8 Health Hazards 8.1 OCCUPATIONAL ILLNESSES Occupation illnesses are not as easily identified as injuries. According to the Bureau of Labor Statistics, there were 5.7 million injuries and illnesses reported in 1999. Of this number only 372,000 cases of occupational illnesses were reported. The 372,000 occupational illnesses included repeat trauma such as carpal tunnel syndrome, noise- induced hearing loss, and poisonings. It certainly appears that many occupational illnesses go unreported when the employer or worker is not able to link exposure with the symptoms the employees are exhibiting. Also, physicians fail to ask the right questions regarding the patients employment history, which can lead to the com- monest of diagno ses of a cold or flu. This has become very apparent with the recent occupational exposure to anthrax where a physician sent a worker home with anthrax without addressing his=her potential occupational exposure hazards. Unless Exposure in the workplace can cause occupationally related illnesses. (Courtesy of the U.S. Environmental Protection Agency.) ß 2008 by Taylor & Francis Group, LLC. physicians are trained in occupational medicine, they seldom address work as the potential exposure source. This is not entirely a physician problem by any means since the symptoms that are seen by the physician are often those of flu and other common illnesses suffered by the general public. It is often up to the employee to make the physician aware of their on- the-job exposure. If, I have continuously used the term exposure since, unlike trauma injuries and deaths, which are usually caused by the release of some source of energy, occupational illnesses are often due to both short- and long-term exposures. If the result of an exposure leads to immediate symptoms, it is said to be acute. If the symptoms come at a later time, it is termed a chronic exposure. The time between exposure and the onset of symptoms is called the latency period. It could be days, weeks, months, or even years, as in the case of asbestos where asbestosis or lung cancer appears 20–30 years after exposure. It is often very difficult to get employers, supervisors, and employees to take seriously the exposur es in the workplace as a potential risk to the workforce both short and long term, especially long term. ‘‘It cannot be too bad if I feel alright now.’’ This false sense of security is that the workplace seems safe enough. The question is how bad could it be in our workplace? Everyone seems well enough now. 8.2 IDENTIFYING HEALTH HAZARDS Health-related hazards must be identified (recognized), evaluated, and controlled to prevent occupational illnesses, which come from exposure to them. Health-related hazards come in a variety of forms, such as chemical, physical, ergonomic, or biological: . Chemical hazards arise from excessive airbo rne concentrations of mists, vapors, gases, or solids that are in the form of dusts or fumes. In addition to the hazard of inhalation, many of these materials may act as skin irritants or may be toxi c by absorption through the skin. Chemicals can also be ingested although this is not usually the principle route of entry into the body. . Physical hazards include excessive levels of nonionizing and ionizing radiations, noise, vibration, and extremes of temperature and pressure. . Ergonomic hazards include improperly designed tools or work areas. Improper lifting or reaching, poor visual conditions, or repeated motions in an awkward position can result in accidents or illnesses in the occupa- tional environment. Designing the tools and the job to be done to fit the worker should be of prime importance. Intelligent application of engin- eering and biomechanical principles is required to eliminate hazards of this kind. . Biological hazards include insects, molds, fungi, viruses, vermin (birds, rats, mice, etc.), and bacterial contaminants (sanitation and house- keeping items such as potable water, removal of industrial waste and sewage, food handling, and personal cleanliness can contribute to the effects from biological hazards). Biological and chemical hazards can overlap. ß 2008 by Taylor & Francis Group, LLC. Health-rela ted hazards can often be elusive and difficult to identify. A common example of this is a contamina nt in a building that has caused symptom s of illness . Even the ev aluation process may not be able to detect the contam inant that has dissipated before a samp le can be coll ected. This leaves nothi ng to contr ol and possibly no an swer to what caused the ill nesses. Table 8.1 depicts the most common reported illness es in the wor kplace. 