BE values are not intended to be used for comparison with individual biomonitoring data. However, situations may arise in which a patient obtains data on levels of a chemical or chemicals in their body and brings these data to their health care provider, requesting interpretive information. The following is some advice that might help you discuss interpretation of his or her biomonitoring data. More detailed discussions of interpretation of biomonitoring data and communication regarding measured chemical concentrations and BE values are presented in the BE Communications Guidelines paper, available here.
Presence of a chemical does not imply disease
“The presence of a chemical does not imply disease. The levels or concentrations of the chemical are more important determinants of the relation to disease, when established in appropriate research studies, than the detection or presence of a chemical” (CDC, 2005). Just like the pharmacology arena, the dose of a chemical or level in the body dictates the degree of potential for health risks. If a patient takes too little of a prescribed drug, it may not have the intended effect (like taking 1/100th of an aspirin). If your patient takes too much of a prescribed drug, there may be unintended (adverse) consequences. The same holds true for the presence of chemicals in our bodies. There exists a dose and response relationship whereby the higher the dose (or concentration of chemical measured in your patient’s blood or urine) the higher the risks of health effects. Conversely, there is some level at which no response would be expected.
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Response to Patients
If a patient arrives with biomonitoring data that they have obtained themselves, it is important to understand that such data may not be analytically reliable. The analytical methods for detection and quantitation of trace levels of environmental chemicals are complex, and few laboratories are qualified to provide valid, reliable results. Further conversation with your patient should address the following issues.
First, ask your patient an important question:
- Why did the patient obtain his or her biomonitoring data? Does the patient have a suspicion regarding the air or water at their place of residence due to odors, tastes, or a nearby facility? Is there an occupational exposure about which the patient is concerned? Such information will provide important context in evaluation of the biomonitoring data and may lead the physician to refer the patient to an occupational medicine specialist or to a local or state public health agency for additional information.
Second, compare your patient’s findings with levels measured in the general U.S. population:
- How does the level of a particular chemical measured in your patient compare with data for the general population? The Centers for Disease Control (CDC) is compiling significant databases of biomonitoring data that provide information on the concentrations of many chemicals in the general US population (www.cdc.gov/nceh). Such information is relevant for the interpretation of individual biomonitoring data. For example, if biomarker concentrations in a patient are substantially elevated over those generally found in the general population, further evaluation and investigation (beginning with a repeated measurement at an accredited and reputable laboratory) may be appropriate if those values also exceed the “low” priority BE range, perhaps in conjunction with local or state public health agencies or in conjunction with an occupational physician.
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How Can The Biomonitoring Equivalents Help You Advise Your Patient?
As discussed above, BE values in general are appropriate for screening of population-based biomonitoring data, but not for assessment of measured concentrations in individuals or for diagnosis of any condition. With that caveat in mind, physicians may find BE values useful in assisting patients with interpretation of biomonitoring data that the individual obtains independently or with concerns about media reports of biomonitoring results. Detailed patient guidance for particular chemicals must, by definition, be chemical-specific. Nonetheless, a number of important generalizations can be made regarding advice which is likely to be appropriate for individuals or groups with a biomonitored level of a chemical in the low, medium, or high priority ranges as presented in the chemical-specific BE page for that chemical (see graphic for general presentation of BE values and access chemical-specific BE information here).
Individuals with levels in this range have biomarker concentrations consistent with exposures at or below existing exposure guidance values. For these individuals, risk attributable to the exposure is negligible to zero (i.e., for threshold effects they are far below threshold), and specific advice regarding the exposure itself or regarding risk mitigation related to the exposure is not warranted. The primary role of the health care provider is to provide context and reassurance.
Individuals in this category have biomonitoring levels higher than those in the Low Priority category, but are generally below levels that are expected to be associated with adverse effects in humans. For such individuals, two types of advice may be appropriate. First, they might be provided with chemical-specific, practical advice regarding actions they may take in order to reduce exposure, if such information is available and the actions are reasonable. It is not clear that such action is necessarily warranted or beneficial; nonetheless, this may afford the individual a modicum of choice and an opportunity for control of exposure. Second, if there are multifactorial health endpoints of concern with a particular chemical, the patient might be advised as to lifestyle or other changes that might mitigate risk. For example, if cardiovascular disease is an endpoint of concern for a particular compound, it may be helpful to point out that via exercise, addressing cholesterol issues if necessary, and managing blood pressure, they may compensate for some small degree of risk attributable to chemical exposure.
In this category, it is essential to properly advise the patient as to what, precisely, a “high priority” for risk assessment follow-up means in the context of a particular chemical and the likelihood that effects will occur in humans. This is especially important with cancer endpoints, as a high public health priority indicates only that a theoretical 1:10,000 cancer risk has been exceeded. The overall risk of cancer mortality (not necessarily specific cancers of concern for the chemical at hand) is influenced by many different exposures and risk factors for cancer overall can be mitigated to a far greater degree by recognized health practices such as colonoscopy. Within this category, there are again three types of advice that might be given.
- First, immediate re-testing should be conducted to determine whether the measurement represents a repeatable level.
- Second, specific instruction for reduction in exposure may be appropriate if this can be achieved with practical interventions. The utility and practicality of this type of intervention is dependent upon routes and sources of exposure and by many other factors, and must be determined on a case-by-case basis.
- Third, there may be utility in screening for particular medical conditions either on a one-time or ongoing basis so that early intervention can be provided. However, such screening is probably warranted only for compounds that are not highly transient in the human body, when adverse human health effects have been clearly linked to the chemical, and when appropriate screening tests exist. For example, elevated cadmium biomarker concentrations might suggest screening tests for kidney function, because elevated cadmium exposure is linked with such responses in humans and cadmium is relatively persistent in the body. However, a one-time measurement of a blood chloroform concentration in the “high priority” range is unlikely to be informative either of long term exposure or of a specific health outcome that could be effectively evaluated through the use of screening tests, since chloroform is highly transient in blood and the BE value is based on subtle liver toxicity in a dog study.
Finally, it may be appropriate to refer a patient with a repeated measurement in the high priority range to a medical toxicologist. More information on this specialty can be found through the American College of Medical Toxicologists.
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Communicating with Patients Regarding Biomonitoring Data
Cholesterol provides a useful analogy for interpreting exceedances of BEs. While it is an endogenous substance and not an environmental chemical, the public is generally aware that cholesterol is present in the body and that cholesterol can be used as a biomarker for potential health risks. Further, a discussion of cholesterol can be used to bring forth to the public underlying concepts that are transferable to environmental chemicals - such as “dose-response” and “acceptable” or “normal” levels. People generally understand that there is a “dose-response” relationship between increasing blood cholesterol and the risk of heart disease (i.e., while high cholesterol levels are a risk factor for coronary heart disease (CHD), elevated levels do not mean that CHD is inevitable, but rather that the risk of CHD is greater). They also understand that the range of “normal” values may change over time as new knowledge is developed. People further understand individual variability, in that not everyone with a high fat diet has high cholesterol levels. Thus, a generic description of blood cholesterol may be a valuable tool for communicating information about biomonitoring levels exceeding the BE.
Further information regarding communication with the public on biomonitoring data may be found at www.biomonitoringinfo.org