INDUSTRIAL HYGIENE The 3 definite elements in industrial hygiene are the recognition, evaluation and control of occupational health hazards. The recognition of health hazards hasprimacy, since it must take place before proper evaluation or (if needed) control can takeplace. Upon recognition of a health hazard, theindustrial hygienist should be able to identify measures necessary for proper evaluation.
Upon completion of the evaluation, the industrialhygienist then is in a position – in consultation with other members of the occupational health safetyteam – to recommend controls needed to reduce exposures to tolerable limits. -1). Recognition of health hazards in the workplace This is the first step in the process leading to evaluation and control and entails the identification of materials and processesthat have the potential for causing harm to workers.
Sources of information about health hazards include clinical data about health problems in exposedpopulations; information in scientific journals and reports of governmentagencies; direct reports from workers,union representatives, supervisors, or employers.
Inspection of the workplace is the best source of directly relevant data about health hazards. There is no substitute for observation of work practices, use of chemical andphysical agents, and apparent effectiveness of control measures. The physician should be able to recognize major and obvious health hazards and distinguish those that require formal evaluation by the industrial hygienist.
The “walk through survey” in the company of the occupational health physician is the first and most important technique for recognition of occupational health hazards. The survey should begin with a proper introduction to plant management anddiscussion of the purpose of the survey and inquiry about any relevant recent complains.
Following the process flow through the plant is most productive. The survey might thus begin at the loading dock, where materialsentering the plant can be examined. Warning labels, descriptive language about the chemical composition of materials, and the packing of the incoming materials should be noted.
Questions should then be asked regarding the handling of unknown materials or materials about whichinsufficient information is available. The incoming materials should then be followed into the process flow stream, and each of the process of interest in the plant should be observed in action.
Of interest throughout the survey will be the methods used formaterial handling, particularly at the places where they aretransferred from manufacturers’ containers into vessels for use within the plant.
Observations to be made. At each point in the process, the industrial hygienist should observe handling procedures as well as any protective measures that are employed. Use ofrespiratory protection and protective clothingshould be recorded, as well as other common sense observations such as the apparent effectiveness of engineering controls – as indicated by absence of characteristicodors, visible dust accumulations, and loud noise.
The survey should continue throughto the final product produced by the plant and its packing. The industrial hygienist should also follow the pathway of any wastematerials and determine their disposal sites.
The number of employees at each stepshould be noted, as well as any relevant data on gender, ethnicity, or age that might affect employees’ sensitivity to chemicals in the workplace. It is also important to look for obviousstigmas such as drying of skin, as might expected where exposure to solvents occurs.
Data review.Important part of the industrial hygienist’srole in recognition of health hazards in the workplace will be data review. Such data may include reports fromphysicians on clinical findings that maybe related to exposures in the workplace as well as a review of company records on materials coming into the workplace that may present significant hazards.
A common-sense duty of the employer is to inform workers of the nature andhazards of materials to which they may be exposed. In some cases, the industrial hygienist mustassess the potential for harm of chemicals for which no reliable human toxicological data are available. This need arises most often in research and development settings but also wherever chemical intermediates are produced.
An important consideration is that the worker must be protected at all cost. If uncertaintyexists, it should be resolved in favor of highest standard of concern. Upon competition of the walk-through survey, the industrial hygienist will ordinary have aclosing conference with the plant management, at which time obvious concerns can be discussed and follow-up measures agreed upon.
2).Evaluation of health hazardsEvaluation of health hazards withinthe plant will include measurements of exposures, comparison of thoseexposures to existing standards, and recommendations of controls, if needed.
Exposure measurements.They are intended to be determinationsof doses delivered to the individual.The mere existence of chemicals in the workplace – or even in the workplaceatmosphere – does not necessary imply that the chemicals are being delivered to a sensitive organ system.