8.3 HEALTH HAZARDS Health hazards are caused by any chemi cal or biol ogical exposur e that inte racts adversely with organs wi thin our body causi ng illn esses or injuries . The maj ority of chemical expo sures result from inhal ing chemi cal contam inants in the form of vapors, gases, dusts , fume s, and mis ts, or by skin ab sorption of these mat erials. The degree of the hazard depends on the lengt h of exposur e time and the amoun t or quantity of the chemi cal agen t. This is co nsidered to be the dose of a substanc e. A chemical is consi dered a poiso n when it causes harmful effects or inte rferes with biological react ions in the body. Only those chemi cals that are associated wi th a great risk of harmful effects are desig nated a s poiso ns (Figur e 8.1). Dose is the most importan t factor deter mining whether or not you will have an adverse effect from a chemi cal exposur e. The longer you wor k at a job and the more chemical agent that gets into the air or on you r skin, the higher the dose potent ial. Two compo nents that make up dose are as follow s: 1. The length of exposur e, or how long you are exposed — 1 h, 1 day, 1 year, 10 years, etc 2. The quanti ty of substance in the air (concen tration) , how much you get on your skin, and=or the amoun t e aten or ingested Another importan t facto r to consider about the dose is the relat ionship of tw o or more chemicals acting together that cause an increased risk to the bo dy. This interaction of chemicals that multip ly the chance of harm ful effects is call ed a TABLE 8.1 Repor ted Non fatal Occupat ional Illnesses Type of Illness Total Illnesses Reported (%) Skin disease or disorders 17 Respiratory conditions because of toxic agents 8 Poisoning 1 Hearing loss 11 All other diseases 62 Source: From Bureau of Labor Statistics. United States Department of Labor. Workplace Injuries and Illnesses in 2004. Available at http:==bls.gov. ß 2008 by Taylor & Francis Group, LLC. synergistic effect. Many chemicals can interact and although the dose of any one chemical may be too low to affect you, the combination of doses from different chemicals may be harmful. For example, the combination of chemical exposures and a personal habit such as cigarette smoking may be more harmful than just an exposure to one chemical. Smoking and exposure to asbestos increase the chance of lung cancer by as much as 50 times. The type and severity of the body’s response is related to dose and the nature of specific contaminant present. Air that looks dirty or has an offensive odor may, in fact, pose no threat whatsoever to the tissues of the respiratory system. In contrast, some gases that are odorless or at least not offensive can cause severe tissue damage. Particles that normally cause lung damage cannot even be seen. Many times, however, large visible clouds of dust are a good indicator that smaller particles may also be present. The body is a complicated collection of cells, tissues, and organs having special ways of protecting itself against harm. We call these the body’s defense systems. The body’s defense system can be broken down, overcome, or bypassed. This can result in injury or illness. Sometimes, job-related injuries or illnesses are temporary, and you can recover completely. At other times, as in the case of chronic lung diseases like silicosis or cancer, these are permanent changes that may lead to death. FIGURE 8.1 Chemical exposure poses real health issues for workers. (Courtesy of the U.S. Environmental Protection Agency.) ß 2008 by Taylor & Francis Group, LLC. 8.3.1 ACUTE HEALTH EFFECTS Chemicals can cause acute (short-term) or chronic (long-term) effects. Whether or not a chemical causes an acute or chronic reaction depends both on the chemical and the dose you are exposed to. Acute effects are seen quickly, usually after exposures to high concentrations of a hazardous material. For example, the dry cleaning solvent perchloroethylene can immediately cause dizziness, nausea, and at higher levels, coma and death. Most acute effects are temporary and reverse shortly after being removed from the exposure. But at high enough exposures permanent damage may occur. For most substances, neither the presence nor absence of acute effects can be used to predict whether chronic effects will occur. Dose is the determining factor. Exposures to cancer-causing substances (carcinogens) and sensitizers may lead to both acute and chronic effects. An acute exposure may occur, for example, when we are exposed to ammonia while using another cleaning agent. Acute exposure may have both immediate and delayed effects on the body. Nitrogen dioxide poisoning can be followed by signs of brain impairment (such as confusion, lack of coordination, and behavioral changes), days or weeks after recovery. Chemicals can cause acute effects on breathing. Some chemicals irritate the lungs and some sensitize the lungs. Fluorides, sulfides, and chlorides are all found in various welding and soldering fluxes. During welding and soldering, these materials combine with the moisture in the air to form hydrofluoric, sulfuric, and hydrochloric acids. All three can severely burn the skin, eyes, and respiratory tract. High levels can overwhelm the lungs, burning and blistering them, and causing pulmonary edema. (Fluid building up in the lungs will cause shortness of breath and if severe enough can cause death.) In addition, chemicals can have acute effects on the brain. When inhaled, solvent vapors enter the bloodstream and travel to other parts of the body, particularly the nervous system. Most solvents have a narcot ic effect. This means they affect the nervous system by causing dizziness, headaches, inebriation, and tiredness. One result of these symptoms may be poor coordination, which can contribute to falls and other accidents on a worksite. Exposure to some solvents may increase the effects of alcoholic beverages. 