Contents
Introduction
Industrial hygiene has been defined as “that science and art devoted to the anticipation, recognition, evaluation, and control of those environmental factors or stresses arising in or from the workplace, which may cause sickness, impaired health and well-being, or significant discomfort among workers or among the citizens of the community.” Industrial hygienists use environmental monitoring and analytical methods to detect the extent of worker exposure and employ engineering, work practice controls, and other methods to control potential health hazards.
OSHA and Industrial Hygienists:
Under the OSH Act, OSHA develops and sets mandatory occupational safety and health requirements applicable to the more than 6 million workplaces in the U.S. OSHA relies on, among many others, industrial hygienists to evaluate jobs for potential health hazards. Developing and setting mandatory occupational safety and health standards involves determining the extent of employee exposure to hazards & deciding what is needed to control these hazards to protect workers. Industrial hygienists are trained to anticipate, recognize, evaluate, and recommend controls for environmental and physical hazards that can affect the health and well-being of workers.
More than 40 percent of the OSHA compliance officers who inspect America’s workplaces are industrial hygienists. Industrial hygienists also play a major role in developing and issuing OSHA standards to protect workers from health hazards associated with toxic chemicals, biological hazards, and harmful physical agents. They also provide technical assistance and support to the agency’s national and regional offices. OSHA also employs industrial hygienists who assist in setting up field enforcement procedures, and who issue technical interpretations of OSHA regulations and standards.
Industrial hygienists analyze, identify, and measure workplace hazards or stresses that can cause sickness, impaired health / significant discomfort in workers through chemical, physical, ergonomic, or biological exposures. Two roles of the OSHA industrial hygienist are to spot those conditions and help eliminate or control them through appropriate measures.
Work Site Analysis:
A work site analysis is an essential first step that helps an industrial hygienist determine what jobs and work stations are the sources of potential problems. During the work site analysis, the industrial hygienist measures and identifies exposures, problem tasks, and risks. The most-effective work site analyses include all jobs, operations, and work activities. The industrial hygienist inspects researches, or analyzes how the particular chemicals or physical hazards at that work site affect worker health. If a situation hazardous to health is discovered, the industrial hygienist recommends the appropriate corrective actions.
Recognizing and Controlling Hazards:
Industrial hygienists recognize that engineering, work practice, and administrative controls are the primary means of reducing employee exposure to occupational hazards.
Engineering controls minimize employee exposure by either reducing or removing the hazard at the source or isolating the worker from the hazard.
Engineering controls include eliminating toxic chemicals and substituting non-toxic chemicals, enclosing work processes or confining work operations, and the installation of general and local
Ventilation systems:
Work practice controls alter the manner in which a task is performed. Some fundamental and easily implemented work practice controls include
(1) changing existing work practices to follow proper procedures that minimize exposures while operating production and control equipment;
(2) inspecting and maintaining process and control equipment on a regular basis;
(3) implementing good housekeeping procedures;
(4) providing good supervision; and
(5) mandating that eating, drinking, smoking, chewing tobacco or gum, and applying cosmetics in regulated areas be prohibited. Administrative controls include controlling employees’ exposure by scheduling production and tasks, or both, in ways that minimize exposure levels. For example, the employer might schedule operations with the highest exposure potential during periods when the fewest employees are present.
When effective work practices or engineering controls are not feasible or while such controls are being instituted, appropriate personal protective equipment must be used. Examples of personal protective equipment are gloves, safety goggles, helmets, safety shoes, protective clothing, and respirators. To be effective, personal protective equipment must be individually selected, properly fitted and periodically refitted; conscientiously and properly worn; regularly maintained; and replaced, as necessary.
Examples of Job Hazards:
To be effective in recognizing and evaluating on-the-job hazards and recommending controls, industrial hygienists must be familiar with the hazards’ characteristics.Potential hazards can include air contaminants, and chemical, biological, physical, and ergonomic hazards.
Air Contaminants:
These are commonly classified as either particulate or gas and vapor contaminants. The most common particulate contaminants include dusts, fumes, mists, aerosols, and fibers.
