Health&Safety_Midterms

• Toxicology is the science that studies the harmful effects of chemicals on living tissue. A toxic (poisonous) substance is one that has a 

  negative effect on the health of a human or animal
• a toxic substance is going to hurt you, if not right away, then at some time in the future
• About every 20 minutes a new and potentially hazardous chemical is introduced into American industry.
• Smoking does not noticeably harm you right away, but 30 years of smoking will definitely show symptoms. This delay is known as latency and is a serious problem in identifying carcinogenic (cancer causing) compounds
• There are numerous government regulations addressing chemical hazards. Some of them, to name just a few, are: 

  • OSHA 29 CFR 1910.1200 Hazard Communication 

  • OSHA 29 CFR 1910.119 Process Safety Management 

  OSHA 29 CFR 1910.120 Hazardous Waste Operations and Emergency Response 

  • EPA Toxic Substance Control Act 

  ⚫ EPA Resource Conservation and Recovery Act 

  • DOT hazardous Materials Handling: Loading and Unloading 
• A substance can be considered toxic (poisonous) when a small quantity will cause in- jurious effects in the body of the average normal adult human. Almost all materials are injurious to living organisms to some extent
•  Exposure is when a chemical, infectious material or other agent enters or is in direct contact with the body
• Contamination occurs when the hazardous material remains on the clothing, hair, skin, or other part of a person.
• Exposure can occur without contamination, but contamination usually results from exposure.
• Certain persons have unusual susceptibilities to substances that produce violent or fatal reactions when absorbed in small amounts harmless to most other persons. Such substances are called allergens, and a person is said to have an allergy or to be allergic to the substance. Allergies have been reported to almost every known common material. 
• In addition to individual susceptibility, other conditions affect the severity of the injury caused by the toxin. These other conditions are the: 

  Size and duration of the dose 

  Route taken into the body 

  • Degree of toxicity 

  • Rate of absorption 

  • Environmental temperature 

  • Physical condition of the affected person 
•  Generally, the greater the toxicity of the substance, the faster the rate of absorption, and the warmer the temperature, the more rapid the occurrence of the injury.
• Toxic agents cause injuries in different ways and have been categorized into seven types (see Figure 5-1): asphyxiates, irritants, systemic poisons, anesthetics, neurotics, corrosives, and carcinogens. 
• Although the term asphyxia is commonly thought to mean suffocation, it actually means hypoxia (lack of oxygen) and the presence of high carbon dioxide levels in the blood. Asphyxiates can be either "simple" or "chemical." Simple asphyxiates are generally con- sidered to be those gases which dilute breathable air to such an extent that the blood re- ceives an inadequate supply of oxygen. In other words, you are in an oxygen deficient atmosphere. 
• Some common asphyxiates are carbon dioxide and nitrogen. They are especially insidi- ous because they are odorless and colorless. Hydrogen and helium are rarely asphyxiates because both are lighter than air and diffuse rapidly in the open. They tend to leak away rather than collect and displace air in an area. Nitrogen at room temperatures is slightly lighter than air, but at low temperatures, such as during leakage from tanks containing cryogenic nitrogen or where rapid expansion cools the gas, nitrogen becomes heavier than 
• Chemical asphyxiates are toxic agents which enter into reactions to cause histotoxic hypoxia. These chemicals prevent the red blood cells from carrying oxygen. Some more familiar chemical asphyxiates are carbon monoxide, nitrites, hydrogen sulfide, and aniline. 
• An irritant can be a gas, liquid, or fine particulate matter. Ammonia is a familiar and common irritant. Irritants injure the body by inflaming the tissues at the point of contact. Heat, redness, swelling, and pain are signs of inflammation. Mild irritants cause the capillaries to dilate and fill with blood, causing the redness and increased heat. The permeability of the capillary walls change, and fluid passes from the blood into the spaces between the tissues and causes swelling and pain. Strong irritants can produce blisters.
• Black lung disease from coal dust 

  Silicosis from fine rock dust 

  Asbestosis and cancer from asbestos fibers 

  • Emphysema from cigarette smoke 
• A sensitizer may not cause injury immediately, but will produce susceptibility to a second attack or to other substances. Where sensitivity or allergy dermatitis exists and the skin is affected even by small amounts of the chemical, the affected worker should not be allowed in areas where the chemical is used. 
• Dermatitis is an inflammation caused by defatting of the skin or by contact with an irritating or sensitizing substance. Exposure to solvents often removes oils that keep the skin soft and pliable. Without the oil, the skin is dry, scaly, and tends to crack easily. Such skin has poor resistance to bacterial infections and heals slowly when injured.
• Systemic poisons cause injury after they have been carried to the tissues of the body, es- pecially to specific organs (target organs). Some systemics cause histotoxic hypoxia by interfering with the use of oxygen and others interfere with reactions necessary for the organs to continue their normal functions. For example, some toxic agents shut down the kidneys. The most damaging effects of systemic poisons occur at the kidneys, lungs, liver, and gastrointestinal tract.
• Systemic poisons can be divided into the following four categories: 

  1. Chemicals that cause injury to one or more of the visceral organs such as the kidneys or liver. The majority of the halogenated hydrocarbons belong in this group. 