8.3.2 CHRONIC HEALTH EFFECTS A chronic exposure occurs during longer and=or repeated periods of contact, some- times over years and often at relatively low concentrations of exposure. Perchloro- ethylene or alcoho l, for example, may cause liver damage or other cancers 10–40 years after first exposure. This period between first exposure and the development of the disease is called the latency period. An exposure to a substance may cause adverse health effects many years from now with little or no effects at the time of exposure. It is important to avoid or eliminate all exposures to chemicals that are not part of normal ambient breathing air. For many chemical agents, the toxic effects following a single exposure are quite different from those produced by repeated exposures. For example, the primary acute toxic effect of benzene is central nervous system damage, while chronic exposures can result in leukemia. ß 2008 by Taylor & Francis Group, LLC. There are two ways to determine if a chemical causes cancer: studies conducted on people and studies on animals. Studies on humans are expensive, difficult, and near impossible. This type of long-term research is called epidemiology. Studies on animals are less expensive and easier to carry out. This type of research is sometimes referred to as toxicology. Results showing increased occurrences of cancer in animals are generally accepted to indicate that the same chemical causes cancer in humans. The alternative to not accepting animal studies means we would have a lot less knowledge about the health effects of chemicals. We would never be able to determine the health effects of the more than 100,000 chemicals used by the industry. There is no level of exposure to cancer-causing chemicals that is safe. Lower levels are considered safer. One procedure for setting health standard limits is called risk assessment. Risk assessment on the surface appears very scientific yet the actual results are based on many assumptions. It is differences in these assumptions that allow scientists to come up with very different results when determining an acceptable exposure standard. The following are major questions that assumptions are based on: . Is there a level of exposure below which a substance would not cause cancer or other chronic diseases? (Is there a threshold level?) . Can the body’s defense mechanisms inactivate or break down chemicals? . Does the chemical need to be at a high enough level to cause damage to a body organ before it will cause cancer? . How much cancer should we allow? (One case of cancer among 1 million people, or one case of cancer among 100,000 people, or one case of cancer among 10 people?) For exposures at the current permissible exposure limit (PEL), the risk of deve- loping cancer from vinyl chloride is about 700 cases of cancer for each million workers exposed. The risk for asbestos is about 6,400 cases of cancer for each million workers exposed. The risk for coal tar pitch is about 13,000 cases for each million workers exposed. PELs set for current federal standards differ because of these different risks. The dose of a chemical-causing cancer in human or animal studies is then used to set a standard PEL below which only a certain number of people will develop illness or cancer. This standard is not an absolute safe level of exposure to cancer-causing agents, so exposure should always be minimized even when levels of exposure are below the standard. Just as the asbestos standard has been lowered in the past from 5 to 0.2 fibers=cm 3 , and now to 0.1 fibers=cm 3 (50 times lower). It is possible that other standards will be lowered in the future as new technology for analysis is discovered and public outrage insists on fewer deaths for a particular type of exposure. If a chemical is suspected of causing cancer, it is best to minimize exposure, even if the exposure is below accepted levels. 