Dusts are solid particles generated by handling, crushing, grinding, colliding, exploding, and heating organic or inorganic materials such as rock, ore, metal, coal, wood, and grain
Fumes are formed when material from a volatilized solid condenses in cool air. In most cases, the solid particles resulting from the condensation react with air to form an oxide.
The term mist is applied to liquid suspended in the atmosphere. Mists are generated by liquids condensing from a vapor back to a liquid or by a liquid being dispersed by splashing or atomizing. Aerosols are also a form of a mist characterized by highly respirable, minute liquid particles.
Fibers are solid particles whose length is several times greater than their diameter, such as asbestos.
Chemical Hazards:![]()
Harmful chemical compounds in the form of solids, liquids, gases, mists, dusts, fumes, and vapors exert toxic effects by inhalation (breathing), absorption (through direct contact with the skin), or ingestion (eating or drinking). Airborne chemical hazards exist as concentrations of mists, vapors, gases, fumes, or solids. Some are toxic through inhalation and some of them irritate the skin on contact; some can be toxic by absorption through the skin or through ingestion, and some are corrosive to living tissue.
The degree of worker risk from exposure to any given substance depends on the nature and potency of the toxic effects and the magnitude and duration of exposure. Information on the risk to workers from chemical hazards can be obtained from the Material Safety Data Sheet (MSDS) that OSHA’s Hazard Communication Standard requires be supplied by the manufacturer or importer to the purchaser of all hazardous materials. The MSDS is a summary of the important health, safety, and toxicological information on the chemical or the mixture’s ingredients.
Biological Hazards:
These include bacteria, viruses, fungi, and other living organisms that can cause acute and chronic infections by entering the body either directly or through breaks in the skin. Occupations that deal with plants or animals or their products or with food and food processing may expose workers to biological hazards. Laboratory and medical personnel also can be exposed to biological hazards. Any occupations that result in contact with bodily fluids pose a risk to workers from biological hazards.
In occupations where animals are involved, biological hazards are dealt with by preventing and controlling diseases in the animal population as well as properly caring for and handling infected animals. Also, effective personal hygiene, particularly proper attention to minor cuts and scratches especially on the hands and forearms, helps keep worker risks to a minimum.
Physical Hazards:![]()
These include excessive levels of ionizing and nonionizing electromagnetic radiation, noise, vibration, illumination, and temperature.
Ergonomic Hazards:
The science of ergonomics studies and evaluates a full range of tasks including, but not limited to, lifting, holding, pushing, walking, and reaching. Many ergonomic problems result from technological changes such as increased assembly line speeds, adding specialized tasks, and increased repetition; some problems arise from poorly designed job tasks. Any of those conditions can cause ergonomic hazards such as excessive vibration and noise, eye strain, repetitive motion, and heavy lifting problems. Improperly designed tools or work areas also can be ergonomic hazards. Repetitive motions or repeated shocks over prolonged periods of time as in jobs involving sorting, assembling, and data entry can often cause irritation and inflammation of the tendon sheath of the hands and arms, a condition known as carpal tunnel syndrome.
Housekeeping:
Good housekeeping means cleanliness and good order of equipment and facilities in a workplace. It needs planning and co-operation. Housekeeping is the first step towards good occupational hygiene practice.
Cleanliness:
Regular cleaning of workplaces, equipment and devices should be carried out to ensure an adequate level of workplace hygiene. A designated person should be assigned the responsibility to oversee such operations.
Rubbish or waste should be kept in suitable containers or litter-bins which are located at convenient locations in the workplace. The containers should be emptied daily, preferably near the end of each working day. Accumulation of dirt and refuse within the workplaces must be avoided. They should be removed with a suitable method from the floor or work benches regularly with frequency compatible with the nature of the work conducted. Floor cleaning can be done by washing, sweeping, vacuum cleaning or other appropriate means.
Floor covering materials should be suitable for the work and easy to clean.
The conditions of housekeeping can be easily assessed by visual observations. Records of maintenance work must be kept for evaluation of the performance, including information on the responsible person(s), contact and date/time of the action taken.
