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| NIOSH Home > Safety and Health Topics >Skin Exposures and Effects >Occupational & Environmental Exposures of Skin to Chemicals- 2005> Abstracts |
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Methodology for the evaluation of occupational skin exposure
G. Maina*1, F. Larese Filon2, P. Sartorelli3, M. Manzari1, M.G. Andreoni1 Background
The attention internationally paid to dermal absorption of chemicals in the last few years has highlighted the number of problems connected with this topic. Reliable methods are today used in risk assessment of exposure to chemicals absorbed by inhalation, but many difficulties concern dermal exposure assessment and some more in the evaluation of the process of skin contamination. Concentrating the attention on dermal exposure quantification, the instruments today offered by Industrial Hygiene are unsatisfactory in occupational settings: the methods used to this purpose – methods of skin substitutes, removal methods, methods with fluorescent tracers – lack quantification accuracy and are difficult to be correctly interpreted. These sampling strategies (concerning duration of exposure, place and time) usually comply with the researcher’s specific interest, but are not founded on established standards. Further limits appear when the results of exposure quantification are compared with the related dermal occupational exposure limits (DOELs), which are today available for a restricted number of chemicals. To solve these problems some conceptual models have been proposed: starting from theoretical assumptions, they make use of information about chemical-physical characteristics of substances and experimental data to asses dermal absorption. These predictable models (Quantitative Structure - Activity Relationship models QSARs) cannot be practically used in risk assessment because they are not completely reliable and because they are available only for few chemicals. In occupational settings, especially in small and medium-sized enterprises, skin contamination and consequent dermal absorption risk must be assessed in a simply easy way in order to be able to identify the risk in the work-place. To provide a useful method for chemical risk assessment, the authors, using their experience gained while attending Dermal Exposure Network, working on European research projects RISKOFDERM and EDETOX and on the basis of literature data, have proposed a simplified check-list, easy to be used by a medical expert or by any observer trained in accurate assessment of occupational skin contamination. The check-list aims are: (1) to propose a simplified method to evaluate skin contamination; (2) to calculate hazard according to selected parameters (basic features of the chemical and of the exposure) identified by means of literature data; (3) to determinate intervention priorities and evaluate their effectiveness. Methods
The check-list consists of three steps which identify the fundamental phases of the method (Figure 1): 1. Dermal contamination risk evaluation present in the job taken into consideration. 2. Chemical hazard evaluation. 3. Exposure time.
The first step consists of five sections, each of them focusing the attention on an element responsible for contamination risk: working conditions, use of protective devices, skin contamination directly observed, worker’s personal cleanliness, workplace. Each section contains a number of items which explore the contribution of different variables: i.e. the formation of solid particles, and their size, the worker’s distance and use of tools are elements characterizing risk in section 1 (“working conditions”). Types of protective gloves, how long they are used and how often they are replaced are elements indicating the degree of protection offered by protective devices in section 2 (“PPE”); in section 4 (“worker”) how often and how correctly hands are washed or cleaned are elements indicating the worker’s personal cleanliness. Inside each section the items are grouped according to their function and are given a predetermined score based both on experience and on literature data. The second step (chemical hazard evaluation) contains items carefully organized in 3 groups: chemical-physical characteristics (physical state, solubility, boiling point if liquid), toxicological data (dermal DL50), R-phrases. All the relative information obtained from the safety data sheets of the chemicals used to carry out the job allows a weighted assessment based on the scores already defined in the previous step: in particular, the R-phrases classification is obtained from HSE model In this section the score given to R-phrases gains such crucial weight as to influence the result of the same section by over 80%: this happens because the intrinsic hazard of the chemical contaminant is very important. Since it is impossible and incorrect to quantify, as a first step, the contribution given to contamination assessment by each section, the arbitrary value 10 represent the maximum score that can be given to each of the six sections. Therefore, to obtain the final score of each section, it was agreed that the effective result obtained from the sum of the different items in each section should be referred to that arbitrary value; consequently the score of each section ranges from 1 to 10. The observer, after reading and recording the scores (first step) often getting all the information from the safety data sheets (second step), starts calculating the scores of every single section according to the instructions supplied in the check –list. The third step considers the effective duration of the job. The value shown below: time (hour) <1 = 0.125 time (hour) 1-4 = 0.500 time (hour) 4-6 = 0.750 time (hour) >6 = 1.000 represents the element “ exposure time” and corresponds to the time percentage referred to a work-shift (8 hours). The results of evaluation of each of the three phases are significant factors and correspond to as many values of a formula which permits evaluation of dermal contamination hazards concerning the job:
where: SC(h) = skin contamination hazard SC(2) = skin contamination risk C(h) = chemical hazard characteristics t(exp) = exposure time
Conclusions
The check-list is proposed as a simplified method that can be employed in preliminary evaluation of occupational dermal contamination hazard due to exposure to chemicals exposure. The results of the assessment, expressed in hazard bands, allow the identification and the semi-quantitative definition of a frequently underestimated risk. The check-list is not meant as a substitute for the methods provided by Industrial Hygiene to evaluate occupational skin contamination, but as an additional easy instrument to identify the factors responsible for it in the workplace. Thanks to this preliminary analysis, the use of hygienic-industrial methods (method of skin substitutes, removal method, methods with fluorescent tracers) becomes more accurate and effective. The structure of the method, based on the standardized observation of exposure, enables the observer to classify in order of importance the factors responsible for contamination risk (working conditions, use of protective devices, worker, workplace, and observed contamination) on which carry out improvements and verify their effectiveness. Also the characteristics of the chemicals in use are carefully evaluated and their replacement can be suggested under certain circumstances. The check-list presents some inevitable simplifications: since the weight of each determinant is unknown, uncertain or controversial, the values given to the items are mainly founded on experience; however such simplification permits a reasoned approach to the problem and its careful evaluation. For this reason the observer has a difficult demanding task: consequently the professional figure of the observer is to be identified in a medical expert or in a well-trained person (a prevention specialist, etc.). A further limit is the time needed to fill in the check-list (15-20 minutes) and to trainer the observer. This check-list, which is being applied to an extended number of jobs, will certainly improve some of the imprecise aspects of the methods in use; at the same time, dermal exposure is quantified using different sampling strategies in order to test the check-list reliability. It is therefore a practical useful method to be employed both to evaluate dermal exposure and to correct the factors responsible for contamination risk and, finally, verify the effectiveness of the interventions carried out. The check-list represents a first approach which should be followed, with the help of the results of Industrial Hygiene methods, by chemical absorption evaluation made through the application of predictable models knowing both the extent of skin contamination and flow of the chemical through the skin.
Content last modified: 15 May 2005 |
