Environmental Hazards of Chemicals: Health Effects, Chemical Handling and Chemical Safety!
Health Effects of Chemicals on Human Body:
The physical form of a chemical can affect how it enters your body and to some extent, the damage it causes.
The main physical forms of chemicals are solids, dusts, liquids, vapours and gases:
ADVERTISEMENTS:
1. Solids are the least likely of the chemical forms to cause chemical poisoning. However, certain chemical solids can cause poisoning if they get onto your skin or food and you then ingest them.
2. The greatest danger with solids is that some work processes can change them into a more dangerous form. For example, wood that is being cut can turn into wood dust which can then be inhaled. Welding rods can decompose into fumes and gases. Polyurethane foam is safe in its normal solid form but gives off deadly gases, if it bums.
3. Chemicals in solid form can give off toxic vapours which can be inhaled, and solids can be flammable and explosive, and corrosive to the skin.
4. Effective control measures should be used with chemical solids, particularly during work processes which may change them into more hazardous materials.
ADVERTISEMENTS:
1. You can be exposed to dust in the workplace from materials that normally exist in dust form (for example, bags of cement), or from work processes that create dust (for example, handling glass fibre can produce toxic dust).
2. The main danger from harmful dusts is that you can breathe (inhale) them into your lungs. When breathed in the larger dust particles are usually trapped by hasal hairs and mucus and then removed by the body. Smaller particles, however, are more dangerous because they can get deep inside the lungs where they can have damaging effects, or they can be absorbed into the bloodstream and travel to other parts of the body where they can cause damage. They can also cause eye damage.
3. Dusts can be hard to see – you often cannot even see a cloud of tiny dust particles except with special lighting. Particles less than 40 microns are not visible to naked eye.
4. Under certain conditions dusts can explode. An example of this is an explosion in a grain silo, flour mill or coal grinding ball mills.
ADVERTISEMENTS:
5. Effective control measures should be used to keep dust in the workplace at “safe” levels.
1. Many hazardous substances, such as acids and solvents, are liquids when they are at normal temperature.
2. Many liquid chemicals give off vapours which you can inhale and which may be highly toxic, depending on the chemical.
ADVERTISEMENTS:
3. Liquid chemicals can be absorbed by skin. Some liquid chemicals may cause immediate skin damage (they may or may not be absorbed into the bloodstream as well). Other liquids pass directly through the skin into the bloodstream, where they can travel to different parts of the body and cause damaging effects.
4. Effective control measures should be used with liquid chemicals to eliminate or reduce the possibility of inhalation, skin exposure and eye damage.
1. A vapour is the gas phase of a material which is normally liquid under standard conditions.
2. Tiny droplets of liquid which are suspended in the air are called mists.
3. Many liquid chemicals evaporate at room temperature, which actually means that they form a vapour and stay in the air.
4. The vapours from some chemicals can irritate your eyes and skin.
5. There can be a variety of serious health effects from inhaling certain toxic chemical vapours.
6. Vapours can be flammable or explosive. To avoid fire or explosion, it is important to keep chemicals that vaporize away from any sparks, sources of ignition or incompatible chemicals.
7. Controls should be used to prevent worker exposure to vapours from liquids, solids or other chemical forms.
8. Gasoline and water are two examples of liquids which generate vapour under standard conditions.
1. Some chemical substances are in the form of a gas when they are at a normal temperature. However, some chemicals in liquid or solid form become gases when they are heated.
2. You can detect some gases easily by their colour or smell, but there are other gases that you cannot see or smell at all – you can only detect them with special equipment.
3. Gases can be inhaled.
4. Some gases produce irritant effects immediately. The health effects of other gases may be noticeable only after your health has already been seriously damaged. Gases may be flammable or explosive. Extreme caution should be used when working around flammable or explosive gases.
5. Workers should be protected from the potential harmful effects of chemical gases with effective control measures in the workplace.
6. Some examples of gases are: nitrogen, nitrogen dioxide, carbon monoxide, carbon dioxide, and oxygen.
Biochemical Actions of Chemicals:
There are a number of factors that determine the type of toxic effect a chemical can have on you.
These Factors Include:
(i) The chemical composition of the hazardous substance (certain substances are more harmful than others because of their chemical structure);
(ii) The physical form of the chemical (dust, vapour, liquid, etc.);
(iii) The route of entry by which the chemical gets into the body (chemicals have different routes of entry. Some chemicals can enter the body in more than one way. Different health effects can occur depending on the route of entry);
(iv) The particular tissues and organs in which the chemical collects or localizes;
(v) The frequency, concentration, and length of exposure; and
(vi) The worker’s individual response to the chemical, which can vary a great deal from person to person.
