Biomarkers of exposure assessment

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Biomarkers in analytical chemistry and in environmental science are chemicals, metabolites, susceptibility characteristics, or changes in the body that relate to the exposure of an organism to a chemical. They have the ability to identify if an exposure has occurred, the route of exposure, the pathway of exposure, and the resulting effects of the exposure. The use of biomarkers in exposure studies is also referred to as biomonitoring. When dealing with exposure assessment, there are three types of biomarkers that can be useful, biomarkers of susceptibility, biomarkers of exposure, and biomarkers of effect. Biomarkers of exposure are the most widely used because they can provide information on the route, pathway, and sometimes, even the source of exposure.

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Biomarkers of susceptibility

Biomarkers of susceptibility are indicators of the natural characteristics of an organism that make it more susceptible to the effects of an exposure to a chemical. They can help define what sensitivities are more susceptible as well as critical times when exposures can be most detrimental. For example, the exhalation strength of an asthmatic will indicate how susceptible that person would be to the respiratory effects of exposure to brevetoxin, the toxic compound produced during a red tide.

Biomarkers of exposure

Biomarkers of exposure are the actual chemicals, or chemical metabolites, that can be measured in the body or after excretion from the body to determine different characteristics of an organism’s exposure. For example, a person or fish’s blood can be tested to see the levels of lead and therefore determine the exposure.

Biomarkers of effect

Biomarkers of effect are the quantifiable changes that an individual endures, which indicates an exposure to a compound and may indicate a resulting health effect. For example, after exposure to DDT, an organochlorine insecticide known to cause problems in the reproductive system, a woman may experience miscarriages, which can be linked to her previous exposure.

Biomarkers of exposure are the most widely used because they can provide information on the route, pathway, and sometimes, even the source of exposure. These indicators also allow researchers to work forward in time to determine an exposure, and prevent it from causing further damage. This is unlike biomarkers of effect, in which a scientist may work backwards to determine if and what kind of exposure took place, but may be too late to change anything. However, biomarkers of effect are useful for future studies on the chemical(s) of interest and the results may aid in stricter laws or guidelines regarding the chemical(s).

Biomarkers must be evaluated in terms of their ability to predict and quantify exposure and dose. There are certain properties that are desirable when linking a biomarker with an exposure. These include high specificity (one exposure to one biomarker), linear relationship across time, strong correlation with a health effect, inexpensive study, and consistency (the same exposure will produce the same concentration of the biomarker every time). Without these ideal characteristics, the use of biomarkers as a strong predictor of exposure has limitations.

Many different classes of compounds can be measured in different tissues and parts of the body. From breath to hair to saliva, almost every tissue in the body has been tested as a biomarker of exposure and almost every major environmental pollutant can be identified by biomarkers, including volatile organic chemicals (VOCs) and metals like arsenic or lead. It all depends on the chemical structures and reactivity of the compound with the makeup of its storage space. The following table identifies major environmental pollutants and their biomarker tissue or organ [1]

Pollutant GroupParent CompoundMetabolite
VOCsBreath, bloodBlood, urine
TetrachoroethyleneBreath, blood, mothers' milkNone
SVOCs (pesticides, PCBs, PAHs, dioxins/furans Blood, fat, mothers' milkBlood, urine
MetalsBlood, bone, hair, cord blood, placenta, feces
Carbon monoxide Breath, bloodBlood (carboxyhemoglobin)
Environmental Tobacco Smoke (ETS)Breath (2,5-dimethylfuran) [2] [3] Saliva, blood (cotinine)

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Toxicity Degree of harmfulness of substances

Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell (cytotoxicity) or an organ such as the liver (hepatotoxicity). By extension, the word may be metaphorically used to describe toxic effects on larger and more complex groups, such as the family unit or society at large. Sometimes the word is more or less synonymous with poisoning in everyday usage.

Chlordane, or chlordan, was an organochlorine compound used as a pesticide. It is a white solid. In the United States, chlordane was used for termite-treatment of approximately 30 million homes until it was banned in 1988. Chlordane was banned 10 years earlier for food crops like corn and citrus, and on lawns and domestic gardens.

