When sampling to obtain a picture of the behaviour of contaminants, from the source throughout the work environment, accuracy and precision are not as critical as they would be for exposure assessment. This method combines a video image of the worker with a scale showing airborne contaminant concentrations, which are continuously measured, at the breathing zone, with a real-time monitoring instrument, thus making it possible to visualize how the concentration varies while the task is performed.
This provides an excellent tool for comparing the relative efficacy of different control measures, such as ventilation and work practices, thus contributing to better design. Measurements are also needed to assess the efficiency of control measures. The primary goal of occupational hygiene is the implementation of appropriate hazard prevention and control measures in the work environment.
The absence of legally established standards should not be an obstacle to the implementation of the necessary measures to prevent harmful exposures or control them to the lowest level feasible. When serious hazards are obvious, control should be recommended, even before quantitative evaluations are carried out. Some examples of hazards in obvious need of action without the necessity of prior environmental sampling are electroplating carried out in an unventilated, small room, or using a jackhammer or sand-blasting equipment with no environmental controls or protective equipment.
An Overview on Industrial Hygiene Hazards and Controls | | ISHN
For such recognized health hazards, the immediate need is control, not quantitative evaluation. There are three major groups of control measures: engineering controls, work practices and personal measures. The most efficient hazard prevention approach is the application of engineering control measures which prevent occupational exposures by managing the work environment, thus decreasing the need for initiatives on the part of workers or potentially exposed persons. Engineering measures usually require some process modifications or mechanical structures, and involve technical measures that eliminate or reduce the use, generation or release of hazardous agents at their source, or, when source elimination is not possible, engineering measures should be designed to prevent or reduce the spread of hazardous agents into the work environment by:.
Control interventions which involve some modification of the source are the best approach because the harmful agent can be eliminated or reduced in concentration or intensity. When source modifications are not feasible, or are not sufficient to attain the desired level of control, then the release and dissemination of hazardous agents in the work environment should be prevented by interrupting their transmission path through measures such as isolation e. Other measures aiming at reducing exposures in the work environment include adequate workplace design, dilution or displacement ventilation, good housekeeping and adequate storage.
Labelling and warning signs can assist workers in safe work practices. Monitoring and alarm systems may be required in a control programme. Monitors for carbon monoxide around furnaces, for hydrogen sulphide in sewage work, and for oxygen deficiency in closed spaces are some examples. The position of the worker may affect the conditions of exposure e. It should be pointed out that all other possibilities of control should be explored before considering the use of personal protective equipment, as this is the least satisfactory means for routine control of exposures, particularly to airborne contaminants.
Other personal preventive measures include education and training, personal hygiene and limitation of exposure time. Continuous evaluations, through environmental monitoring and health surveillance, should be part of any hazard prevention and control strategy. Appropriate control technology for the work environment must also encompass measures for the prevention of environmental pollution air, water, soil , including adequate management of hazardous waste.
Although most of the control principles hereby mentioned apply to airborne contaminants, many are also applicable to other types of hazards. For example, a process can be modified to produce less air contaminants or to produce less noise or less heat. An isolating barrier can isolate workers from a source of noise, heat or radiation. Far too often prevention dwells on the most widely known measures, such as local exhaust ventilation and personal protective equipment, without proper consideration of other valuable control options, such as alternative cleaner technologies, substitution of materials, modification of processes, and good work practices.
It often happens that work processes are regarded as unchangeable when, in reality, changes can be made which effectively prevent or at least reduce the associated hazards. Hazard prevention and control in the work environment requires knowledge and ingenuity. Effective control does not necessarily require very costly and complicated measures. In many cases, hazard control can be achieved through appropriate technology, which can be as simple as a piece of impervious material between the naked shoulder of a dock worker and a bag of toxic material that can be absorbed through the skin.
It can also consist of simple improvements such as placing a movable barrier between an ultraviolet source and a worker, or training workers in safe work practices. Aspects to be considered when selecting appropriate control strategies and technology, include the type of hazardous agent nature, physical state, health effects, routes of entry into the body , type of source s , magnitude and conditions of exposure, characteristics of the workplace and relative location of workstations.
The required skills and resources for the correct design, implementation, operation, evaluation and maintenance of control systems must be ensured. Systems such as local exhaust ventilation must be evaluated after installation and routinely checked thereafter. Only regular monitoring and maintenance can ensure continued efficiency, since even well-designed systems may lose their initial performance if neglected. Control measures should be integrated into hazard prevention and control programmes, with clear objectives and efficient management, involving multidisciplinary teams made up of occupational hygienists and other occupational health and safety staff, production engineers, management and workers.