The Chemicals Produce a Variety of Health Effects Including:
(i) Irritant or Corrosive:
As the name implies, these chemicals can cause inflammation and/or blistering of the skin. Short-term exposure frequently heals whereas long-term exposure can lead to permanent damage (chemicals examples- ammonia, sulphuric acid, and caustic soda);
(ii) Allergenic:
For susceptible workers, these chemicals produce asthma-like symptoms (lungs) or industrial dermatitis (skin) [examples include toluene diisocyanate- TDI, epoxy resins, formaldehyde];
(iii) Fibrogenic:
These chemicals result in the gradual cumulative loss of lung function as “elastic” alveolar tissues are damaged by dust. Virtually any dust can have this effect;
(vi) Asphyxiant:
These are chemicals which stop the normal absorption of oxygen by the body either by replacing the oxygen or inhibiting its uptake. The gases, carbon dioxide and carbon monoxide, are examples;
(vii) Narcosis:
Chemicals such as a number of solvents which depress the central nervous system and produce “light headedness” which can be a factor in accidents;
(viii) Poisonous:
These chemicals cause damage/death of cells in vital organs leading to the failure of that organ to function effectively which can ultimately lead to death;
(ix) Carcinogenic:
These chemicals cause cancer in exposed workers usually over a long period of time.
Examples include – arsenic, asbestos, chromium, nickel, 2- napthylamine, etc.
(x) Teratogenic and Mutagenic:
These chemicals affect the foetus in the womb or eggs/sperm for future generations.
Carcinogens are cancer-causing compounds.
Some chemicals are known human carcinogens, others are only suspected as carcinogens.
DOSH has regulations covering the general use of carcinogens, and has specific regulations for several known human carcinogens.
DOSH Has Specific Regulations on the Following Carcinogens:
1. Vinyl Chloride
2. Acrylonitrile
3. 1, 2, -Dibromo-3-chloropropane (DBCP)
4. Arsenic
5. Ethylene Oxide
6. Cadmium
7. Butadiene
8. Methylene Chloride
9. Benzene
10. Hexavalent Chromium
Other Groups of Toxic Chemicals:
Teratogens are compounds that can harm the developing fetus, causing birth defects or death.
Mutagens cause genetic mutations or changes. These mutations can cause’ birth defects or other problems in following generations or may lead to cancer in the exposed person. Sensitizers can “switch on” a reaction in an individual worker. The reaction to a sensitizer depends upon the individual worker.
Once a worker becomes sensitized to a compound, smaller and smaller exposures can cause a reaction, and the reactions can become more severe.
(i) Dose- The effects of any toxic chemical depend on the amount of a chemical that actually enters the body.
(ii) Acute Toxicity- The measure of how toxic a chemical is in a single dose over a short period of time.
(iii) Chronic Toxicity- the measure of the toxicity of exposure to a chemical over a long period of time. Some chemicals will only make you sick if you get an “acute” or high dose all at once. Example- ammonia
Some chemicals are mainly known for their chronic or long-term effects. Example- asbestos.
Most chemicals have both acute and chronic effects. Example- carbon monoxide.
The health risk is dependent upon the toxicity of the chemical, the types of effects and the various routes of entry.
Toxicity, Vs. Hazard of Chemicals:
(a) Toxicity is ability of a chemical to act as a poison or cause injury to tissues.
(b) Hazard is likelihood that a chemical will cause injury in a given environment or situation; degree of hazard depends on how toxic the substance is, how it is absorbed, etc.
(a) Acute Exposures means exposure of short duration, usually to relatively high concentrations or amounts of material.
(b) Chronic Exposures means continuous or intermittent exposure extending over a long period, usually to relatively low material amounts or concentrations.
Local Vs. Systemic Effects:
(a) Local effects of the chemical may be localized on a specific area of the body such as nose or throat.
(b) Systemic Effects means entire body system and organs are affected.
Exposure to toxic chemicals can also lead to higher rates of accidents at work. For example, chemicals such as solvents and asphyxiates may slow your reaction time by affecting nervous system or limiting the amount of oxygen that gets to lungs. A slow reaction can be very serious (or even fatal) if you are in a dangerous situation that requires an immediate response.
Unfortunately, when accidents occur in the workplace, management often blames the worker, claiming he or she was careless. This tendency to “blame the victim” is yet another reason to learn about the substances you work with, to make sure the proper control measures are in place, and to know your rights.
Many chemicals have exposure limits, or allowable amounts of a chemical in the air.
These limits are often called “permissible Exposure Limits (PEL)” or Threshold limit Values (TLV)” or “Recommended exposure Limits (RELs)”, or, “Time weighted Averages (TWA)” based on 8-hour average exposure – Short Term Exposure Limits (STEL)” or ceiling or peak levels.
Chemicals exposure Levels must be kept below these limits for safety.
The NIOSH recommended exposure limits (RELs). For NIOSH RELs, “TWA” indicates a time- weighted average concentration for up to a 10-hour workday during a 40-hour workweek. A short-term exposure limit (STEL) is designated by “ST” preceding the value; unless noted otherwise the STEL is a 15-minute TWA exposure that should not be exceeded at any time during a workday.
A ceiling REL is designated by “C” preceding the value; unless noted otherwise, the ceiling value should not be exceeded at any time. Any substance that NIOSH considers to be a potential occupational carcinogen is designated by the notation “Ca”. Keep them away from heat, sparks, or flames. Friction from rubbing objects together may produce enough heat or sparks to ignite these materials.
If you need to heat flammable solvents, use Standard Methods of Prevention:
1. Incompatible Materials:
Keep incompatible chemicals away from each other. For example, don’t place strong acid solutions near strong bases, peroxides near organic solvents, bleach near chlorine, etc. When mining materials, such as oxidizers and reducers, or acids and bases, dilute them first.