Volatile organic compounds (VOC) are organic chemicals that have a high vapour pressure at room temperature. High vapor pressure correlates with a low boiling point, which relates to the number of the sample's molecules in the surrounding air, a trait known as volatility.

Aquatic toxicology

Aquatic toxicology is the study of the effects of manufactured chemicals and other anthropogenic and natural materials and activities on aquatic organisms at various levels of organization, from subcellular through individual organisms to communities and ecosystems. Aquatic toxicology is a multidisciplinary field which integrates toxicology, aquatic ecology and aquatic chemistry.

Toxicokinetics is the description of both what rate a chemical will enter the body and what occurs to excrete and metabolize the compound once it is in the body.

Persistent organic pollutant Organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes

Persistent organic pollutants (POPs), sometimes known as "forever chemicals" are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. It is a toxic chemical that adversely affect human health and the environment around the world. Because they can be transported by wind and water, most POPs generated in one country can and do affect people and wildlife far from where they are used and released. The effect of POPs on human and environmental health was discussed, with intention to eliminate or severely restrict their production, by the international community at the Stockholm Convention on Persistent Organic Pollutants in 2001. The United States has taken strong domestic action to reduce emissions of POPs. For example, none of the original POPs pesticides listed in the Stockholm Convention is registered for sale and distribution in the United States today and in 1978, Congress prohibited the manufacture of PCBs and severely restricted the use of remaining PCB stocks. In addition, since 1987, EPA and the states have effectively reduced environmental releases of dioxins and furans to land, air, and water from U.S. sources.

Bioindicator Indicator species that can be used to reveal the qualitative status of an environment

A bioindicator is any species or group of species whose function, population, or status can reveal the qualitative status of the environment. For example, copepods and other small water crustaceans that are present in many water bodies can be monitored for changes that may indicate a problem within their ecosystem. Bioindicators can tell us about the cumulative effects of different pollutants in the ecosystem and about how long a problem may have been present, which physical and chemical testing cannot.

Benzyl butyl phthalate Chemical compound

Benzyl butyl phthalate (BBP) is a phthalate, an ester of phthalic acid, benzyl alcohol, and n-butanol. BBP is a clear liquid with the chemical formula C19H20O4. It was mostly used as a plasticizer for PVC. It is considered a toxicant.

Endrin Chemical compound

Endrin is an organochloride with the chemical formula C12H8Cl6O that was first produced in 1950 by Shell and Velsicol Chemical Corporation. It was primarily used as an insecticide, as well as a rodenticide and piscicide. It is a colourless, odorless solid, although commercial samples are often off-white. Endrin was manufactured as an emulsifiable solution known commercially as Endrex. The compound became infamous as a persistent organic pollutant and for this reason it is banned in many countries.

In biomedical contexts, a biomarker, or biological marker is a measurable indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. Biomarkers are used in many scientific fields.


Exposure assessment is a branch of environmental science and occupational hygiene that focuses on the processes that take place at the interface between the environment containing the contaminant of interest and the organism being considered. These are the final steps in the path to release an environmental contaminant, through transport to its effect in a biological system. It tries to measure how much of a contaminant can be absorbed by an exposed target organism, in what form, at what rate and how much of the absorbed amount is actually available to produce a biological effect. Although the same general concepts apply to other organisms, the overwhelming majority of applications of exposure assessment are concerned with human health, making it an important tool in public health.

Sentinel species Organisms used to detect risks to humans by providing advance warning of a danger

Sentinel species are organisms, often animals, used to detect risks to humans by providing advance warning of a danger. The terms primarily apply in the context of environmental hazards rather than those from other sources. Some animals can act as sentinels because they may be more susceptible or have greater exposure to a particular hazard than humans in the same environment. People have long observed animals for signs of impending hazards or evidence of environmental threats. Plants and other living organisms have also been used for these purposes.