Programmes must also include aspects such as hazard communication, education and training covering safe work practices and emergency procedures. Health promotion aspects should also be included, since the workplace is an ideal setting for promoting healthy life-styles in general and for alerting as to the dangers of hazardous non-occupational exposures caused, for example, by shooting without adequate protection, or smoking. Risk assessment is a methodology that aims at characterizing the types of health effects expected as a result of a certain exposure to a given agent, as well as providing estimates on the probability of occurrence of these health effects, at different levels of exposure.
It is also used to characterize specific risk situations. It involves hazard identification, the establishment of exposure-effect relationships, and exposure assessment, leading to risk characterization. The second step establishes how much exposure causes how much of a given effect in how many of the exposed persons. This knowledge is essential for the interpretation of exposure assessment data. Exposure assessment is part of risk assessment, both when obtaining data to characterize a risk situation and when obtaining data for the establishment of exposure-effect relationships from epidemiological studies.
In the latter case, the exposure that led to a certain occupational or environmentally caused effect has to be accurately characterized to ensure the validity of the correlation. Risk assessment is a dynamic process, as new knowledge often discloses harmful effects of substances until then considered relatively harmless; therefore the occupational hygienist must have, at all times, access to up-to-date toxicological information.
Spectroscopic Techniques in Industrial Hygiene
Another implication is that exposures should always be controlled to the lowest feasible level. Figure Risk management in the work environment It is not always feasible to eliminate all agents that pose occupational health risks because some are inherent to work processes that are indispensable or desirable; however, risks can and must be managed. Risk assessment provides a basis for risk management. However, while risk assessment is a scientific procedure, risk management is more pragmatic, involving decisions and actions that aim at preventing, or reducing to acceptable levels, the occurrence of agents which may pose hazards to the health of workers, surrounding communities and the environment, also accounting for the socio-economic and public health context.
Risk management takes place at different levels; decisions and actions taken at the national level pave the way for the practice of risk management at the workplace level. Traditionally, the profession responsible for most of these decisions and actions in the workplace is occupational hygiene. One key decision in risk management, that of acceptable risk what effect can be accepted, in what percentage of the working population, if any at all?
This leads to the establishment of targets for control, usually at the workplace level by the occupational hygienist, who should have knowledge of the legal requirements. All these decisions and actions must be integrated into a realistic plan, which requires multidisciplinary and multisectorial coordination and collaboration. Although risk management involves pragmatic approaches, its efficiency should be scientifically evaluated. Unfortunately risk management actions are, in most cases, a compromise between what should be done to avoid any risk and the best which can be done in practice, in view of financial and other limitations.
Risk management concerning the work environment and the general environment should be well coordinated; not only are there overlapping areas, but, in most situations, the success of one is interlinked with the success of the other. Political will and decision making at the national level will, directly or indirectly, influence the establishment of occupational hygiene programmes or services, either at the governmental or private level.
It is beyond the scope of this article to provide detailed models for all types of occupational hygiene programmes and services; however, there are general principles that are applicable to many situations and may contribute to their efficient implementation and operation. A comprehensive occupational hygiene service should have the capability to carry out adequate preliminary surveys, sampling, measurements and analysis for hazard evaluation and for control purposes, and to recommend control measures, if not to design them. Key elements of a comprehensive occupational hygiene programme or service are human and financial resources, facilities, equipment and information systems, well organized and coordinated through careful planning, under efficient management, and also involving quality assurance and continuous programme evaluation.
Successful occupational hygiene programmes require a policy basis and commitment from top management. The procurement of financial resources is beyond the scope of this article. Adequate human resources constitute the main asset of any programme and should be ensured as a priority. All staff should have clear job descriptions and responsibilities. If needed, provisions for training and education should be made. The basic requirements for occupational hygiene programmes include:.
One important aspect is professional competence, which must not only be achieved but also maintained. Continuous education, in or outside the programme or service, should cover, for example, legislation updates, new advances and techniques, and gaps in knowledge. Participation in conferences, symposia and workshops also contribute to the maintenance of competence. Health and safety should be ensured for all staff in field surveys, laboratories and offices. Occupational hygienists may be exposed to serious hazards and should wear the required personal protective equipment.