2. Avoid Contact:
Protect your five routes of entry. Wear suitable PPE. Eye protection must be worn when you handle chemicals. Avoid skin contact. Wear compatible gloves if you are going to use organic solvents or flammable or combustible liquids. Wear an apron when handling corrosive materials. Use appropriate engineering controls, such as a hood, if there is a risk of inhaling fumes or dust. Keep containers tightly sealed.
3. Hygiene:
Keep yourself clean of chemicals:
Keep everything away from your face to prevent contact with your mouth and eyes. No smoking, eating, drinking, or applying makeup or lip balm. No mouth pipetting- attach approved bulbs or other devices to the pipet. Keep pens, pencils, and your fingers away from your face.
Assume your hands are contaminated, even if you wear gloves. Wash your hands frequently and upon leaving the laboratory.
(i) Clean up chemical spills promptly. They tend to migrate if left alone, and they can contaminate other areas.
(ii) Remove soiled gloves, lab coats, aprons, etc., before leaving the laboratory.
(iii) Tie back long hair, clip or remove neckties, arid avoid wearing dangling jewelry. You don’t want these items to fall into chemicals or touch an open flame. They may also get tangled in vacuum pump motors and other moving parts.
4. Transporting Chemicals:
When transporting chemicals between the storage area and your workplace, put containers in protective carrying devices. Glass bottles can break if they bump against a wall, door, or other obstruction. Carry only what you can hold in your hands.
Don’t hug several jars or bottles near your body; you may drop something, or someone may walk into you and break a container. If you have a lot to carry, use a cart with a rim on each shelf. Keep containers in protective devices so they won’t rattle or tip. Don’t transport incompatible chemicals together.
Chemical Handling:
Review the following list from time to time to check your own knowledge of the safe handling of chemicals:
1. Be Careful:
Watch where you place containers, and close them when you have finished. Read the label to be sure that you’re working with the right materials. For example, there’s a big difference between sodium thiosulfate and sodium thiosulfate. Don’t rush — that’s when you’re more likely to spill or make a mistake.
2. Stay Alert:
Fatigue affects judgment. You need to focus your attention on a number of different procedures and assignments. Often you’re rushing to meet deadlines. If you need to work extra hours, take periodic breaks. Be careful not to leave anything unattended if it creates a hazardous situation.
If you take prescription medication that causes fatigue, avoid handling hazardous chemicals or equipment. If you are unable to concentrate, or if you feel fatigued or confused, speak to your supervisor immediately. You may be affected by an overexposure and not be aware of it.
3. Follow Directions:
Make sure you know the correct procedures, and any associated hazards, for any analysis you perform or technique you use. Sometimes larger quantities of materials may require additional precautions or different procedures. Some exothermic reactions may generate too much heat or may explode if scaled-up. You may need different equipment or more engineering controls. When working on a new technique or synthesizing a new compound, discuss any new activities with your supervisor.
4. Monitor Heating:
Monitor any reactions you are heating. They may boil over, or the solvent may evaporate. Check water or oil levels in temperature baths. Many liquids, solids and gases are flammable.
5. Know what you’re working with:
Read material safety data sheets (MSDSs) and container labels for all chemicals. Know how the chemicals can hurt you, how to avoid harmful conditions in your work area, and how to respond to an accident.
6. Think about what you’re doing:
It’s easy to develop a routine and habits in your work. Even though you’ve used a particular procedure for years, you should still pay close attention to what you’re doing. Accidents are more likely to occur when your level of concentration is low especially early in your career, they stay with you, and you’re more likely to stay healthy.
7. Follow All Safety Procedures:
Obey the warning signs posted in your lab and follow the directions and precautions on chemical labels. Use engineering controls as they are intended. Use a hood if fumes or dust will be released. Use a shield for protection against splashes or explosion. Always wear approved eye protection and the PPE required for the chemicals you are handling.
8. Practice Good Housekeeping and Personal Hygiene:
Keep your work area clean and free of chemical residues. Wash your hands frequently, even if you wear gloves while handling chemicals. Remove protective clothing when you leave the lab (including lab coats and aprons). Make sure all contaminated clothing is properly cleaned.
9. Report Dangerous Activities or Situations:
Pay attention to the way other workers handle hazardous materials. Someone else’s mistake can hurt you. Take care of any frayed wires, spills, non-labeled containers, or malfunctioning equipment. If you can’t handle the situation alone, talk to your supervisor. These hazards won’t take care of themselves and could lead to injury.
Review the following list from time to time to check your own knowledge of the safe handling of chemicals:
(i) Be Careful:
Watch where you place containers, and close them when you are finished. Read the label to be sure you’re working with the right materials. For example, there’s a big difference between sodium thiosulfate and sodium thiosulfate. Don’t rush – that’s when you’re more likely to spill or make a mistake.
(ii) Stay Alert:
Fatigue affects judgment. You need to focus your attention on a number of different procedures and assignments. Often you’re rushing to meet deadlines. If you need to work extra hours, take periodic breaks. Be careful not to leave anything unattended if it creates a hazardous situation.
If you take prescription medication that causes fatigue, avoid handling hazardous chemicals or equipment. If you are unable to concentrate, or if you feel fatigued or confused, speak to your supervisor immediately you may be affected by an overexposure and not be aware of it.