Tidiness:
Tidiness improves work performance and reduces accident. Equipment, tools, containers and small items on work benches should be kept neat and arranged in an orderly fashion. Sufficient space for storage of articles and goods is important.
The tools and material should be kept neat and in an orderly fashion.
Accident prevention:
The occurrence of accidents in a workplace could lead to damage to employees’ health and in severe cases death. Precautions must be taken when dangerous substances are stored or used. Containers should be clearly labelled and the labels easily visible. Regular maintenance and checking of the equipment and devices can reduce risks. The storage and disposal of chemicals or hazardous wastes should be done carefully. Accidental spillage and spread of waste or contaminants can be avoided through proper assignment of duties, instruction, training and good housekeeping.
- Chemicals without proper labeling may be misused and cause tragedy.
- A properly designed label provides readily available information which will prevent mishaps.
General ventilation:
Ventilation is the process of supplying and removing air by natural or mechanical means to and from a workplace. The term “natural ventilation” covers both the uncontrolled inward air leakage through cracks, windows, door ways and vents (infiltration) as well as the air leaving the room (ex filtration) through the same routes. Infiltration and ex filtration are often affected by the weather and are beyond control.
As a consequence, it is not feasible to rely upon natural ventilation to control emissions of dust and fumes. However, modest heat loads and very lowest emissions of gases and vapors could be effectively controlled by this system.
Mechanical or forced ventilation is provided by air movers or fans in a system such as a window mounted exhaust fan. It promotes the supply as well as the exhaust airflow.
Provision of fresh air supply:
It is essential to ensure that adequate ventilation is provided to a workplace, especially in an enclosed building. General ventilation is designed to provide fresh air for breathing by the occupants, control of thermal conditions and keeping the air free from contaminants (such as tobacco smoke, body odor and other air-borne contaminants). The fresh air intake points of aventilation system should be away from any source of contaminants. Filtration or cleaning of the incoming air before being supplied to a workplace is recommended.
In the planning stage of a building , the ventilation design should meet the minimum requirements of the Building (Ventilating Systems) Regulations. The Labour Department has also published a booklet called “Guidance Notes on Ventilation & Maintenance of Ventilation Systems” from which employers and employees can also find useful information for design of a work process and improvement of their ventilation system.
The fresh air supply rate required for a workplace varies with the nature of the activities and the degree of occupancy.
Monitoring of the ventilation system:
In a workplace without a specific source of contamination, the adequacy of ventilation can be measured indirectly with a carbon dioxide index method. As the concentration of carbon dioxide increase with human activities, background levels of other contaminants also increase. Carbon dioxide level frequently exceeding 1000 ppm (although carbon dioxide at such level is not a health concern) could be a useful indicator for review of the fresh air supply rate, distribution and the activities going on, especially when there is a complaint.
Carbon dioxide can be measured with either a direct-reading meter or detector tube kit. The relative occupancy, air damper setting and weather should be noted for each period of carbon dioxide measurement. The measurement should be made when concentration are expected to peak. If the occupant population is fairly stable during normal business hours, carbon dioxide levels will typically rise during the morning, fall during the lunch period, then rise again, reaching a peak in mid afternoon. In this case, sampling in the mid- to late-afternoon is recommended. It is helpful to compare measurement taken at different times of a day. Other sampling times may be necessary for different occupancy schedules. Individual measurements may be short-term .
Precautions in taking the measurement:
- measured away from any source that could directly influence the reading (e.g., hold the sampling device away from exhaled breath).
- preferably measured at head height.
Thermal conditions:![]()
Thermal conditions for enclosed workplaces should be commensurate with the activities in the area. The factors affecting these conditions include air temperature, humidity and air movement.
In naturally ventilated workplaces, for the best productivity / relative comfort, the optimum effective temperature (footnote) is below 27. For workplaces where room temperature control is difficult and where the effective temperature is likely to significantly exceed the recommended value, heat stress problems are likely and should be assessed. When continuous strenuous work is required to be carried out in a hot environment, other improvements should also be considered, including for example, suitable clothing, activity break period, supply of drinking water etc.