Depending on the type of work, immunization may be required. If rural work is involved, depending on the region, provisions such as antidote for snake bites should be made. Laboratory safety is a specialized field discussed elsewhere in this Encyclopaedia. Ergonomic and psychosocial factors should also be considered. These include offices and meeting room s , laboratories and equipment, information systems and library. Facilities should be well designed, accounting for future needs, as later moves and adaptations are usually more costly and time consuming.
Occupational hygiene laboratories should have in principle the capability to carry out qualitative and quantitative assessment of exposure to airborne contaminants chemicals and dusts , physical agents noise, heat stress, radiation, illumination and biological agents. In the case of most biological agents, qualitative assessments are enough to recommend controls, thus eliminating the need for the usually difficult quantitative evaluations.
Although some direct-reading instruments for airborne contaminants may have limitations for exposure assessment purposes, these are extremely useful for the recognition of hazards and identification of their sources, the determination of peaks in concentration, the gathering of data for control measures, and for checking on controls such as ventilation systems. In connection with the latter, instruments to check air velocity and static pressure are also needed. These aspects include portability, required source of energy, calibration and maintenance requirements, and availability of the required expendable supplies.
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Calibration of all types of occupational hygiene measuring and sampling as well as analytical equipment should be an integral part of any procedure, and the required equipment should be available. Maintenance and repairs are essential to prevent equipment from staying idle for long periods of time, and should be ensured by manufacturers, either by direct assistance or by providing training of staff. If a completely new programme is being developed, only basic equipment should be initially purchased, more items being added as the needs are established and operational capabilities ensured.
However, even before equipment and laboratories are available and operational, much can be achieved by inspecting workplaces to qualitatively assess health hazards, and by recommending control measures for recognized hazards. Lack of capability to carry out quantitative exposure assessments should never justify inaction concerning obviously hazardous exposures.
This is particularly true for situations where workplace hazards are uncontrolled and heavy exposures are common. This includes library books, periodicals and other publications , databases e. Such systems should include e-mail, which opens new horizons for communications and discussions, either individually or as groups, thus facilitating and promoting exchange of information throughout the world. Timely and careful planning for the implementation, management and periodic evaluation of a programme is essential to ensure that the objectives and goals are achieved, while making the best use of the available resources.
Operational costs should not be underestimated, since lack of resources may seriously hinder the continuity of a programme. Requirements which cannot be overlooked include:. Resources must be optimized through careful study of all elements which should be considered as integral parts of a comprehensive service.
A well-balanced allocation of resources to the different units field measurements, sampling, analytical laboratories, etc.
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Moreover, allocation of resources should allow for flexibility, because occupational hygiene services may have to undergo adaptations in order to respond to the real needs, which should be periodically assessed. Communication, sharing and collaboration are key words for successful teamwork and enhanced individual capabilities. There should be close interaction with other occupational health professionals, particularly occupational physicians and nurses, ergonomists and work psychologists, as well as safety professionals. At the workplace level, this should include workers, production personnel and managers.
The implementation of successful programmes is a gradual process. Therefore, at the planning stage, a realistic timetable should be prepared, according to well-established priorities and in view of the available resources. Management involves decision-making as to the goals to be achieved and actions required to efficiently achieve these goals, with participation of all concerned, as well as foreseeing and avoiding, or recognizing and solving, the problems which may create obstacles to the completion of the required tasks. It should be kept in mind that scientific knowledge is no assurance of the managerial competence required to run an efficient programme.
The importance of implementing and enforcing correct procedures and quality assurance cannot be overemphasized, since there is much difference between work done and work well done. Good management should be able to distinguish between what is impressive and what is important; very detailed surveys involving sampling and analysis, yielding very accurate and precise results, may be very impressive, but what is really important are the decisions and actions that will be taken afterwards.
The concept of quality assurance, involving quality control and proficiency testing, refers primarily to activities which involve measurements. Although these concepts have been more often considered in connection with analytical laboratories, their scope has to be extended to also encompass sampling and measurements. Whenever sampling and analysis are required, the complete procedure should be considered as one, from the point of view of quality. Since no chain is stronger than the weakest link, it is a waste of resources to use, for the different steps of a same evaluation procedure, instruments and techniques of unequal levels of quality.
The accuracy and precision of a very good analytical balance cannot compensate for a pump sampling at a wrong flowrate. The performance of laboratories has to be checked so that the sources of errors can be identified and corrected. There is need for a systematic approach in order to keep the numerous details involved under control.