8.3.3 CHRONIC DISEASE Chronic disease is not always cancer. There are many other types of chronic diseases, which can be as serious as cancer. These chronic diseases affect the function of ß 2008 by Taylor & Francis Group, LLC. different organs of the body. For example, chronic exposur e to asbestos or silica dust (fine sand) causes scarring of the lung. Exposure to gases such as nitrogen oxides or ozone may lead to destruction of parts of the lung. No matter what the cause, chronic disease of the lungs will make the individual feel short of breath and limit their activity. Depending on the extent of disease, chronic lung disease can kill. In fact, it is one of the top 10 causes of death in the United States. Scarring of the liver (cirrhosis) is another example of chronic disease. It is also one of the 10 causes of death in the United States. The liver is important in making certain essential substances in the body and cleaning certain waste products. Chronic liver disease can cause fatigue, wasting away of muscles, and swelling of stomach from fluid accumulation. Many chemicals such as carbon tetrachloride, chloroform, and alcohol can cause cirrhosis of the liver. The brain is also affected by chronic exposure. Chemicals such as lead can decrease IQ and memory, and=or increase irritability. Many times these changes are small and can only be found with special medi cal tests. Workers exposed to solve nts, such as toluene or xylene in oil-based paints, may develo p neurological changes over a period of time. Scarring of the kidney is another examp le of a chronic disease. Individuals with severe scarring must be placed on dialysis to remove the harmful waste products or have a kidney transplant. Chronic kidney disease can cause fatigue, high blood pressure and swollen feet, as well as many other symptoms. Lead, mercury, and solvents are suspect causes of chronic kidney disease. 8.3.4 BIRTH DEFECTS=INFERTILITY The ability to have a healthy child can be affected by chemicals in many different ways. A woman may be unable to conceive because a man is infertile. The production of sperm may be abnormal, reduced, or stopped by chemicals that enter the body. Men working in an insecticide plant manufacturing 1,3-di bromo-3-chloropropane (DBCP) realized after talking among themselves that none of their wives had been able to become pregnant. When tested, all the men were found to be sterile. A woman may be unable to conceive or may have frequent early miscarriages because of mutagenic or embryotoxic effects. Changes in genes in the woman’s ovaries or man’s sperm from exposure to chemicals may cause the developing embryo to die. A woman may give birth to a child with a birth defect because of a chemical with mutagenic or teratogeni c effects. When a chemical causes a terato- genic effect, the damage is caused by the woman’s direct exposure to the chemical. When a chemical causes a mutagenic effect, changes in genes from either the man or woman have occurred. Many chemicals used in the workplace can damage the body. Effects range from skin irritation and dermatitis to chronic lung diseases such as silicosis and asbestosis or even cancer. The body may be harm ed at the point where a chemical touches or enters it. This is called a local effect. When the solvent benzene touches the skin, it can cause drying and irritation (local effect). A systemic effect develops at some place other than the point of contact. Benzene can be absorbed through the skin, breathed into the lungs, or ingested. ß 2008 by Taylor & Francis Group, LLC. Once in the body, benzene can affect the bone marrow, leading to anemia and leukemia. (Leukemia is a kind of cancer affecting the bone marrow and blood.) Adverse health effects may take years to develop from a small exposure or may occur very quickly to large concentrations. 8.4 BIOLOGICAL MONITORING Biological monitoring is the analysis of body systems such as blood, urine, finger- nails, teeth, etc. that provide a baseline level of contaminants in the body. Medical testing can have several different purposes, depending on why the worker is visiting a doctor. If it is a preemployment examination, it is usually considered a baseline to use as a reference for future medical testing. Baselines are a valuable tool to measure the amount of toxic substances in the body and often give an indication of the effectiveness of personal protective equipment (PPE) (Figure 8.2). Occupational Safety and Heal th Administration (OSHA) regulations allow the examining physician to determine most of the content reviewed in the examination. Benefits received from an examination will vary with content of the examination. No matter what tests are included in the examination, there are certain important limitations of medical testing: . Medical testing cannot prevent cancer. Cancer from exposure to chemicals or asbestos can only be prevented by reducing or eliminating an exposure. . For many conditions, there are no medical tests for early diagnosis. For example, the routine blood tests conducted by doctors for kidney functions do not become abnormal until half the kidney funct ion is lost. Nine of ten FIGURE 8.2 Biological monitoring is a part of medical assessment. (Courtesy of the U.S. Environmental Protection Agency.) ß 2008 by Taylor & Francis Group, LLC. people with lung cancer die withi n 5 years because chest x-rays do no t diagnose lung cancer in time to save the indi vidual. . No medical test is perfect . So me tests are falsely abnormal and some false ly normal. 