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| Occupational hazards |
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| Hierarchy of hazard controls |
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Chemical hazards arehazards present inhazardous chemicals and hazardous materials. Exposure to certain chemicals can causeacute or long-term adverse health effects. Chemical hazards are usually classified separately frombiological hazards (biohazards). Chemical hazards are classified into groups that includeasphyxiants,corrosives,irritants,sensitizers,carcinogens,mutagens,teratogens,reactants, andflammables.[1] In the workplace, exposure to chemical hazards is a type ofoccupational hazard. The use ofpersonal protective equipment may substantially reduce the risk of adverse health effects from contact with hazardous materials.[2]
Long-term exposure to chemical hazards such assilica dust,engine exhausts,tobacco smoke, andlead (among others) have been shown to increase risk ofheart disease,stroke, andhigh blood pressure.[3]
| Hazard | Example |
|---|---|
| Flammable and combustible liquids | Diesel |
| Compressed gases | Propane |
| Explosives | TNT |
| Organic peroxides | Methyl ethyl ketone peroxide (used in the manufacturing of polyester) |
| Reactives | Benzoyl peroxide (used as a bleaching agent) |
| Oxidizers | Potassium permanganate (used as an industrial disinfectant and sterilizer) |
| Pyrophorics | White phosphorus |
| Carcinogens | Benzene (feed-stock for many petrochemical processes) |
| Reproductive toxins | Lead,dioxins |
| Teratogens | Thalidomide (immunomodulatory drug) |
| Irritants | Hydrochloric acid (used in food manufacturing and ore processing) |
| Corrosives | Sulfuric acid (used to manufacture chemicals) |
| Sensitizers | Latex |
| Hepatotoxins | Trichloroethylene (used in metal degreasing and dry-cleaning, historically in anaesthesia) |
| Nephrotoxins | Naproxen (anNSAID) |
| Radioactive materials | Uranium salts,plutonium |
The most common exposure route to chemicals in the work environment is throughinhalation.[4] Gas,vapour, mist, dust, fumes, andsmoke can all be inhaled. Those with occupations involving physical work may inhale higher levels of chemicals if working in an area with contaminated air. This is because workers who do physical work will exchange over 10,000 litres of air over an 8-hour day, while workers who do not do physical work will exchange only 2,800 litres.[5] If the air is contaminated in the workplace, more air exchange will lead to the inhalation of higher amounts of chemicals.[6]
Chemicals may be ingested when food or drink is contaminated by unwashed hands or from clothing or poor handling practices.[7] When ingestion of a chemical hazard occurs it comes from when those said chemicals are absorbed while in the digestive tract of the body.Ingestion only occurs when food or drink has contact with the toxicchemical. This can happen through direct or indirect ingestion. When food or drink is brought into an environment where harmful chemicals are unsealed there is the possibility of those chemical vapors or particles contaminating the food or the drink. A more direct form of chemical ingestion is the possibility of consuming the chemical directly. This rarely happens but, it is possible, that if there is little to no labeling on the chemical containers and if they are not secured properly an accident can occur which could lead to someone mistakenly assuming the chemical was something it was not.[8]
Chemical exposure to the skin is a common workplace injury and may also occur in domestic situations with chemicals such as bleach or drain-cleaners. The exposure of chemicals to the skin most often results in local irritation to the exposed area.[9] In some exposures, the chemical will be absorbed through the skin and will result in poisoning.[9] The eyes have a strong sensitivity to chemicals, and are consequently an area of high concern for chemical exposure. Chemical exposure to the eyes results in irritation and may result in burns and vision loss.[10]
Injection is an uncommon method of chemical exposure in the workplace. Chemicals can be injected into the skin when a worker is punctured by a sharp object, such as a needle. Chemical exposure through injection may result in the chemical entering directly into the bloodstream.[11]
Hazard pictograms are a type of labeling system that alerts people at a glance that there are hazardous chemicals present. The symbols help identify whether the chemicals that are going to be in use may potentially cause physical harm, or harm to the environment. The 9 symbols are:[12]
These pictographs are also subdivided into class and categories for each classification.[13] The assignments for each chemical depends on their type and their severity. The standard set of 9 hazard pictograms was published and distributed as a regulatory requirement through the efforts of theUnited Nations via theGlobally Harmonized System of Classification and Labelling of Chemicals.[14]
Chemical exposure is estimated to have caused approximately 190,000 illnesses and 50,000 deaths of workers annually.[15] There exists an unknown link between chemical exposure and subsequent illness or death. Therefore, the majority of these illnesses and deaths are thought to be caused by a lack of knowledge or awareness concerning the dangers of chemicals. The best method of controlling chemical exposure within the workplace is through theelimination or thesubstitution of all chemicals that are thought or known to cause illness or death.[16]
Although elimination and substitution of harmful chemicals is the best known method for controlling chemical exposure, there are other methods that can be implemented to diminish exposure. The implementation ofengineering controls is an example of another method for controlling chemical exposures. When engineering controls are implemented, there is a physical change made to the work environment that will eliminate or reduce the risk to chemical exposure. An example of engineering controls is the enclosure or isolation of the process that creates the chemical hazard.[16]
If the process that creates the chemical hazard cannot be enclosed or isolated, the next best method is the implementation ofadministrative controls and work practices controls. This is the establishment of administrative and work practices that will reduce the amount of time and how often the workers will be exposed to the chemical hazard. An example of administrative and work practices controls is the establishment of work schedules in which workers have rotating job assignments. This will ensure that all workers have limited exposure to chemical hazards.[16]
Employers should providepersonal protective equipment (PPE) to protect their workers from chemicals used within the workplace. The use of PPE prevents workers from being exposed to chemicals through the routes of exposure—inhalation, absorption through skin or eyes, ingestion, and injection. One example of how PPE usage can prevent chemical exposure concerns respirators. If workers wear respirators, they will prevent the exposure of chemicals through inhalation.[16]
In case of an emergency, it is recommended to understand first aid procedures in order to minimize any damage. Different types of chemicals can cause a variety of damage. Most sources agree that it is best to rinse any contacted skin or eye with water immediately. Currently, there is insufficient evidence of how long the rinsing should be done, as the degree of impacts will vary for substances such as corrosive chemicals.
