General Introduction to biomonitoring

This page provides information about biomonitoring and how it can help us to assess our exposure to chemicals

• Human exposure to Chemicals
• Assessing exposure and uptake of chemicals
• The applications of human biomonitoring
• International biomonitoring programmes

 

Human exposure to chemicals

We are all exposed in or our daily lives to a range of different chemical elements and chemical compounds, some naturally occurring, others of anthropogenic (man-made) origin, some potentially hazardous to health, others relatively harmless. Exposure can occur if a person works with chemicals (occupational exposure) or can occur during daily life, via three main exposure routes - the skin (dermal exposure), the lungs (following inhalation) and the gut wall (following ingestion) - and from numerous sources e.g. food and water, air and dust, consumer products, chemical incidents (accidents, intentional releases).

Traditionally, environmental monitoring has consisted of measuring levels of chemicals in air, soil and water. This is useful as it tells us what is in the environment and provides us with an indication of what people could potentially be exposed but it does not tell us what people are actually exposed to and can therefore only be used to estimate possible exposure. Human biomonitoring however, when appropriate, can provide information on exposure and uptake by the individual being studied. It therefore provides better data than environmental monitoring.

Before considering HBM, it is appropriate to consider what happens to the chemical once it enters the body and this is dependent on its chemical and physical properties and the capacity of the body to break down and eliminate it. Of crucial importance in HBM studies is the length of time a chemical remains in the body and how rapidly it is excreted. This governs when samples need to be taken and indeed whether biomonitoring is appropriate or not in a given situation.

Chemicals can be transported from their point of entry to other parts of the body (via the bloodstream), metabolised or "detoxified" by the liver into a different form and then excreted (in the urine, faeces and to a lesser extent in sweat and even hair). Others that cannot be metabolised and/or excreted can be stored in other tissues or organs, such as in adipose (fat) tissue or the liver. Some chemicals can also be mobilised from fat stores during pregnancy and appear in breast milk.

Biomonitoring is the sampling of blood, urine, breast milk, fat, hair and other tissues to assess human exposure and uptake of natural and synthetic chemicals. It provides an integrated measure of exposure from all environmental sources (air, water, food etc) and exposure routes (dermal, inhalation, ingestion).

A Biomarker is a chemical, biochemical, or functional indicator of exposure to and uptake of (or the effect of exposure to) an environmental chemical, physical or biological agent. (i.e. changes in cells or biochemical pathways that indicate that a chemical has been present and interacted with the body's systems).

 

Assessing exposure and uptake of chemicals

To assess exposure and uptake, the presence of the chemical and/or its metabolites (break down products) in samples of tissues (e.g. fat), bodily fluids (e.g. blood) or waste products (e.g. urine) can be determined. These are known as "biomarkers of exposure". Some chemicals might not be detectable themselves but their effects on the body's processes can be measured. For example, measuring the activity of the enzyme acetylcholinesterase is a good indicator of exposure to organophosphate pesticides, as this enzyme is prevented from working properly (inhibited) by this group of chemicals. The degree of inhibition is positively related to the degree of exposure. Such a marker is known as a "biomarker of exposure/effect".

 

The applications of human biomonitoring

Measuring people's exposure to chemicals, many of which have hazardous properties, provides information on potential risks to health. Biomonitoring is therefore of importance to public health professionals, government departments and agencies as well as industry.

Biomonitoring has been used for some time by industry, in order to ensure the health of their employees is not being compromised by exposure to certain chemicals in the workplace. Monitoring of exposure to chemicals in occupational settings is also carried out/required by law to ensure that legislative exposure limits are not exceeded. But biomonitoring is now being used in different applications. For example, it can be used to establish the "background" range of exposure to a chemical in the general population - in other words, establish what is "normal" - to allow individuals or sub-populations that differ significantly from the norm to be identified and for future biomonitoring data to be put into context. To this end, the Reference Range study has been set up as part of the HPA biomonitoring work.

Biomonitoring can also be used to detect exposure patterns and trends, both temporally (over time) and spatially (between locations) i.e. to see if exposure is increasing or decreasing from one year to the next, or if exposure differs between people living in different geographical areas of the UK. Biomonitoring can also be used to measure the effectiveness of control measures aimed at reducing or eliminating exposure e.g. lead in paint, toys, water pipes and petrol. Biomonitoring data, if combined with data on health effects, can be used to correlate exposure with health effects observed in populations. At present, however, such work is difficult due to the limited amount of overlapping health and biomonitoring data available.

International biomonitoring programs

There are many ongoing biomonitoring programs, the most established of which is the National Biomonitoring Program (NBP)  run by the Environmental Health Laboratory of the Centers for Disease Control and Prevention (CDC) in the US. Health Canada, the federal department for health in Canada, runs a biomonitoring program, as does Umweltbundesamt, the German government's environment agency.

 

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Last reviewed: 12 July 2011