimation of the concentration of a compound. An example relates to chlorinated paraffins, persistent organic pollutants that are also used as flame retardants in household products. In biomonitoring, researchers use the original form of chlorinated paraffins due to their persistence in humans. However, their levels in human samples are much lower than those in the environment, which seems to indicate underestimation in human biomonitoring.
Recently, my team has found the potential for biodegradation of chlorinated paraffins. This could explain the difference between measurements taken in the environment and those taken in living organisms. We are currently working on the identification of appropriate biomarkers of these chemicals.
Current limitations in human biomonitoring
Despite the critical importance of biomarkers, several limitations hinder their effective use in human biomonitoring.
A significant challenge is the limited number of human biomarkers available compared to the vast number of chemicals we are exposed to daily. Existing biomonitoring programmes designed to assess contamination in humans are only capable of tracking a few hundred biomarkers at best, a small fraction of the tens of thousands of markers that environmental monitoring programmes use to report pollution.
Moreover, humans are exposed to a cocktail of chemicals daily, enhancing their adverse effects and complicating the assessment of cumulative effects. The pathways of exposure, such as inhalation, ingestion and dermal contact, add another layer of complexity.
Another limitation of current biomarkers is the reliance on extrapolation from in vitro and in vivo models to human contexts. While these models provide valuable insights, they do not always accurately reflect human metabolism and exposure scenarios, leading to uncertainties in risk assessment and management.
To address these challenges, my research aims to establish a workflow for the systematic identification and quantification of chemical biomarkers. The goal is to improve the accuracy and applicability of biomonitoring in terms of human health.
Innovative approaches in biomarker research
We aim to develop a framework for biomarker identification that could be used to ensure that newly identified biomarkers are relevant, stable and specific.
This framework includes advanced sampling methods, state-of-the-art analytical techniques, and robust systems for data interpretation. For instance, by combining advanced chromatographic techniques, which enable the various components of a biological sample to be separated very efficiently, with highly accurate methods of analysis (high-resolution mass spectrometry), we can detect and quantify biomarkers with greater sensitivity and specificity.
This allows for the identification of previously undetectable or poorly understood biomarkers, expanding the scope of human biomonitoring.
Additionally, the development of standardized protocols for sample collection and analysis ensures consistency and reliability across different studies and monitoring programmes, which is crucial for comparing data and drawing meaningful conclusions about exposure trends and health risks.
This multidisciplinary approach will hopefully be providing a more comprehensive understanding of human exposure to hazardous chemicals. This new data could form a basis for improving prevention and adapting regulations in order to limit harmful exposure.
Created in 2007 to help accelerate and share scientific knowledge on key societal issues, the Axa Research Fund has supported nearly 700 projects around the world conducted by researchers in 38 countries. To learn more, visit the website of the Axa Research Fund or follow @AXAResearchFund on X.