(iii) Follow Directions:
Make sure you know the correct procedures, and any associated hazards, for any analysis you perform or technique you use. Sometimes larger quantities of materials may require additional precautions or different procedures.
Some exothermic reactions may generate too much heat or may explode if scaled-up. You may need different equipment or more engineering controls. When working on a new technique or synthesizing a new compound, discuss any new activities with your supervisor.
TWA concentrations for OSHA PELs must not be exceeded during any 8-hour work shift of a 40-hour workweek. A STEL is designated by “ST” preceding the value and is measured over a 15-minute period unless noted otherwise. OSHA ceiling concentrations (designated by “C” preceding the value) must not be exceeded during any part of the workday; if instantaneous monitoring is not feasible, the ceiling must be assessed as a 15-minute TWA exposure.
In addition, there are a number of substances from e.g., beryllium, ethylene dibromide that have PEL ceiling values that must not be exceeded except for specified excursions. For example, a “5-minute maximum peak in any 2 hours” means that a 5-minute exposure above the ceiling value, but never above the maximum peak, is allowed in any 2 hours during an 8-hour workday.
Concentrations are given in ppm, mg/m3, mppcf (millions of particles per cubic foot of air as determined from counting an impinger sample), or fibers/cm3 (fibers per cubic centimeter). The “[skin]” designation indicates the potential for dermal absorption; skin exposure should be prevented as necessary through the use of good work practices, gloves, coveralls, goggles, and other appropriate equipment. The “(total)” designation indicates that the REL or PEL listed is for “total particulate” versus the “(resp)” designation which refers to the “respirable fraction” of the airborne particulate.
Chemical Health Risk Assessment (CHRA):
Chemical Health Risk Assessment (CHRA) is corner stone on which compliance with the Use and Standard of Exposure of Chemicals Hazardous to Health (USECHH) Regulations 2000 is achieved. USECHH Regulations require employer to make a comprehensive assessment of the risk of employees exposure to chemical hazardous to health in the workplace for the purpose of enabling decision to be made on appropriate control, measure, further training of employee, and monitoring health surveillance activities as may be required to protect the health of employees who may be exposed to chemical hazardous to health at work.
NIOSH offer comprehensive CHRA services in providing guidance on improving current control measure Complete with report and the recommendation in accordance to USECHH 2000.
Common Laboratory Safety Practices:
Your laboratory will have policies for your specific activities but all laboratories follow these common safety practices:
Think Safety First:
Review the procedures you will use, and look for potential hazards from chemicals and equipment Plan your work. Determine what protection you need, such as engineering controls and equipment, personal protective equipment, and safe procedures and gases are flammable. Keep them away from heat, sparks, or flames. Friction from rubbing objects together may produce enough heat or sparks to ignite these materials. If you need to heat flammable solvents, use Standard Methods of Prevention.
Incompatible Materials:
Keep incompatible chemicals away from each other. For example, don’t place strong acid solutions near strong bases, peroxides near organic solvents, bleach near chlorine, etc. When mixing materials, such as oxidizers and reducers, or acids and bases, dilute them first.
Avoid Contact:
Protect your five routes of entry. Wear suitable PPE (personal protective equipment’s) Eye protection must be worn when you handle chemicals. Avoid skin contact. Wear compatible gloves if you are going to use organic solvents or flammable or combustible liquids. Wear an apron when handling corrosive materials. Use appropriate engineering controls, such as a hood, if there is a risk of inhaling fumes or dust. Keep containers tightly sealed.
Hygiene:
Keep yourself clean of chemicals:
(i) Keep everything away from your face to prevent contact with your mouth and eyes. No smoking, eating, drinking or applying makeup or lip balm. No mouth pipeting; attach approved bulbs or other devices to the pipet. Keep pens, pencils, and your fingers away from your face.
(ii) Assume your hands are contaminated, even if you wear gloves. Wash your hands frequently and upon leaving the laboratory.
(iii) Clean up chemical spills promptly. They tend to migrate if left alone, and they can contaminate other areas.
(iv) Remove soiled gloves, lab coats, aprons, etc., before leaving the laboratory.
(v) Tie back long hair, clip or remove neckties, and avoid wearing dangling jewelry. You don’t want these items to fall into chemicals or touch an open flame. They may also get tangled in vacuum pump motors and other moving parts.
(vi) Transporting chemicals- When transporting chemicals between the storage area and your workplace, put containers in protective carrying devices. Glass bottles can break if they bump against a wall, door, or other obstruction. Carry only what you can hold in your hands.
Don’t hug several jars or bottles near your body; you may drop something, or someone may walk into you and break a container. If you have a lot to carry, use a cart with a rim on each shelf. Keep containers in protective devices so they won’t rattle or tip. Don’t transport incompatible chemicals together.
Hazardous Concentrations of Chemicals are represented by Following Parameters:
1. IDLH (Immediate danger to life and health)
2. LD50 (Lethal dose 50)
3. LC50 (Lethal concentration 50)
4. TLV (Threshold Limit Value)
5. TWA (Time weighted Average)
6. STEL (Short term Exposure Limit)
7. PEL (Permissible Exposure Limit)
8. REL (Recommended Exposure Limit)
Control Methods for Chemical Hazards:
Control of chemicals in the workplace should be according to the following hierarchy of priorities:
(a) Elimination of the most toxic materials.
