Poster
# 46
Poster |
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6th Internet World Congress for Biomedical Sciences |
Mariarosa Re(1)
(1)Dipart. Medicina Preventiva, Occupazionale e di Comunitą. University of Pavia - Pavia. Italy
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[Hygiene, Public Health & Preventive Medicine] |
[Occupational Health] |
Procedures for assessment of occupational exposure to hazardous chemicals through correlation-based methods may be applied to several working situations, such as: (a) mapping of concentrations around the emitting source of a chemical agent, as a function of distance from source; (b) classification of levels of exposure for different operations of the same job, involving use of the same chemicals; (c) evaluation of multiple exposure, resulting from use of mixtures of chemicals, so that the concentration in air of each substance is more or less significantly correlated with concentrations of all the other substances in the mixture.
Since interest in multiple exposure assessment has been increasing in recent years, this paper will analyse and discuss correlation-based procedures applicable to multiple exposure.
Epidemiological studies have shown that in many cases occupational risk cannot be ascribed to a single chemical hazard, but to simultaneous exposure to more or less complex mixtures of several chemicals (e.g. rubber production). Therefore, several studies have been reported (1-4) concerning multiple occupational exposure and its adverse effects on health as a result of toxicokinetic and toxicodynamic interactions of chemicals in the mixture. The following types of effects have been identified ( 3):
(a) additivity, i.e. the resulting effect is the sum of effects of individual hazards;
(b) potentiation, i.e. the effect of one chemical is increased by exposure to other chemicals that are only slightly active when alone;
(c) synergism, i.e. the effect of interactions is greater than that resulting purely from additivity;
(d) antagonism, i.e. interactions result in a decrease of toxicity, owing to interference of chemicals with each other.
Another important question to be considered (2,4) is possible potentiation of carcinogenic or allergic effects (for instance in occupational exposure to metals) that may be expected even at very low concentrations.
It has been reported (3) that potentiation effects are found more frequently than the other effects, and are worth being considered, in presence of mixtures, as capable of modifying the expected action of a single substance.
Additive effects are considered as criteria for establishing occupational exposure limits for mixtures by the American Conference of Governmental Industrial Hygienists (ACGIH) (5). ACGIH recommends that, in presence of two or more hazardous substances acting upon the same organ system, their combined effect should be considered, rather than the individual effects; these should be considered additive unless it is reasonable to believe that they are in reality independent. ACGIH also recommends that cases of synergistic or potentiating action must be considered singularly. Moreover, when multiple exposure is evaluated by measuring a single substance, its limit should be reduced by a suitable factor, as a function of number, toxicity and quantity of the other substances.
As already reported (2-4,6) the ideally correct procedure for multiple exposure assessment involves complete identification and quantification of each hazardous chemical. However, such a procedure is not easily applicable to workplaces and working situations for reasons of technical and economic feasibility. So, the traditional approach to multiple exposure assessment is to quantify only one component of the mixture. As an alternative to the traditional approach, a more accurate and reliable estimate of multiple exposure may be obtained through correlation-based procedures, described in the following section.
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[Hygiene, Public Health & Preventive Medicine] |
[Occupational Health] |