  2. Chemicals that injure the bone marrow, spleen, and the blood-forming system 

  and cause anemia and reduced count of white blood corpuscles.
• metabolic changes to the chemical in the body create toxic products more injurious than the toxin originally absorbed. Because time is required for some substances to change within the body to other compounds, serious symptoms may not occur for several days after initial ingestion. 
•  For instance, the toxins that affect the liver are called hepatotoxins, those affecting the kidneys are called nephro- toxins, those affecting the nervous system are called neurotoxins, and those affecting bone marrow and the blood system are called hemotoxins. 
• Carbon tetrachloride, trichloroethylene, and polyvinyl chloride (PVC) are well known he- patotoxins. Nephrotoxins are the chemicals that affect the kidneys. Since a large amount of blood circulates through the kidneys, they are susceptible to chemical attack if the blood contains a toxin
• Heavy metals, chlorinated and fluorinated hydrocarbons, carbon disulfide, and ethylene glycol are some examples of kidney poisons. Many of these toxins can enter the body through inhalation or absorption. Toxins can be detected through medical surveillance, which monitors metabolites in the urine. Metabolites are the products formed by the toxin after it undergoes changes due to metabolism.
• Reproductive toxins pose a danger to both male and female workers. They can cause gene mutations and affect the reproductive system by affecting sperm count in males or fertility in females. Teratogens are chemicals that affect the offspring. Polychlorinated biphenyls (PCBs), cadmium, and methyl mercury are known reproductive teratotoxins. 
• Anesthetics cause the loss of sensation in the body. The loss of sensation can be general or local. Anesthetics cause respiratory failure by depressing the nervous system and interfering with involuntary muscular action. Some halogenated hydrocarbons generally used as cleaning or degreasing agents can produce this effect. Familiar compounds that have an anesthetic effect are ethyl ether, chloroform, and nitrous oxide.
• A depressant is an agent that reduces functional activity and vital energies. Depressants may exhilarate for a short period of time and then cause the person to become drowsy and lethargic. Breathing may be labored and there may be a loss of consciousness.
• Neurotics affect the nervous system, brain, or spinal cord and may be either depressants or stimulants. Ethyl alcohol and drugs are examples of neurotic agents that cause exhilaration and then deep depression. 
• It can be selective and act on specific organs, such as the brain, while other organs are little affected. Drugs such as marijuana, cocaine, hashish, LSD, and others have adverse effects on the body (and safety). The effect of each depends on the type of drug, dosage, time since taken, susceptibility, and other factors. 
• In extreme cases, the affected person may have a rapid pulse, jerking of the muscles, disorganized vision, and sometimes delirium. Caffeine, found in small amounts in coffee, stimulates the brain and nervous system. Stimulants taken to overcome fatigue wear off and the body succumbs to fatigue, perhaps at the wrong time, which could result in an accident. Because of scenarios like this, drugs are unacceptable in the workplace. They are responsible for erratic employee behavior. 
• Carcinogens - Certain chemicals cause cancer of the internal organs and systems of the body. Tar, bitumen, anthracene, and their compounds, products, and residues can cause cancers of the skin.
• Corrosives damage by chemical destruction of the tissue they contact. Strong acids (hy- drochloric, nitric and sulfuric) or alkalis (sodium hydroxide and potassium hydroxide) can cause corrosive burns.
• Alkalis can cause progressive burns, meaning the injury increases as the alkali moves through the damaged tissue. This is especially critical in injuries to the eye, where delicate tissues can be damaged little by little until vision is destroyed.
• A toxin may enter the body in many different ways but the four major routes are: 

  • Inhalation 

  • Ingestion 

  • Absorption 

  • Injection 
• Occupational Safety and Health Administration (OSHA) places high importance on this route because inhaled toxins reach body organs very fast and rapidly cause adverse effects.
• This route of exposure gives little time to administer corrective action. Inhalation sends the toxin to the blood stream and since the blood stream serves all the cells in the body, the toxin reaches all the cells. In many cases, the inhalation effects can be wide spread, affecting lungs, kidneys, bones, bone marrow, spleen, etc.
• Carbon dioxide, a simple asphyxiant, which dilutes oxygen and produces an hypoxic condition in the blood that starves the body cells of oxygen. Absorbed hexane vapors attack the peripheral nervous system and can cause peripheral neuropathy.
• Many heavy metal ions, such as chromium or nickel, may damage the kidneys and are called nephrotoxins. They can be inhaled as a fine dust or mist. Though they damage the kidneys, their effect on other body organs may be minimal.