Concerning sampling, or measurements with direct-reading instruments including for measurement of physical agents , quality involves adequate and correct:. Furthermore, it is essential to have a correct treatment of the obtained data and interpretation of results, as well as accurate reporting and record keeping. It should cover both the sampling and the analytical procedures. The concept of quality must be applied to all steps of occupational hygiene practice, from the recognition of hazards to the implementation of hazard prevention and control programmes.
With this in mind, occupational hygiene programmes and services must be periodically and critically evaluated, aiming at continuous improvement. Its practice involves many steps, which are interlinked and which have no meaning by themselves but must be integrated into a comprehensive approach. A workplace hazard can be defined as any condition that may adversely affect the well-being or health of exposed persons.
Recognition of hazards in any occupational activity involves characterization of the workplace by identifying hazardous agents and groups of workers potentially exposed to these hazards. The hazards might be of chemical, biological or physical origin see table Some agents like metals e. A toxic agent may not constitute a hazard at low concentrations or if no one is exposed. Basic to the recognition of hazards are identification of possible agents at the workplace, knowledge about health risks of these agents and awareness of possible exposure situations.
Chemicals enter the body principally through inhalation, skin absorption or ingestion. The toxic effect might be acute, chronic or both. Corrosive chemicals actually cause tissue destruction at the site of contact. Skin, eyes and digestive system are the most commonly affected parts of the body. Irritants cause inflammation of tissues where they are deposited. Skin irritants may cause reactions like eczema or dermatitis. Severe respiratory irritants might cause shortness of breath, inflammatory responses and oedema.
Respiratory: aldehydes, alkaline dusts, ammonia, nitrogendioxide, phosgene, chlorine, bromine, ozone. Chemical allergens or sensitizers can cause skin or respiratory allergic reactions. Skin: colophony rosin , formaldehyde, metals like chromium or nickel, some organic dyes, epoxy hardeners, turpentine.
Asphyxiants exert their effects by interfering with the oxygenation of the tissues. Simple asphyxiants are inert gases that dilute the available atmospheric oxygen below the level required to support life. Oxygen-deficient atmospheres may occur in tanks, holds of ships, silos or mines. Oxygen concentration in air should never be below Chemical asphyxiants prevent oxygen transport and the normal oxygenation of blood or prevent normal oxygenation of tissues.
Known human carcinogens are chemicals that have been clearly demonstrated to cause cancer in humans. Probable human carcinogens are chemicals that have been clearly demonstrated to cause cancer in animals or the evidence is not definite in humans. Soot and coal tars were the first chemicals suspected to cause cancer. Known: benzene leukaemia ; vinyl chloride liver angio-sarcoma ; 2-naphthylamine, benzidine bladder cancer ; asbestos lung cancer, mesothelioma ; hardwood dust nasalor nasal sinus adenocarcinoma. Reproductive toxicants interfere with reproductive or sexual functioning of an individual.
Manganese, carbon disulphide, monomethyl and ethyl ethers of ethylene glycol, mercury. Developmental toxicants are agents that may cause an adverse effect in offspring of exposed persons; for example, birth defects. Embryotoxic or foetotoxic chemicals can cause spontaneous abortions or miscarriages. Systemic poisons are agents that cause injury to particular organs or body systems. Biological hazards can be defined as organic dusts originating from different sources of biological origin such as virus, bacteria, fungi, proteins from animals or substances from plants such as degradation products of natural fibres.
The aetiological agent might be derived from a viable organism or from contaminants or constitute a specific component in the dust. Biological hazards are grouped into infectious and non-infectious agents. Non-infectious hazards can be further divided into viable organisms, biogenic toxins and biogenic allergens. Occupational diseases from infectious agents are relatively uncommon. Workers at risk include employees at hospitals, laboratory workers, farmers, slaughterhouse workers, veterinarians, zoo keepers and cooks.
Susceptibility is very variable e. Hepatitis B, tuberculosis, anthrax, brucella, tetanus, chlamydia psittaci, salmonella. Viable organisms include fungi, spores and mycotoxins; biogenic toxins include endotoxins, aflatoxin and bacteria. The products of bacterial and fungal metabolism are complex and numerous and affected by temperature, humidity and kind of substrate on which they grow. Chemically they might consist of proteins, lipoproteins or mucopolysaccharides. Examples are Gram positive and Gram negative bacteria and moulds.
Workers at risk include cotton mill workers, hemp and flax workers, sewage and sludge treatment workers, grain silo workers. Biogenic allergens include fungi, animal-derived proteins, terpenes, storage mites and enzymes. A considerable part of the biogenic allergens in agriculture comes from proteins from animal skin, hair from furs and protein from the faecal material and urine.