Environmental toxicology

Environmental toxicology is a multidisciplinary field of science concerned with the study of the harmful effects of various chemical, biological and physical agents on living organisms. Ecotoxicology is a subdiscipline of environmental toxicology concerned with studying the harmful effects of toxicants at the population and ecosystem levels.

Hexachlorocyclopentadiene Chemical compound

Hexachlorocyclopentadiene (HCCPD), also known as C-56, Graphlox, and HRS 1655, is an organochlorine compound with the formula C5Cl6. It is a precursor to pesticides, flame retardants, and dyes. It is a colourless liquid, although commercial samples appear lemon-yellow liquid sometimes with a bluish vapour. Many of its derivatives proved to be highly controversial, as studies showed them to be persistent organic pollutants. An estimated 270,000 tons were produced until 1976, and smaller amounts continue to be produced today. Two prominent manufacturers are Velsicol Chemical Corporation in the US and by Jiangsu Anpon Electrochemicals Co. in China.

In analytical chemistry, biomonitoring is the measurement of the body burden of toxic chemical compounds, elements, or their metabolites, in biological substances. Often, these measurements are done in blood and urine. Biomonitoring is performed in both environmental health, and in occupational safety and health as a means of exposure assessment and workplace health surveillance.

Inhalation is a major route of exposure that occurs when an individual breathes in polluted air which enters the respiratory tract. Identification of the pollutant uptake by the respiratory system can determine how the resulting exposure contributes to the dose. In this way, the mechanism of pollutant uptake by the respiratory system can be used to predict potential health impacts within the human population.

Terbufos Chemical compound

Terbufos is a chemical compound used in insecticides and nematicides. Terbufos is part of the chemical family of organophosphates. It is a clear, colourless to pale yellow or reddish-brown liquid and sold commercially as granulate.

Tissue residue is the concentration of a chemical or compound in an organism's tissue or in a portion of an organism's tissue. Tissue residue is used in aquatic toxicology to help determine the fate of chemicals in aquatic systems, bioaccumulation of a substance, or bioavailability of a substance, account for multiple routes of exposure, and address an organism's exposure to chemical mixtures. A tissue residue approach to toxicity testing is considered a more direct and less variable measure of chemical exposure and is less dependent on external environmental factors than measuring the concentration of a chemical in the exposure media.

Occupational toxicology is the application of toxicology to chemical hazards in the workplace. It focuses on substances and conditions that occur in workplaces, where inhalation exposure and dermal exposure are most important, there is often exposure to mixtures of chemicals whose interactions are complex, health effects are influenced or confounded by other environmental and individual factors, and there is a focus on identifying early adverse affects that are more subtle than those presented in clinical medicine.

Anne C. Steinemann American civil and environmental engineering academic

Anne C. Steinemann is an American civil and environmental engineering academic who has specialized chiefly in the fields of "healthy built environments, indoor air quality, consumer product emissions and exposures, drought management, and climate-related hazards", with a focus on engineering and sustainability. Currently professor of civil engineering at the University of Melbourne and professor of engineering at James Cook University, she has also advised numerous government and industry bodies in the United States and Australia and appeared widely in press, radio, television and website segments communicating her findings to the general public.

References

  1. Ott, W. R., Steinemann, A. C., & Wallace, L. A. (2007). Biomarkers of exposure. In W. R. Ott, A. C. Steinemann & L. A. Wallace (Eds.), Exposure analysis (pp. 395-404). Boca Raton, FL: Taylor & Francis.
  2. Gordon S.M., Wallace L.A., Brinkman M.C., Callahan P.J., & Kenny D.V. (2002). Volatile organic compounds as breath biomarkers for active and passive smoking. Environ Health Perspect. 110(7):689-98.
  3. Perbellini L., Princivalle A., Cerpelloni M., Pasini F., & Brugnone F. (2003). Comparison of breath, blood and urine concentrations in the biomonitoring of environmental exposure to 1,3-butadiene, 2,5-dimethylfuran, and benzene. Int Arch Occup Environ Health. 76(6):461-6.