8.4.1 MEDICAL QUESTIONNAIRE A medical and work history, despi te comm on percept ions, is probably the most importan t part of an examinati on. Most diagno ses of disea se in medi cine are made by the work history. Labo ratory tests are used to con firm past illness es and inju ries. Doctors are inte rested in the history of lung, heart , kidney , liver, and other chroni c diseases for the indi vidual and family. The doctor will also be concern ed about symptom s indi cating heart or lung disea se and smok ing habits. A physic al examinati on is very bene ficial for routi ne screen ing. Good results are importan t but an indi vidual may be physi cally fit and still have a serious medical problem. Blood is test ed for blood cell production (anemia), liver function, kidney function, and if taken while fast ing, for increased sugar, choles terol, an d fat in the blood. Urine is tested for kidney funct ion and diabet es (sugar in the urine). It is possible to meas ure in the blood and urine c hemicals that get into the body from exposures on a jobsite. This type of testing is call ed biol ogical monitor ing. 8.4.2 P ULMONARY FUNCTION T ESTS A spiro meter measures the volume of air in an indi vidual ’ s lungs and how quickly he=she can breathe in and out. This is called pulmonary funct ion testing. This is useful for diagnosing disea ses that cause scarr ing of the lungs that affect s the expandab ility (asbes tosis). Emphys ema or asthma may also be diagno sed with pulmonary funct ion testing. It is vital for ev aluating the abil ity of an individua l to wear a respirato r without additional healt h risk . 8.4.3 ELECTROCARDIOGRAM An elect rocard iogram is a test used to meas ure heart injury or irre gular heart be ats. Work can be extremely strenuous, particularly when wearing protective equipment in hot environments. A stress test utilizing an electrocardiogram while exercising is sometimes a help in determining fitness, especially if there are indications from the questionnai re that a n indi vidual has a high risk of heart disea se (Figur e 8.3). 8.4.4 CHEST X-RAY X-rays are useful in determining the cause of breathing problems or to use as a baseline to determine future problems. A chest x-ray is used to screen for scarring of the lungs from exposure to asbestos or silica. It should not be performed routinely, unless the history indicates a potential lung or heart problem and the physician thinks a chest x-ray is necessary. Some OSHA regulations require chest x-rays as part of the medical surveillance progra m. Unnecessary x-ray screening should be eliminated. For work-related biological monitoring, it is suffi cient to have chest x-rays every 5 years. ß 2008 by Taylor & Francis Group, LLC. 8.5 HAZARDOUS CHEMICALS Hazardous and toxic (poisonous) substances can be defined as harmful chemicals present in the workplace. In this definition, the term ‘‘chemicals’’ include s dusts, mixtures, and common materials such as paints, fuels , and solvents. OSHA currently regulates exposure to approximately 400 substances. The OSHA chemical sampling information file contai ns a listing for approximately 1500 substances. The Environ- mental Protection Agency’s (EPA) Toxic Substance Chemical Act Chemical Sub- stances Inventory lists information on more than 62,000 chemicals or chemical substances. Some libraries maintain files of material safety data sheets (MSDSs) for more than 100,000 substances. It is not possible to address the hazards associated with each of these chemicals. Since there is no evaluation instrument that can identify the chemical or the amount of chemical contaminant present, it is not possible to be able to make a real- time assessment of a worker’s exposure to potentially hazardous chemicals. Addi- tionally, threshold limit values (TLVs) provided by the American Conference of Governmental Industrial Hygienist (ACGIH) in 1968 are the basis of OSHA ’s PELs. In the early 2000s, workers are being provided protection with chemical exposure standards that are 40 years old. The ACGIH regularly updates and changes its TLVs based upon new scientific information and research. The U.S. EPA allows for one death or one cancer case per million people exposed to a hazardous chemical. Certainly, the public needs these kinds of protec- tions. Using the existing OSHA PELs, risk factor is only as protective as one death because of exposure in 1000 workers. This indicates that there exists a fence line mentality which suggests that workers can tolerate higher exposures than what the public would be subjected to. As one illustration of this, the exposure to sulfur FIGURE 8.3 Work is often a strain on the heart. (Courtesy of the U.S. Environmental Protection Agency.) ß 2008 by Taylor & Francis Group, LLC. [...]