Allergens might be found in many industrial environments, such as fermentation processes, drug production, bakeries, paper production, wood processing saw mills, production, manufacturing as well as in bio-technology enzyme and vaccine production, tissue culture and spice production. In sensitized persons, exposure to the allergic agents may induce allergic symptoms such as allergic rhinitis, conjunctivitis or asthma. Allergic alveolitis is characterized by acute respiratory symptoms like cough, chills, fever, headache and pain in the muscles, which might lead to chronic lung fibrosis.
Occupational asthma: wool, furs, wheat grain, flour, red cedar, garlic powder. Noise is considered as any unwanted sound that may adversely affect the health and well-being of individuals or populations. Aspects of noise hazards include total energy of the sound, frequency distribution, duration of exposure and impulsive noise.
Hearing acuity is generally affected first with a loss or dip at Hz followed by losses in the frequency range from to Hz. Noise might result in acute effects like communication problems, decreased concentration, sleepiness and as a consequence interference with job performance. Exposure to high levels of noise usually above 85 dBA or impulsive noise about dBC over a significant period of time may cause both temporary and chronic hearing loss.
Permanent hearing loss is the most common occupational disease in compensation claims. Method of operation and skilfulness of the operator seem to play an important role in the development of harmful effects of vibration. Vibrating tools may also affect the peripheral nervous system and the musculo-skeletal system with reduced grip strength, low back pain and degenerative back disorders. The most important chronic effect of ionizing radiation is cancer, including leukaemia.
Overexposure from comparatively low levels of radiation have been associated with dermatitis of the hand and effects on the haematological system. Processes or activities which might give excessive exposure to ionizing radiation are very restricted and regulated. Nuclear reactors, medical and dental x-ray tubes, particle accelerators, radioisotopes.
Non-ionizing radiation consists of ultraviolet radiation, visible radiation, infrared, lasers, electromagnetic fields microwaves and radio frequency and extreme low frequency radiation. IR radiation might cause cataracts. High-powered lasers may cause eye and skin damage. There is an increasing concern about exposure to low levels of electromagnetic fields as a cause of cancer and as a potential cause of adverse reproductive outcomes among women, especially from exposure to video display units.
The question about a causal link to cancer is not yet answered. Recent reviews of available scientific knowledge generally conclude that there is no association between use of VDUs and adverse reproductive outcome. Ultraviolet radiation: arc welding and cutting; UV curing of inks, glues, paints, etc. Before any occupational hygiene investigation is performed the purpose must be clearly defined. The purpose of an occupational hygiene investigation might be to identify possible hazards, to evaluate existing risks at the workplace, to prove compliance with regulatory requirements, to evaluate control measures or to assess exposure with regard to an epidemiological survey.
This article is restricted to programmes aimed at identification and classification of hazards at the workplace. Many models or techniques have been developed to identify and evaluate hazards in the working environment. They differ in complexity, from simple checklists, preliminary industrial hygiene surveys, job-exposure matrices and hazard and operability studies to job exposure profiles and work surveillance programmes Renes ; Gressel and Gideon ; Holzner, Hirsh and Perper ; Goldberg et al.
No single technique is a clear choice for everyone, but all techniques have parts which are useful in any investigation. The usefulness of the models also depends on the purpose of the investigation, size of workplace, type of production and activity as well as complexity of operations. Identification and classification of hazards can be divided into three basic elements: workplace characterization, exposure pattern and hazard evaluation. A workplace might have from a few employees up to several thousands and have different activities e. At a workplace different activities can be localized to special areas such as departments or sections.
In an industrial process, different stages and operations can be identified as production is followed from raw materials to finished products. Detailed information should be obtained about processes, operations or other activities of interest, to identify agents utilized, including raw materials, materials handled or added in the process, primary products, intermediates, final products, reaction products and by-products.
Additives and catalysts in a process might also be of interest to identify. Raw material or added material which has been identified only by trade name must be evaluated by chemical composition. Information or safety data sheets should be available from manufacturer or supplier. Some stages in a process might take place in a closed system without anyone exposed, except during maintenance work or process failure. These events should be recognized and precautions taken to prevent exposure to hazardous agents.
Other processes take place in open systems, which are provided with or without local exhaust ventilation. A general description of the ventilation system should be provided, including local exhaust system. When possible, hazards should be identified in the planning or design of new plants or processes, when changes can be made at an early stage and hazards might be anticipated and avoided.