In an indoor work environment, the lower air temperature is preferably maintained at 16 or above.
For air-conditioned workplaces, when the range of room temperature for normal activities can be maintained between 20- 26, and relative humidity between 40% and 70%, the conditions are usually satisfactory. It provides optimum comfort and restricts the growth of micro-organisms. The upper temperature range of 23 – 26 is preferable for summer and the lower temperature range of 20- 24 is for winter. Supply of fresh air to an airconditioned area is particularly important as most of the indoor air is being re-circulated through the system. Maintenance of the system is also required because it often becomes the source of contamination when not properly maintained.
The installation of artificial ventilation should not expose employees to draughts which may cause discomfort. Similar problem may occur when the pressure among workrooms are not well balanced.
Control of biological contaminants:
In practical terms, employers have a duty to undertake proper house-keeping to avoid biological contamination and mould/bacteria growth inside buildings.The proper maintenance of the air conditioning system and fresh air supply can remove unpleasant odour and may prevent air-borne diseases.
For clinics, hospitals and health care institutions, there should be additional requirements for proper disposal of clinical wastes and adequate facilities, and proper systems for control of biological contaminants. In some situations, the employer or management should have an operating manual so that his employees can follow the instructions carefully.
Physical barriers:
Hazardous operations (e.g. a printing job being done in an office) should be separated from other activities by physical barriers partially or completely to prevent the spread and accumulation of air-borne contaminants into the normal working area. Other means of control should be provided in the (printing) area for the protection of the employees.
Mechanical ventilation:
To prevent accumulation of air-borne contaminants in the work area, mechanical exhaust ventilation is required to remove the impurities in air and to discharge them properly. Sufficient make-up air should be provided to facilitate the removal of contaminated air.
Local exhaust ventilation:
In specially hazardous operations, a local exhaust system may be required to effectively control atmospheric contamination at its source. A local exhaust system should normally contain an enclosing hood, ducting, an air cleaner and an exhaust fan.
To ensure effective control, the hood opening should be installed and used as close as reasonably practicable to the source of contaminants. The arrangement of positioning the hood so that it can enclose or confine the contaminant is recommended.
A local exhaust hood should enclose the source of contamination as far as practicable.
If installation of a fixed local exhaust system is not feasible, a mobile system with a suitable filter should be considered.
Lighting:
Daylight is the best and cheapest source of illumination. It can reduce energy costs but should be planned in the early stage of building design to maximize its application (Please refer also to the Building (Planning) Regulations for the minimum requirements) Making improvements in the later stage may be costly.
The distribution of light in a workplace can be improved by using more daylight. To get more daylight, people may rearrange their work orientation or the location of machines, or increase the size of windows or have windows placed higher up to take advantage of more daylight.
Windows and openings may be protected from direct sunlight by curtains or blinds to avoid glare and direct heat from the sun.
The use of artificial light and natural light is complementary. Their combined use is most economical and effective. It creates a sense of openness.
Lighting provision:
In workplaces, the artificial lighting provided should be such that there is no risk of accident to all employees (too dim), nor should it be damaging to their eyesight such as causing glare (too bright) or visual fatigue.
- When the intensity of lighting in a workplace is insufficient, the first consideration on improvement is to use light colors for walls and ceilings to increase the amount of reflected light. A white surface can have over 80% – 90% reflective. A pale tint for walls can have reflective up to 50 – 85%.
- Sufficient lighting improves employees comfort and performance. Combining the use of natural light and artificial lighting is the best mode.
- Old people need more light. For example, an employee aged 60 needs five times more
light to read a printed text than a 20-year-old one.
The time available for viewing the task affects the requirement of lighting too. The higher the speed of the task is, the higher the lighting level should be. Local lighting is recommended for precision or inspection work. Local lights that are easy to move and arrange in the desired positions are recommended.