(b) Substitution of hazardous materials by less hazardous ones.
(c) Containment, or total enclosure of toxic processes or substances.
(d) Adoption of safe handling procedures.
(e) Exhaust ventilation, using efficient hoods, ducting, filters, and fume cupboards, and noise-controlled fans or suction devices.
(f) Environmental monitoring – fixed point, grab sampling and/or personal monitoring – should always accompany containment and ventilation control measures, to monitor their effectiveness.
This is an area assigned for the usage of either a particularly hazardous substance or purpose. For example, if carcinogens are being used in the lab, a “designated area” should be assigned, and warning label should be posted.
There are no longer clean areas allowed in an active research laboratory.
This is the most effective and desirable method for minimizing risk of exposure either to toxic chemicals or to mechanical equipment. Examples of engineering controls: guards, remote controls, or interlock systems. However, for toxic fumes, mists, and vapors, ventilation systems are the best approaches to help reduce personal exposure to acceptable levels.
Generally, there are two types of ventilation systems:
In most buildings a certain percentage of the building air is recirculate periodically through the building ventilation systems but in laboratories all air is exhausted directly to the outside. This “single pass” system is a type of “dilution ventilation” system for controlling low risk airborne contaminants. They are simply exhausted to the outside before they can build to hazardous levels.
(b) Local Exhaust Ventilation:
Used for moderate to high-risk contaminants. Local exhaust systems capture the airborne contaminants much more effectively than dilution systems such as chemical fume hoods.
(i) Local exhaust ventilation (e.g. an exhaust hood) should be used to reduce solvent exposures during the spotting process. An exhaust hood should be located near the source of the spotting chemicals to prevent the vapors from entering the workers’ breathing zone. A slot hood at table level or a downdraft table exhausting to the outside of the building provides good protection for workers. Spotting tables equipped with an exhaust hood are now commercially available.
(ii) General ventilation should include both supply and exhaust air. Make-up air supply should be designed and used in conjunction with the exhaust system. An inadequate volume of makeup air may result in negative pressure areas, perhaps resulting in drafts that interfere with the exhaust hood.
When make-up air is introduced, it should enter the opposite side of the room from the exhaust to prevent short circuiting. Ventilation systems in dry cleaning shops should provide a minimum of 30 cubic feet per minute (cfm) of outside air per person.
(c) Fume Hood:
The fume hood is designed to contain and disperse gases, vapors, and aerosols to the external environment. It does not provide absolute containment or protection from the materials in the hoods, however, a properly designed hood in a properly designed room can provide adequate protection if the following practices are observed-
(i) Inspect and ensure that the hood is working.
(ii) Do not store chemicals and equipment in the hood.
(iii) Remove unnecessary chemicals and equipment.
(iv) All equipments should be at least 1.5 cms back from the front sash
(v) Position the sash no higher than the approved working height that is designated by a fluorescent yellow sticker.
(vi) When evaporating or distilling perchloric acid, special perchloric acid fume hoods must be used.
In most cases, a well-designed set of work practices is the best risk management tool:
(a) Chemical Transportation:
Assure that an unbreakable secondary container is being used, and that transport carts are designed for this purpose.
(b) Eating, Drinking and Smoking:
There should be no eating, drinking, smoking, chewing of gum or tobacco, application of cosmetics, storage of utensils, food, or food containers in the laboratories.
(c) Pipetting:
Mechanical pipetting aids should always be used for all pipetting procedures. Oral pipetting is prohibited.
(d) Personal Hygiene:
All personnel should wash their hands immediately after the completion of any procedure in which chemicals have been used and when they leave the laboratory. If hazardous chemical exposures occur to skin, immediately shower or wash affected areas.
(e) Housekeeping:
Keeping the working area clean and orderly reduces the frequency and severity of accidents.
Here are some common sense tips:
(i) Keep aisles, exits, stairs and hallways free of obstructions.
(ii) Avoid slip hazards by keeping the floor clean of ice, stoppers, glass beads or rods, other small items and spilled liquids.
(iii) Keep drawers and cabinet doors closed.
(iv) Never store chemicals on the floor.
(v) Workspaces and storage areas should be kept clear of broken glassware, leftover chemicals and scraps of paper.
(vi) Place all non-contaminated broken glass in rigid containers clearly marked “Broken Glass”.
Chemical Safety- Ten Basic Rules:
1. Know tie hazards of chemicals in use.
2. Label all chemicals and their waste properly.
3. Use PPE while handling hazardous chemicals.
4. Work with volatile and hazardous chemicals in a fume hood.
5. Store flammables properly.
6. Do not work alone with hazardous chemicals.
7. Maintain clear access to exits, showers and eyewashes
8. Keep work areas free to clutter.
9. Wash promptly when chemical contacts skin.
10. Do not eat, drink, and apply cosmetics in laboratory.
1. Recognition of Chemical Hazards:
It may sound obvious but how do you know if you have a chemical problem in your workplace? Some chemical hazards are obvious as in the case of an acid bum, accordingly you can come up with various control strategies for handling the acid. However, many chemical hazards are more insidious in their effect.