Conditions and procedures that may deviate from the intended design must be identified and evaluated in the process state. Recognition of hazards should also include emissions to the external environment and waste materials. Facility locations, operations, emission sources and agents should be grouped together in a systematic way to form recognizable units in the further analysis of potential exposure. In each unit, operations and agents should be grouped according to health effects of the agents and estimation of emitted amounts to the work environment.
The main exposure routes for chemical and biological agents are inhalation and dermal uptake or incidentally by ingestion. The exposure pattern depends on frequency of contact with the hazards, intensity of exposure and time of exposure. Working tasks have to be systematically examined. It is important not only to study work manuals but to look at what actually happens at the workplace. Workers might be directly exposed as a result of actually performing tasks, or be indirectly exposed because they are located in the same general area or location as the source of exposure.
It might be necessary to start by focusing on working tasks with high potential to cause harm even if the exposure is of short duration. Non-routine and intermittent operations e. Working tasks and situations might also vary throughout the year. Within the same job title exposure or uptake might differ because some workers wear protective equipment and others do not. In large plants, recognition of hazards or a qualitative hazard evaluation very seldom can be performed for every single worker.
Therefore workers with similar working tasks have to be classified in the same exposure group. Differences in working tasks, work techniques and work time will result in considerably different exposure and have to be considered. Persons working outdoors and those working without local exhaust ventilation have been shown to have a larger day-to-day variability than groups working indoors with local exhaust ventilation Kromhout, Symanski and Rappaport Within the groups, workers potentially exposed must be identified and classified according to hazardous agents, routes of exposure, health effects of the agents, frequency of contact with the hazards, intensity and time of exposure.
Different exposure groups should be ranked according to hazardous agents and estimated exposure in order to determine workers at greatest risk. Possible health effects of chemical, biological and physical agents present at the workplace should be based on an evaluation of available epidemiological, toxicological, clinical and environmental research. Up-to-date information about health hazards for products or agents used at the workplace should be obtained from health and safety journals, databases on toxicity and health effects, and relevant scientific and technical literature.
They also contain information about health hazards, protective equipment, preventive actions, manufacturer or supplier, and so on. Sometimes the ingredients reported are rather rudimentary and have to be supplemented with more detailed information. Monitored data and records of measurements should be studied. Agents with TLVs provide general guidance in deciding whether the situation is acceptable or not, although there must be allowance for possible interactions when workers are exposed to several chemicals.
Within and between different exposure groups, workers should be ranked according to health effects of agents present and estimated exposure e. Those with the highest ranks deserve highest priority.
Before any prevention activities start it might be necessary to perform an exposure monitoring programme. All results should be documented and easily attainable. A working scheme is illustrated in figure In occupational hygiene investigations the hazards to the outdoor environment e. Hazards might be of chemical, biological or physical origin. In this section and in table More detailed information will be found elsewhere in this Encyclopaedia. Chemicals can be grouped into gases, vapours, liquids and aerosols dusts, fumes, mists.
Gases are substances that can be changed to liquid or solid state only by the combined effects of increased pressure and decreased temperature. Handling gases always implies risk of exposure unless they are processed in closed systems. Gases in containers or distribution pipes might accidentally leak. In processes with high temperatures e. Vapours are the gaseous form of substances that normally are in the liquid or solid state at room temperature and normal pressure. When a liquid evaporates it changes to a gas and mixes with the surrounding air.
A vapour can be regarded as a gas, where the maximal concentration of a vapour depends on the temperature and the saturation pressure of the substance. Any process involving combustion will generate vapours or gases.
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Degreasing operations might be performed by vapour phase degreasing or soak cleaning with solvents. Work activities like charging and mixing liquids, painting, spraying, cleaning and dry cleaning might generate harmful vapours. Liquids may consist of a pure substance or a solution of two or more substances e. A liquid stored in an open container will partially evaporate into the gas phase. The concentration in the vapour phase at equilibrium depends on the vapour pressure of the substance, its concentration in the liquid phase, and the temperature.
Operations or activities with liquids might give rise to splashes or other skin contact, besides harmful vapours. Dusts consist of inorganic and organic particles, which can be classified as inhalable, thoracic or respirable, depending on particle size. Most organic dusts have a biological origin. Inorganic dusts will be generated in mechanical processes like grinding, sawing, cutting, crushing, screening or sieving. Dusts may be dispersed when dusty material is handled or whirled up by air movements from traffic. Handling dry materials or powder by weighing, filling, charging, transporting and packing will generate dust, as will activities like insulation and cleaning work.