The effective dose will depend upon suchthings as particle sizes of dusts in the air,the use of protective devices (respirators, protective clothing), and the existence of other contaminants in the workplace.The task of determining the dose delivered to the worker may be complicated by the existence of multiple pathways of absorption and metabolism.
Such contaminants as lead are absorbed readily both through inhalation and ingestion, and both routes of intake mustbe considered in evaluation of the potential for harm. Similarly, many solvents are readily absorbed through the skin, and mere determination of airborne levels is not sufficient to determine the complete range of potential exposures.
Inhalation of airborne contaminants is the major route of entry for systemicintoxicants. Thus, evaluation and control of airborne contaminants is an important part of any occupational health program. Sampling and analysis of airbornecontaminants is the definite function of the industrial hygienist. The methods for sampling and analysis of airborne contaminants have been already discussed.
Evaluation of physical agentsrequires specialized equipment that is often not routinely available (except for sound level meters). Evaluation of ionizing or non- ionizing radiation requires specialized training.
3).Control of health hazardsUpon completion of evaluation, the industrial hygienist should recommend appropriate controls, if needed. Recommendations should take into account not only the conditions found during thesurvey but also those that may be expected to prevail in the future. Controls should be adequate to prevent unnecessary exposureduring accidents and emergencies as well as during normal conditions.
Engineering controls Engineering controls to toxic exposures consist mainly of: - enclosure – building structures around the sources of emissions- isolation – placing hazardous process components in areas with limited human contact and - VENTILATION
Local exhaust ventilation confirms to the principle that control should be implementedas near to the source as practically possible.Thus, application of a local exhaust inlet on a specific tool (such as grinder) would bemore desirable than performing the grindingoperation in a ventilated hood, which in turn would be more desirable than installing general ventilation in the room where the grinding is performed.
In a situation where a very toxic substanceis being manipulated in such a way that the exposure is possible, all 3 ventilation systems might be reasonable to use. Thus, the operator would be protected by the ventilation of the specific tool, nearbyworkers (as well as the operator) would be protected by the hood and the reminder of the building would be protected by the general ventilation system.
Design of ventilation systems forcontamination control should ordinarily not to be left to engineers without specific background or experience.Similarly, an industrial hygienist without engineering training and experience inthe process to be controlled may produce an unsatisfactory design.
Substitution All possibilities for substitution of a nontoxic for a toxic material or agent should be explored. If a toxic material can be dispersed with a less harmful, that should be done.Substitution can be done, of course, if a useful substitute is available – one that is suitablefor existing processes or for which the process can be relatively easily adapted.
Controls on human behavior – these can be subdivided into the general categories of administrative c ontrols and work practice controls. - Administrative controls – includes such things as establishment of prohibited areas, areas where smoking and eating are either prohibited or allowed, and safe pathways through the work environment.
Administrative controls will also include work scheduling in such a way that dangerous operations are carried out when fewest workers are present. Less desirable is the practice of scheduling individual workers toperform tasks for short periods, where excessive exposures would be incurred.
This practice was at one time common innuclear power industry, where temporary employees (“jumpers”) were employedand paid by the day, although their actualwork period may have been as short as 15minutes. Such practices, where exposure to carcinogenic or genotoxic agent is spread across a larger population groupalthough individual exposures are lower, is entirely unacceptable.
- Work practices control – implies control over the behavior of individual workers on the job.Such details as handling of contaminated tools are included.Education (on the hazards to be avoided) and training (on the desired practices) are required.
Controls on work practices are particularly important whereengineering controls are either notadequate or not possible and where there is significant potential for generation of airbornecontaminants outside of controlled places.
Personal protection Personal protective equipment use,though often essential, is less desirable than other approaches because of the difficulty in ensuring that it is both used and effective. Examples on construction sites are “hard hats” and “safety shoes”.
In laboratory environments, the use of protective eyewear is common,as is the use of protective garments, such as laboratory coats. However, there are significant complexities in both design and function of the protective devices used to reduce exposures.
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