They do not produce any immediate, obvious effects on the workers and you may not be aware of the slow onset of any occupational disease. You may have a suspicion that something is wrong but be unsure about what to do.
In such cases, there a number of ways of ways to look into the problem:
(i) Direct health indicators – Are specific workers off sick more than others?
Has the company nurse or doctor seen an increase in ill health in certain groups of workers? Do any workers have obvious health effects from working with a specific chemical? Have the workers complained when using a specific chemical?
(ii) Experience/knowledge of a specific chemical- Managers should have approved Material Safety Data Sheets (MSDSs) for all chemicals used in their workplaces. These MSDSs are produced by the chemical manufacturers and, in many countries of the world, are required by law.
Warning properties, such as those shown below, are examples of characteristics that could alert you to the presence of a chemical in the air.
i. Odor threshold
ii. Color of product
iii. Other senses
i. Odor Threshold:
The odor threshold is the airborne concentration at which a hazardous chemical can be detected by smell. This concentration of gas or vapor is expressed as parts per million parts (ppm) of air.
This odor threshold is considered to be one of the warning properties of gases and vapors but must always be used with caution because of variations between individuals and their senses of smell. Allergies, head colds, and olfactory fatigue also can reduce one’s ability to smell.
ii. Color of Product:
Color can present a visual indication of the presence of a potentially hazardous chemical. Two examples are fuming nitric acid, which creates a red cloud, and chlorine gas, which has a greenish color. Both of these materials are highly toxic.
iii. Other Senses:
Mild irritation of the eyes, nose, or throat can be a useful warning property if it occurs at a concentration that does not produce other harmful or toxic effects. Some chemicals will produce a taste before, or instead of, odor or irritation.
(i) Ammonia is a good example of a chemical with a useful odor threshold. Some individuals can detect ammonia at 5 ppm which is below the average of 17ppm.
(ii) It is also 10 times lower than its OSHA Permissible Exposure Limit. (PPL) Since the odor threshold can warm you well before the Threshold Limit Value (TLV) and PEL are reached, ammonia is said to have adequate warning properties.
(iii) Another reference indicates that Methyl Formate has an odor threshold of 2, 000 ppm, which is 20 times higher than its PEL of 100 ppm. Thus, it is dangerous to rely on methyl formates odor as a warning property.
2. Evaluation of Chemical Hazards:
Evaluating or measuring the risk of chemicals is difficult. This normally involves taking air samples and comparing the level with recognized exposure limit standards. This is often time consuming, expensive and open to different interpretations. Often the equipment gives only a “qualitative” snap-shot value.
Evaluating the risk means ranking them as low, medium or high depending upon the toxicity of the chemical, duration of exposure type of exposure, use of PPE etc. Even though there are legal requirements in Cambodia relating to Air Pollution Control which specify the maximum allowable concentration of hazardous substances in ambient air, the enforcement agencies do not have the requisite equipment to measure chemicals in the workplace.
3. Control of Hazards:
Once you have recognized that you have a problem with a chemical hazard in the workplace, what can you do about it? For all health and safety problems, including chemical hazards, there is a logical, systematic strategy or sequence for dealing with them ranging from elimination to the use of personal protective equipment (PPE).
As the name implies, the most effective way of controlling chemical hazards, is by eliminating them from the process or by finding a safe substitute. Obviously if you can remove the chemical hazard from the workplace, you have solved the problem.
This however rarely occurs as the chemical in question is usually a vital part of the process or a natural by-product. The next best method is to use a safer substitute for the original chemical (this is best done by seeking advice from the competent authorities and by comparing the information for the different chemicals on their specific MSDSs.
Some examples of safe substitution could include:
(i) Use less hazardous solvents instead of toxic ones;
(ii) Use water and detergents instead of solvents for cleaning;
(iii) Use leadless glazes and paints.
Using safer substitutes does not mean the new chemical is safe – all it means is that it is safer than the original hazard.
There are a number of engineering measures (including enclosure, isolation and ventilation) that can be used to control chemical hazards either by partially or totally enclosing the process. Highly toxic materials that may be released into the workplace atmosphere should be totally enclosed, usually by using a mechanical handling device or a closed glove system that can be operated from the outside. If the process is particularly hazardous, it can also be isolated to other parts of the factory or separate rooms where there are fewer workers.
When using enclosure and isolation it is important to consider all aspects of ventilation. As we saw in the section on ventilation, general ventilation can be used to “dilute” chemical hazards in the workplace and local exhaust ventilation/partial enclosures can be used to remove more toxic chemical hazards to the outside of a factory.
Only as a last resort should workers are required to wear personal protective equipment- after all, by the use of PPE, we have admitted that we cannot control the hazard at source or along the pathway between the source and the worker. The use of PPE is the least efficient, but often the cheapest, method of control. PPE is often uncomfortable to wear, especially in the hot, humid conditions found in many workplaces and, it is not uncommon to find workers only wearing the PPE at the times of a visit by a Labour Inspector Officer.
Workers sometimes complain that wearing PPE inhibits their work performance and, in the case of hearing protection, can limit communication and prevent workers from hearing any warning signals. Examples of PPE include – safety glasses; ear muffs and plugs; respirators (different types for dusts, fumes, vapours etc.); gloves; safety shoes; helmets and hard hats; aprons and overalls. It is important that workers are provided with the correct type of PPE for the specific hazard and given training in its correct use.