Fumes are solid particles vaporized at high temperature and condensed to small particles. The vaporization is often accompanied by a chemical reaction such as oxidation. The single particles that make up a fume are extremely fine, usually less than 0. Examples are fumes from welding, plasma cutting and similar operations. Mists are suspended liquid droplets generated by condensation from the gaseous state to the liquid state or by breaking up a liquid into a dispersed state by splashing, foaming or atomizing.
Examples are oil mists from cutting and grinding operations, acid mists from electroplating, acid or alkali mists from pickling operations or paint spray mists from spraying operations. Occupational surveillance involves active programmes to anticipate, observe, measure, evaluate and control exposures to potential health hazards in the workplace. Surveillance often involves a team of people that includes an occupational hygienist, occupational physician, occupational health nurse, safety officer, toxicologist and engineer.
Depending upon the occupational environment and problem, three surveillance methods can be employed: medical, environmental and biological. Medical surveillance is used to detect the presence or absence of adverse health effects for an individual from occupational exposure to contaminants, by performing medical examinations and appropriate biological tests.
Environmental surveillance is used to document potential exposure to contaminants for a group of employees, by measuring the concentration of contaminants in the air, in bulk samples of materials, and on surfaces. Biological surveillance is used to document the absorption of contaminants into the body and correlate with environmental contaminant levels, by measuring the concentration of hazardous substances or their metabolites in the blood, urine or exhaled breath of workers.
Medical surveillance is performed because diseases can be caused or exacerbated by exposure to hazardous substances. It requires an active programme with professionals who are knowledgeable about occupational diseases, diagnoses and treatment. Medical surveillance programmes provide steps to protect, educate, monitor and, in some cases, compensate the employee. It can include pre-employment screening programmes, periodic medical examinations, specialized tests to detect early changes and impairment caused by hazardous substances, medical treatment and extensive record keeping.
Pre-employment screening involves the evaluation of occupational and medical history questionnaires and results of physical examinations. Questionnaires provide information concerning past illnesses and chronic diseases especially asthma, skin, lung and heart diseases and past occupational exposures. There are ethical and legal implications of pre-employment screening programmes if they are used to determine employment eligibility. However, they are fundamentally important when used to 1 provide a record of previous employment and associated exposures, 2 establish a baseline of health for an employee and 3 test for hypersusceptibility.
Medical examinations can include audiometric tests for hearing loss, vision tests, tests of organ function, evaluation of fitness for wearing respiratory protection equipment, and baseline urine and blood tests. Periodic medical examinations are essential for evaluating and detecting trends in the onset of adverse health effects and may include biological monitoring for specific contaminants and the use of other biomarkers.
Environmental and biological surveillance starts with an occupational hygiene survey of the work environment to identify potential hazards and contaminant sources, and determine the need for monitoring. For chemical agents, monitoring could involve air, bulk, surface and biological sampling. For physical agents, monitoring could include noise, temperature and radiation measurements.
If monitoring is indicated, the occupational hygienist must develop a sampling strategy that includes which employees, processes, equipment or areas to sample, the number of samples, how long to sample, how often to sample, and the sampling method. Industrial hygiene surveys vary in complexity and focus depending upon the purpose of the investigation, type and size of establishment, and nature of the problem.
There are no rigid formulas for performing surveys; however, thorough preparation prior to the on-site inspection significantly increases effectiveness and efficiency. Investigations that are motivated by employee complaints and illnesses have an additional focus of identifying the cause of the health problems. Indoor air quality surveys focus on indoor as well as outdoor sources of contamination.
Regardless of the occupational hazard, the overall approach to surveying and sampling workplaces is similar; therefore, this chapter will use chemical agents as a model for the methodology. The mere presence of occupational stresses in the workplace does not automatically imply that there is a significant potential for exposure; the agent must reach the worker.
The route of exposure can impact the type of monitoring performed as well as the hazard potential. For chemical and biological agents, workers are exposed through inhalation, skin contact, ingestion and injection; the most common routes of absorption in the occupational environment are through the respiratory tract and the skin.
To assess inhalation, the occupational hygienist observes the potential for chemicals to become airborne as gases, vapours, dusts, fumes or mists. Skin absorption of chemicals is important primarily when there is direct contact with the skin through splashing, spraying, wetting or immersion with fat-soluble hydrocarbons and other organic solvents. Immersion includes body contact with contaminated clothing, hand contact with contaminated gloves, and hand and arm contact with bulk liquids.