... 92933 2 a-Naphthylamine, CAS No 134327 3 Methyl chloromethyl ether, CAS No 107302 4 3,30 -Dichlorobenzidine (and its salts), CAS No 91941 5 Bis-chloromethyl ether, CAS No 54 288 1 6 b-Naphthylamine, CAS No 915 98 7 Benzidine, CAS No 9 287 5 8 4-Aminodiphenyl, CAS No 92671 9 Ethyleneimine, CAS No 151564 10 b-Propiolactone, CAS No 575 78 11 2-Acetylaminofluorene, CAS No 53963 12 4-Dimethylaminoazo-benzene,... than 0.1% by weight or volume of 4-nitrobiphenyl, methyl chloromethyl ether, bis-chloromethyl ether, b-naphthylamine, benzidine, or 4-aminodiphenyl and solid or liquid mixtures containing less than 1.0% by weight or volume of a-naphthylamine, 3,30 -dichlorobenzidine (and its salts), ethyleneimine, b-propiolactone, 2-acetylaminofluorene, 4-dimethylaminoazo-benzene, or N-nitrosodimethylamine The specific... adverse health effects 8. 9 TEMPERATURE EXTREMES 8. 9.1 COLD STRESS Temperature is measured in degrees Fahrenheit (8F) or Celsius (8C) Most people feel comfortable when the air temperature ranges from 668F to 798F and the relative humidity is about 45% Under these circumstances, heat production inside the body equals the heat loss from the body, and the internal body temperature is kept ß 20 08 by Taylor... 117 dBA; and needle guns, up to 112 dBA Exposure to 115 dBA is permitted for a maximum of 15 min for an 8 h workday No exposure above 115 dBA is permitted Traditional dosimetry measurement may substantially underestimate noise exposure levels for construction workers since short-term peak exposures may be responsible for acute and chronic effects Hearing can be lost in lower, full-shift time-weighted... (1910.1017) Inorganic arsenic (1910.10 18) Cadmium (1910.1027 and 1926.1127) Benzene (1910.10 28) Coke oven emissions (1910.1029) 1,2-Dibromo-3-chloropropane (1910.1044) Acrylonitrile (1910.1045) Ethylene oxide (1910.1047) Formaldehyde (1910.10 48) Methylenedianiline (1910.1050) 1,3-Butadiene (1910.1051) Methylene chloride (1910.1052) Recently, OSHA has reduced the PEL for methylene chloride from 400 to 25... syndrome Its most common symptoms are intermittent numbness and tingling in the fingers; skin that turns pale, ashen, and cold; and eventual loss of sensation and control in the fingers and hands Raynaud’s syndrome occurs due to the use of vibrating hand tools such as palm sanders, planners, jackhammers, grinders, and buffers When such tools are required for a job, an assessment should be made to determine... temperature resulting in damage such as frostbite, and by shivering, which increases the body’s heat production This provides a temporary tolerance for cold but cannot be maintained for long periods Overexposure to cold causes discomfort and a variety of health problems Cold stress impairs performance of both manual and complex mental tasks Sensitivity and dexterity of fingers lessen in cold At still lower... industry standard includes only a general minimum requirement for hearing conservation and lacks the specific requirements for an effective hearing conservation program included in the general industry standard (20 CFR 1926.52) NIOSH and the ACGIH have also recommended exposure limits (NIOSH: 85 dBA TWA, 115 dBA ceiling; ACGIH: 85 dBA) Noise, or unwanted sound, is one of the most pervasive occupational health. .. should be considered to help reduce the potential for a vibration-induced CTD The damage caused by vibrating tools can be reduced by ß 20 08 by Taylor & Francis Group, LLC FIGURE 8. 6 The use of anti-vibration gloves Using vibration dampening gloves (Figure 8. 6) Purchasing low vibration tools and equipment Putting anti-vibration material on handles of existing tools Reducing length of exposure... posed to their workforce by the chemicals that they use Employers need to ß 20 08 by Taylor & Francis Group, LLC get and review the MSDSs for all chemicals in use on their worksite and take proper precautions recommended by the MSDSs Also, it behooves workers to get copies of MSDSs for chemicals they use Examples of MSDSs can be found in Appendix B MSDSs can also provide information for training employees . 91941 5. Bis-chloromethyl ether, CAS No. 54 288 1 6. b-Naphthylamine, CAS No. 915 98 7. Benzidine, CAS No. 9 287 5 8. 4-Aminodiphenyl, CAS No. 92671 9. Ethyleneimine, CAS No. 151564 10. b-Propiolactone,. vermin (birds, rats, mice, etc.), and bacterial contaminants (sanitation and house- keeping items such as potable water, removal of industrial waste and sewage, food handling, and personal cleanliness. now. 8. 2 IDENTIFYING HEALTH HAZARDS Health- related hazards must be identified (recognized), evaluated, and controlled to prevent occupational illnesses, which come from exposure to them. Health- related hazards