Namely, how to ensure the best fit; how to avoid leaks; how to tell when it needs replacing; how to keep it clean and maintain the PPE etc. All too often however, you can see the workers wearing totally the wrong type of PPE or wearing it incorrectly e.g. dust masks only being worn over the mouth and not the nose as well. Another of the most common mistakes is to find workers wearing simple dust masks when dealing with a chemical vapour.
This can actually make them situation worse as the vapour is actually absorbed into the fabric of the dust mask (rather, like tissue absorbs a liquid or blotting paper absorbs ink) and then it remains in worker’s breathing zone for as long as he/she is wearing the mask. It must be emphasised again that the choice of PPE depends upon the nature of the hazard as well as the route and duration of exposure. The PPE must be the best available and not necessarily the cheapest- and it should not be improvised.
Other control methods can include administrative controls which means limiting the amount of time workers spend at a hazardous job thereby reducing exposure. Job rotation, changing work schedules are typical examples. It must be remembered that the hazard still exists so that any administrative measures must be used with other forms of control. Linked to administrative controls are the general cleanliness of the workplace and personal hygiene, both of which can reduce the exposure to chemical hazards.
Chemicals Hazards Communication should be done by informing the workers about:
(i) What are hazardous chemicals?
(ii) How hazardous chemicals affect the body?
(iii) What are the different types of hazardous chemicals?
(iv) What is on product labels?
(v) What are material safety data sheets?
(vi) How to protect yourself from hazardous chemicals?
Monitoring of Chemical Hazardous to Health:
Monitoring is to be conducted on employees’ exposure to chemical hazardous to health.
Workplace exposure monitoring also may be required for other reason such as:
(i) To ensure the employees’ exposure level are maintained below the Permissible Exposure Limits.
(ii) To ensure the maintenance of adequate control measure.
(iii) To quantify exposure during new process set-up.
(iv) To assess the effects of a change in process specification.
(v) To ensure that the risk assessment is still valid.
Control of basic Chemicals Hazards:
Substitution of Chemicals:
One means of preventing exposure is substitution with a safer chemical.
1, 1, 1-trichloroethane, which was widely used by small engineering companies in metal degreasing has been replaced with trichloroethylene (TCF). However TCE is more acutely toxic and carcinogenic, and has a significantly lower occupational exposure limit than 1, 1, 1-trichloroethane. Substitution is not about “shifting risks between workers, consumers or parts of the environment.”
The Montreal Protocol also banned CFC-114, which was used as a refrigerant. In one Belgian smelting plant, CFC-114 was replaced with an HCFC mixture in the air-conditioning unit of an overhead gantry cabin. After nine gantry drivers developed hepatitis, an occupational health doctor traced the cause to the new, more environmentally friendly coolant.
The new mixture contained HCFC-123, which had already been found to cause liver damage in rats. The drivers had been exposed to HCFC-123 at levels much higher than the occupational exposure limit because of a leaking hose in the air-conditioning system. The problem might have been noticed sooner if someone had realized that the unit must have been leaking because it needed to be refilled so often.
Biological monitoring is the measurement of the amount of a substance or its metabolite, or a biochemical effect, from which exposure can be assessed; Biological monitoring measures the amount of a substance that has been absorbed into the body, rather than measuring the amount that is present in the workplace air.
A variety of specimens can be used, such as urine, blood or exhaled air. For example, exposure to an organophosphate pesticide can be monitored either by measuring the amount of a metabolite in urine, or by measuring the activity of an enzyme (acetylcholinesterase) in the blood. Workplace exposure to over 100 different chemicals can be estimated by biological monitoring.
Health surveillance, which includes biological monitoring, is a collective term for a variety of procedures designed to protect workers’ health by early identification of exposure or disease. As well as biological monitoring, health surveillance includes biological effect monitoring, medical surveillance, examinations, and inspections and review of records.
Health surveillance should be triggered by the risk assessment process and cover workers exposure to industrial chemicals by all routes including inhalation, ingestion and skin absorption.
Biological Monitoring:
Biological monitoring is the assessment of worker exposure to a hazardous agent through the measurement of a biomarker which results from contact with the agent. The biomarker typically is the agent or its metabolite in a biological specimen derived from the worker; examples are styrene in expired air, styrene in blood, and mandelic and phenylglyoxylic acids (metabolites of styrene) in urine. The biomarker also can be an effect of the agent, such as elevated levels of zinc protoporphyrin in blood, caused by exposure to lead.
Industrial hygiene professionals use biological monitoring to assess the risk to workers from exposure hazards and to demonstrate the adequacy of control technologies and intervention strategies. Biological monitoring has the potential to assess worker exposure to industrial chemicals by all routes, including inhalation, skin absorption, and ingestion.
Monitoring Goals:
Air monitoring (or workplace environmental monitoring) and biological monitoring have complementary goals and frequently are applied simultaneously in industrial hygiene investigations.