Glare effect:
Glare effect can cause discomfort (often from reflective surfaces) and reduced visibility (often from a broad band source of white light perceived when facing a window). It reduces the ability to see and should be eliminated. A comfortable workplace should have no glare.
- Glossy or shiny materials or paint for wall and surfaces should be avoided to prevent indirect glare.
- Sometimes, the desk top may reflect the light sources at the ceiling or at the front to the users. To avoid the indirect glare effect, you may have to re-arrange the position of the work station or relocate light sources or provide shields to eliminate the problem.
- Direct glare can be removed by avoiding bright light sources falling within the normal field of vision. Mounting local lights high enough and shading them well to hide all bulbs can improve the situation. The use of naked light bulbs or fluorescent tubes is not recommended.
- The glare effect from windows or neighbouring work stations can affect visibility. It can be prevented by using curtains, blinds, partitions or desk-top partitions.
- Lighting provision at higher positions gives better dispersion and prevents glare.
- Older people are more sensitive to glare. They often need better lighting arrangements.
Contrast:
Changing the view from a bright area to a dark area demands adaption of the eyes. It takes time and is often tiring if the difference (contrast) is significant. It is recommended that the contrast between the job (target) and the immediate background should be no more than 10:3, and that between the target and its surrounding environment should be no more than 10:1.
The workplace should be lit up gently and evenly to minimize changes in brightness. Sharp shadows on the work surface are a reason for poor performance, eye strain,fatigue and sometimes accidents. Shadow zones should be eliminated by providing good distribution of lights as well as enhancing reflection from the walls and the ceiling.
In case there is a bright light source falling within the normal field of vision, the contrast can be reduced by providing more light for the environment.
Floors and drainage:
Some activities in a workplace are liable to make the floors or wall surfaces wet. An effective drainage system should be provided so that water can be removed and drained quickly from the floor. This prevents the floor from causing slips and accidents, and reduces the flourishing growth of mould and other micro-organisms.
Floor condition:
The floor should be maintained clean, stable and non-slippery. For workplaces where wetting of the floor is unavoidable, the tiles should be made of non-slippery material. Alternatively, a foot platform may be provided for employees to stay away from the wet surface. Moreover, the drainage should be well maintained and under no circumstances should dirt be allowed to accumulate underneath the platform or the corners of the shop floor.
Lavatories and washing facilities:
Suitable and sufficient sanitary conveniences and wash basins should be provided at readily accessible places. They are supposed to be adjacent to but separate from other sanitary facilities such as changing rooms and shower facilities.
- Sanitary facilities should be provided for men and women separately.
- The facilities must be maintained tidy, clean and hygienic. Daily cleaning is recommended.
- The number of water closets and related facilities for employees should follow the recommendations in the Building
The conditions of cleanliness of the sanitary facilities should be inspected regularly (e.g. weekly) by an appointed personnel. Breakdowns of the units, blockage of the pipes or leakage should be reported immediately for repair. The records should be counter-checked and signed by the management or a responsible person.
Changing rooms and shower facilities:
When the activities in the workplace are likely to produce bodily contamination, an adequate, suitable and secure place should be provided for employees to store their own clothing and work clothing.
Changing rooms should be equipped with lockers. To maintain good personal hygiene, showers with hot and cold or warm water supply are required and should be readily accessible from work rooms.
When a highly dangerous operation is carried out in a workplace, an emergency shower or eye washers should be provided at suitable locations. All the facilities should be properly maintained and be kept sanitary for use in emergency situations.
Drinking water supply:
Employers have a duty to provide an adequate supply of drinking water. Good drinking facilities and rest places can do much to prevent fatigue and to maintain employees’ health. It is especially important in a hot environment.
The supply of drinking water facilities or wholesome drinking water such as tap water or drinking fountains should be easy to access. However, such facilities should not be near dangerous machines nor contamination sources, nor in washrooms or toilets.
Bottled drinking water or other beverages can be alternatives to drinking water facilities. They are hygienic and require the least maintenance.
In a hot environment or summer, it isimportant to provide cool water. If there is no water cooling device, the water containers can be placed in a cool location of the workplace.