Biomonitoring
In analytical chemistry, biomonitoring is the measurement of the body burden of toxic chemical compounds, elements, or their metabolites, in biological substances.[1][2] Often, these measurements are done in blood and urine.[3] Biomonitoring is performed in both environmental health, and in occupational safety and health as a means of exposure assessment and workplace health surveillance.
The two best established environmental biomonitoring programs in representative samples of the general population are those of the United States and Germany, although population-based programs exist in a few other countries.[4] In 2001, the U.S. Centers for Disease Control and Prevention (CDC) began to publish its biennial National Report on Human Exposure to Environmental Chemicals, which reports a statistically representative sample of the U.S. population.[5]
Overview
[edit]Biomonitoring involves the use of organisms to assess environmental contamination, such as of surrounding air or water. It can be done qualitatively by observing and noting changes in organisms, or quantitatively by measuring accumulation of chemicals in organism tissues. By observing or measuring the effects the environment has on its resident organisms, pollution may be suspected or inferred.[6]
Historically, public health regulations have been based on theoretical risk calculations according to known levels of chemical substances in air, water, soil, food, other consumer products and other sources of potential exposure.[citation needed] Human biomonitoring offers the opportunity to analyze the actual internal levels of bodily substances from all potential routes of exposure at one time, which may contribute to improving risk assessments.[7][better source needed]
Scientific advancements have made it possible to detect a greater number of chemical substances in smaller concentrations in the body, with some chemicals detectable at levels as low as parts per trillion.[8][better source needed] A single biomonitoring measurement is only one snapshot in time and may not accurately reflect the level of exposure over longer periods.[9]
The presence of an environmental chemical in the body does not necessarily indicate harm.[10] The analytical chemistry of detecting chemicals has advanced more rapidly than the ability to interpret the potential health consequences.[11] Health risks are usually established from toxicity studies in laboratory animals and epidemiological evidence in humans. Lead is a well studied chemical with a CDC action level of concern, currently at 10 μg/dL, or 100 parts per billion, in blood; however, neurobehavioral impairment has been noted below this level.[12] Because this approach requires establishment of cause and effect in epidemiological studies and a thorough understanding of human dose response, data to support these types of action levels exist for only a few environmental chemicals. The concept of Biomonitoring Equivalents (BEs) has been developed as an alternative approach to aid in interpreting and communicating biomonitoring results in the context of potential risks to health.[13]
There are different types of biomarkers that indicate exposure, effect, or susceptibility.[14]
Methodology
[edit]Chemicals and their metabolites can be detected in a variety of biological substances such as blood, urine, exhaled air, hair, nails, feces, semen, breast milk, or saliva.[15][14] Blood and urine are the most commonly used in occupational safety and health.[14]
Breast milk is a favored matrix (substance) to measure lipophilic (fat-loving) persistent, bioaccumulative, and toxic (PBT) compounds during lactation; this exposure route is dominant for breastfeeding children.[16] A lipophilic compound might also be detected in blood, while a hydrophilic (water-loving) compound might be detected in urine.[17]
Analytical methods used by the CDC include isotope dilution mass spectrometry, inductively coupled plasma mass spectrometry, or graphite furnace atomic absorption spectrometry.[17] Others include gas chromatography or high-performance liquid chromatography coupled with various detectors such as ultraviolet, electron capture, flame ionization, atomic emission, or mass spectrometric detectors. Ligand-binding assays and immunoassays are also used.[14]
As biomonitoring necessarily involves working with human subjects and specimens, biosafety procedures are necessary to prevent the transmission of pathogens.[14]
Biomonitoring equivalents
[edit]Scientists performing biomonitoring testing are able to detect and measure concentrations of natural and manmade chemicals in human blood and urine samples at parts-per-billion to parts-per-quadrillion levels. A 2006 U.S. National Research Council report found that while scientists were capable of detecting the chemicals at these levels, methods for interpreting and communicating what their presence meant regarding potential health risks to an individual or population were still lacking.[18] The report recommended that scientific research be done to improve the interpretation and communication of biomonitoring results through the use of existing risk assessments of specific chemicals.[18]
To address this situation, several groups recognized that exposure guidance values, such as reference dose and tolerable daily intake, could, with sufficient data, be translated into corresponding estimates of biomarker concentrations for use in the interpretation of biomonitoring data.[19][20] In 2007, the initial methodology for the systematic translation of exposure guidance values into corresponding screening values for biomonitoring data, dubbed Biomonitoring Equivalents, was published by scientists from Summit Toxicology.[20] Subsequently, an expert panel from government, industry and academia, convened to develop detailed guidelines for deriving and communicating these Biomonitoring Equivalents.[21]
Biomonitoring Equivalents can be used for evaluation of biomonitoring data in a risk assessment context. Comparing biomonitoring data for a chemical with its Biomonitoring Equivalent provides a means for assessing whether population exposures to chemicals are within or above the levels considered safe by regulatory agencies.[22] Biomonitoring Equivalents can thus assist scientists and risk managers in the prioritization of chemicals for follow-up or risk management activities.[20]
Since 2007, scientists have derived and published Biomonitoring Equivalents for more than 110 chemicals, including cadmium, benzene, chloroform, arsenic, toluene, methylene chloride, triclosan, dioxins, volatile organic compounds, and others.[23][24] Several have been developed through collaborations of scientists from the U.S. Environmental Protection Agency, CDC and Health Canada.[21] Researchers from the German Human Biomonitoring Commission[25] have also proposed a concept for deriving screening values similar to Biomonitoring Equivalents.[24]
Communication
[edit]The National Research Council's 2006 report emphasized that accurate communication of results is essential for the proper use of biomonitoring surveys, but at the same time noted "there is no accepted standard for good biomonitoring communications".[11] In 2007, the Boston University School of Public Health organized a panel on this topic.[26]
An expert panel on Biomonitoring Equivalents has published guidelines for communicating information to the general public and health care providers.[27]
Charles McKay of the Connecticut Poison Control Center is interviewed in a video titled "A Medical Doctor's Perspective on Biomonitoring", which is focused on helping the general public better understand biomonitoring.[28]