For some substances, such as amines and phenols, skin absorption can be as rapid as absorption through the lungs for substances that are inhaled. For some contaminants such as pesticides and benzidine dyes, skin absorption is the primary route of absorption, and inhalation is a secondary route. Such chemicals can readily enter the body through the skin, increase body burden and cause systemic damage. When allergic reactions or repeated washing dries and cracks the skin, there is a dramatic increase in the number and type of chemicals that can be absorbed into the body.
Ingestion, an uncommon route of absorption for gases and vapours, can be important for particulates, such as lead. Ingestion can occur from eating contaminated food, eating or smoking with contaminated hands, and coughing and then swallowing previously inhaled particulates. Injection of materials directly into the bloodstream can occur from hypodermic needles inadvertently puncturing the skin of health care workers in hospitals, and from high-velocity projectiles released from high-pressure sources and directly contacting the skin.
Airless paint sprayers and hydraulic systems have pressures high enough to puncture the skin and introduce substances directly into the body. The purpose of the initial survey, called the walk-through inspection, is to systematically gather information to judge whether a potentially hazardous situation exists and whether monitoring is indicated. An occupational hygienist begins the walk-through survey with an opening meeting that can include representatives of management, employees, supervisors, occupational health nurses and union representatives.
The occupational hygienist can powerfully impact the success of the survey and any subsequent monitoring initiatives by creating a team of people who communicate openly and honestly with one another and understand the goals and scope of the inspection.
Workers must be involved and informed from the beginning to ensure that cooperation, not fear, dominates the investigation. During the meeting, requests are made for process flow diagrams, plant layout drawings, past environmental inspection reports, production schedules, equipment maintenance schedules, documentation of personal protection programmes, and statistics concerning the number of employees, shifts and health complaints. All hazardous materials used and produced by an operation are identified and quantified.
A chemical inventory of products, by-products, intermediates and impurities is assembled and all associated Material Safety Data Sheets are obtained. Equipment maintenance schedules, age and condition are documented because the use of older equipment may result in higher exposures due to the lack of controls. After the meeting, the occupational hygienist performs a visual walk-through survey of the workplace, scrutinizing the operations and work practices, with the goal of identifying potential occupational stresses, ranking the potential for exposure, identifying the route of exposure and estimating the duration and frequency of exposure.
Examples of occupational stresses are given in figure The occupational hygienist uses the walk-through inspection to observe the workplace and have questions answered. Examples of observations and questions are given in figure In addition to the questions shown in figure Questions could address:. Non-routine tasks can result in significant peak exposures to chemicals that are difficult to predict and measure during a typical workday. Process changes and chemical substitutions may alter the release of substances into the air and affect subsequent exposure.
Changes in the physical layout of a work area can alter the effectiveness of an existing ventilation system. Changes in job functions can result in tasks performed by inexperienced workers and increased exposures. Renovations and repairs may introduce new materials and chemicals into the work environment which off-gas volatile organic chemicals or are irritants.
Indoor air quality surveys are distinct from traditional occupational hygiene surveys because they are typically encountered in non-industrial workplaces and may involve exposures to mixtures of trace quantities of chemicals, none of which alone appears capable of causing illness Ness The goal of indoor air quality surveys is similar to occupational hygiene surveys in terms of identifying sources of contamination and determining the need for monitoring.
However, indoor air quality surveys are always motivated by employee health complaints. In many cases, the employees have a variety of symptoms including headaches, throat irritation, lethargy, coughing, itching, nausea and non-specific hypersensitivity reactions that disappear when they go home.
When health complaints do not disappear after the employees leave work, non-occupational exposures should be considered as well. Non-occupational exposures include hobbies, other jobs, urban air pollution, passive smoking and indoor exposures in the home. Indoor air quality surveys frequently use questionnaires to document employee symptoms and complaints and link them to job location or job function within the building. The areas with the highest incidence of symptoms are then targeted for further inspection.
Sources of indoor air contaminants that have been documented in indoor air quality surveys include:. For indoor air quality investigations, the walk-through inspection is essentially a building and environmental inspection to determine potential sources of contamination both inside and outside of the building. Inside building sources include:. Observations and questions that can be asked during the survey are listed in figure Sampling and Measurement Strategies Occupational exposure limits After the walk-through inspection is completed, the occupational hygienist must determine whether sampling is necessary; sampling should be performed only if the purpose is clear.
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Manard, M. Schappert, E. Wylie and G. McMath, Anal. Search articles by author Benjamin T.