Health-relevant exposure, defined

Considering pesticide exposure in the context of epidemiological investigations involves the evaluation of exposures that are relevant to health. Exposure is usually defined as contact with an agent and can be contrasted with absorbed dose, the amount that enters or interacts with the organism. The concept of health-relevant exposure implies that not all exposures lead to, or are associated with, a certain health risk. 

The LOQ must take into account relevant health based limit values or relevant exposure levels. In SANCO/825/00 a method to calculate a relevant health based limit is given. The limit of quantitation must be equal to or lower than the concentration C, which is defined by equation (1). 

Hypothetical or potenhal causalities include postulated causalities which have not yet been proven to be related to IAQ. An example is multiple chemical sensitivity (MCS). Often effects or exposures cannot be quantified, not even by indicators. Toxicological evaluations can only deal with effects and exposures which are quantifiable. Therefore, these undocumented causalities must be defined as hypothetical or potential causalities. Even if some of these effects may be considered adverse or have high prevalence, the present level of knowledge prohibits an official rational preventive action and no official guidelines or recommendations can be established. It should be noted that all new types of IAQ problems start as hypothetical. This group includes many health effects which are potentially important to human health and thus defines the research forefront in IAQ sciences. Table 14.2 shows some examples. Several potential or hypothetical causalities are discussed in the scientific literature. Their relevance to health indoors is unknown and no official recommendations or guidance can be established. Mitigation of indoor climate problems becomes a matter of ad hoc solutions and a major... 

The following categories of data needs have been identified by a joint team of scientists from ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that, if known, would reduce or eliminate the uncertainties of human health assessment. Each data need discussion highlights the availability, or absence, of the relevant exposure information. A statement that reflects the importance of identified data needs is also included. In the future, these data needs will be evaluated and prioritized, and a substance-specific research agenda will be proposed. 

An important outcome of the JECFA evaluation is the establishment of an ADI for a food additive. The ADI is based on the available toxicological data and the no adverse effect level in the relevant species. JECFA defines the ADI as an estimate of the amount of a food additive, expressed on a body weight basis, that can be ingested daily over a lifetime without appreciable health risk (8). JECFA utilizes animal data to determine the ADI based on the highest no-observed-adverse-effect level (NOAEL), and a safety factor is applied to the NOAEL to provide a margin of safety when extrapolating animal data to humans. JECFA typically uses safety factors of 50, 100, or 200 in the determination of an ADI. The NOAEL is divided by the safety factor to calculate the ADI. The food additive is considered safe for its intended use if the human exposure does not exceed the ADI on a chronic basis. This type of information may potentially be used to help assess the safety of a pharmaceutical excipient that is also used as a food additive, based on a comparison of the ADI to the estimated daily intake of the excipient. 

The potential for non-carcinogenic health effects associated with exposure of local residents to POPs in locally consumed food items and the ambient air was evaluated by calculating the relevant HQ for individual POPs. The HQ was defined as the ratio of the estimated lifetime average daily dose (LADD) of POPs from dietary (Table 7.6) and inhalation... 

Chemical risk assessment is a means to contain such conflicts. It defines a series of relevant endpoints and exposure processes in the world that we will accept as relevant, while others (such as changing property relations) are not. The boundary between risk assessment and risk regulation is not just a boundary that keeps dirty politics out of disinterested science, but also a boundary that prevents new concerns from making the assessment process unpredictable, for applicants, policy makers, as well as environmentalists. Such new concerns can be new health or environmental... 

For individual constituents of drinking-water, health-based targets are established. These targets represent a health risk from long-term exposure, in a situation where fluctuations in concentration are small or occur over long periods, It is important that such targets are defined by the relevant local authority, are realistic under local operating conditions and are set to protect and improve public health,... 

In general, criteria developed to protect against noncancer effects are based on the assumption that there is a threshold below which no adverse health effects will occur. A critical evaluation of available human health and animal toxicity studies is performed to identify the most sensitive adverse effect relevant to humans. Noncancer exposure criteria are often based on an experimentally defined dose at which no adverse effects were observed (i.e., the no-observed-adverse-effect level - NOAEL). If no adequate NOAEL is available, the lowest dose at which adverse effects were observed (lowest-observed-adverse-effect level - LOAEL) is used. Another commonly used approach is to fit study data to dose-response models to identify appropriate values (e.g., dose corresponding to the upper bound of the 10% response level or BMDLio) as the basis for deriving the exposure criteria. 

The potential for unusual health effects of chemical mixtures due to the interaction of chemicals or their metabolites (e.g., metabolites of trichloroethylene and benzene) in or with the biosystem constitutes a real issue in the public health arena. However, toxicity testing to predict effects on humans has traditionally studied one chemical at a time for various reasons convenient to handle, physiochemical properties readily defined, dosage could easily be controlled, biologic fate could easily be measured, and relevant data were often available from human occupational exposures. Chemicals are known to cause disease for example, arsenic and skin cancer, asbestos and lung cancer, lead and decrements of IQ, and hepatitis B predisposes to aflatoxin-induced liver cancer but the link between the extent of human exposure to even well-defined chemical mixtures and disease formation remains relatively unexplored, but of paramount importance to public health. 

Tables 6-1 and 6-2 summarize the suggested fraction-specific MRLs for inhalation and oral exposure. These fraction-specific MRLs are provisional values, reflecting the uncertainty inherent in this approach (see Section 6.6.2 for a more complete discussion). As with any ATSDR MRL, the MRLs in Tables 6-1 and 6-2 are intended to serve as health guidance values and are not to be used to define clean-up or action levels. Information listed in brackets in Table 6-2 is from sources other than ATSDR toxicological profiles. This information indicates potentially sensitive end points but does not have the same level of confidence as information from the ATSDR toxicological profiles. Additional details and tables listing all the candidate MRLs and relevant cancer assessments are presented in Section 6.6.2. Chapter 7 also...

The WHO definition of VOCs refers to the behavior of the compounds in traditional analytical procedures and not to their ability to cause discomfort and health effects through environmental exposures. Also, some organic compounds outside the VOC range as defined by WHO may contribute to relevant sensory effects. Consequently, the organic compounds relevant to the TVOC concept from the toxicologist s point of view may not be defined strictly by the WHO definition. However, no exact definition of the relevant compounds can be made at present. The pragmatic short cut suggested by... 

Relevant threshold limit values for terpenes are rare because of a lack of basic information about specific terpene products and by-products on the one hand, and occupational and environmental exposures on the other hand. The threshold limit values which have been documented the best concern oil of turpentine. A MAK-value of 100 ppm is defined in German regulations and noted to be dermally sensitive. For other terpenes, such as d-limonene which is also classified as dermally sensitive, it has not yet been possible to establish a MAK-value because of a lack of information of their effects on animals or humans. With terpenes, as is often the case, aggregate concentration parameters are used as limit values such as the minimum level goals recommended by the former German Federal Health Authority. These suggested minimum values bear in mind actual levels detected in indoor areas. 

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