1. Air Monitoring:
Air monitoring provides an estimate of the potential for exposure to an agent. The presence of a health hazard is estimated, by reference to environmental exposure limits such as the NIOSH recommended exposure levels, the Occupational Safety and Health Administration (OSHA) permissible exposure levels, or the threshold limit values (TLVsTM) of the American Conference of Governmental Industrial Hygienists (ACGIH).
Compared with biological monitoring, air monitoring offers advantages in certain situations. If the agent has acute toxic effects on the respiratory tract or the eyes, air monitoring is the logical tool for controlling the exposure. Air monitoring can be conducted continuously and, thus, can detect peak exposures to dangerous chemicals.
2. Biological Monitoring of Exposure:
A biomarker of exposure represents uptake of the agent through all routes of exposure. Thus, compared to air monitoring, biological monitoring offers a better estimate of the health risk in situations where routes of exposure other than inhalation are significant.
(a) The rate of disappearance of a biomarker determines the period of time after exposure during which the level of the biomarker is still affected by the exposure. The levels of rapidly disappearing biomarkers primarily reflect exposures during the previous several hours. On the other hand, biomarkers which disappear over the course of several weeks reflect one, several, or numerous exposure incidents occurring anytime during a period of several weeks previous to the measurement.
(b) Some toxicants accumulate in one or several parts of the body and are in dynamic equilibrium with the sites of toxicity. In the case of polychlorinated biphenyl (PCB), which accumulates in fatty tissue, the blood level of PCB reflects the amount stored in the body.
(c) When the site of critical action for a toxicant is known, the concentration of the biomarker at that site can be used as a measure of the biologically effective dose. Carboxyhemoglobin is such a biomarker for carbon monoxide poisoning. In this case, the biomarker level is correlated with the health effect.
Biological Monitoring of Effect:
This term is defined as monitoring reversible biochemical changes resulting from exposures. The degree of change is less than that which leads to injury and is not associated with a known irreversible pathological effect Biological monitoring of effect is not health surveillance through which individuals with early signs of adverse health effects are identified.
Some examples of biomarkers of effect are:
(a) Zinc protoporphyrin in blood, levels of which increase with lead exposure, because lead inhibits the biosynthesis of heme.
(b) Protein and DNA adducts of aromatic amines in blood. These adducts can both reflect the intensity of exposure and be correlated with the biologically effective dose.
(c) Antibodies produced against low-molecular-weight molecules. Some chemicals, while not immunogenic in their own right because of small size and other limitations, may bind to constitutive polymers (such as host proteins) and become immunogenic, causing the production of specific antibodies.
Alternatively, such exposures may lead to production of new antigenic determinants, through non-adduct-forming reactions of the agent with selected protein-carrier molecules. Antibodies can be made to these modified proteins or to the parent hapten-conjugate in both cases; the antibodies may remain in the human system much longer than the toxicant which initiated their development.
Biological Matrices:
The most common matrices used for biological monitoring are exhaled air, blood, and urine.
1. Monitoring exhaled air is limited to volatile chemicals. Exhaled air monitoring is not suitable for chemicals inhaled as aerosols or for gases and vapors, which decompose upon contact with body fluids or tissues, or which are highly soluble in water, such as ketones and alcohols.
2. Blood is the medium which transports chemicals metabolites in the body.
Therefore, most biomarkers present in the body can be found in the blood during some period of time after exposure.
(a) A chemical in the blood is in dynamic equilibrium with various parts of the body: the site of entry, tissues in which the chemical is stored, and organs in which it is metabolized or from which it is excreted. Thus, the concentration of a biomarker in the blood may differ between regions of the circulatory system. This would be the case during pulmonary uptake or elimination of a solvent, which would cause differences in concentration between capillary blood (mainly arterial blood) and venous blood.
(b) Two advantages of blood monitoring are- (1) The gross composition of blood is relatively constant between individuals. This eliminates the need to correct measured biomarker levels for individual differences. (2) Obtaining specimens is straightforward and with proper care can be accomplished with relatively little risk of contamination.
(c) An important consideration in blood monitoring is that obtaining blood specimens requires an invasive procedure and should be performed only by trained persons.
3. Urine is more suitable for monitoring hydrophilic chemicals, metals, and metabolites than for monitoring chemicals poorly soluble in water. The concentration of the biomarker in urine usually is correlated to its mean plasma level during the period the urine dwells in the bladder.
(a) In some instances the urine concentration is affected by the amount of the biomarker stored in the kidneys. Examples are cadmium and chromium.
(b) The accuracy of the exposure estimate, using urine monitoring, depends upon the sampling strategy. The most influential factors are time of collection and urine output.
(c) Measurements from 24-hour specimens are more representative than from spot samples and usually correlate better with intensity of exposure. However, collection, stabilization, and transportation of 24-hour specimens in the field are difficult and often not feasible.
Sources of Bio-monitoring Action Levels:
(a) Biological Exposure Indices (BEI) adopted by the American Conference of Governmental Industrial Hygienists (ACGIH).
(b) Biological Tolerance Values for Working Materials (BAT) published by the Deutsche Forschungsgemeinschaft’s (DFG) Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area.
(c) Lauwerys’ and Hoet’s “Summary of Recommendations” in Industrial Chemical Exposure. Guidelines for Biological Monitoring.
(d) Occupational Safety and Health Administration (OSHA) standards.