Transporting the affected person to a health care facility may be important, depending on condition. If the victim needs to be transported before the recommended flush time, then flushing should be done during the transportation process. Some chemical manufacturers may state the specific type of cleansing agent that is recommended.[17]
Acarcinogen (/kɑːrˈsɪnədʒən/) is any agent that promotes the development ofcancer.[18] Carcinogens can includesynthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizingradiation, andbiologic agents such as viruses andbacteria.[19] Most carcinogens act by creating mutations inDNA that disrupt a cell's normal processes for regulating growth, leading to uncontrolled cellular proliferation.[18] This occurs when the cell'sDNA repair processes fail to identify DNA damage allowing the defect to be passed down todaughter cells. The damage accumulates over time. This is typically a multi-step process during which the regulatory mechanisms within the cell are gradually dismantled allowing for uncheckedcellular division.[19]
The specific mechanisms for carcinogenic activity is unique to each agent and cell type. Carcinogens can be broadly categorized, however, as activation-dependent and activation-independent which relate to the agent's ability to engage directly with DNA.[20] Activation-dependent agents are relatively inert in their original form, but are bioactivated in the body intometabolites or intermediaries capable of damaging human DNA.[21] These are also known as "indirect-acting" carcinogens. Examples of activation-dependent carcinogens includepolycyclic aromatic hydrocarbons (PAHs),heterocyclic aromatic amines, andmycotoxins. Activation-independent carcinogens, or "direct-acting" carcinogens, are those that are capable of directly damaging DNA without any modification to their molecular structure. These agents typically includeelectrophilic groups that react readily with the net negative charge of DNA molecules.[20] Examples of activation-independent carcinogens includeultraviolet light,ionizing radiation andalkylating agents.[21]
The time from exposure to a carcinogen to the development of cancer is known as thelatency period. For most solid tumors in humans the latency period is between 10 and 40 years depending on cancer type.[22] For blood cancers, the latency period may be as short as two.[22] Due to prolonged latency periods identification of carcinogens can be challenging.
A number of organizations review and evaluate the cumulative scientific evidence regarding the potential carcinogenicity of specific substances. Foremost among these is theInternational Agency for Research on Cancer (IARC). IARC routinely publishes monographs in which specific substances are evaluated for their potential carcinogenicity to humans and subsequently categorized into one of four groupings: Group 1: Carcinogenic to humans, Group 2A: Probably carcinogenic to humans, Group 2B: Possibly carcinogenic to humans and Group 3: Not classifiable as to its carcinogenicity to humans.[23] Other organizations that evaluate the carcinogenicity of substances include theNational Toxicology Program of theUS Public Health Service,NIOSH, theAmerican Conference of Governmental Industrial Hygienists and others.[24]
There are numerous sources of exposures to carcinogens includingultraviolet radiation from the sun,radon gas[25] emitted in residential basements, environmental contaminants such aschlordecone, cigarette smoke and ingestion of some types of foods such as alcohol andprocessed meats.[26] Occupational exposures represent a major source of carcinogens with an estimated 666,000 annual fatalities worldwide attributable to work related cancers.[27] According toNIOSH, 3-6% of cancers worldwide are due to occupational exposures.[22] Well established occupational carcinogens includevinyl chloride andhemangiosarcoma of the liver,benzene andleukemia,aniline dyes andbladder cancer,asbestos andmesothelioma,polycyclic aromatic hydrocarbons andscrotal cancer among chimney sweeps to name a few.
A 2017 SBU report found evidence that workplace exposure to silica dust,engine exhaust orwelding fumes is associated withheart disease.[3] Associations exist for exposure toarsenic,benzopyrenes,lead,dynamite,carbon disulfide,carbon monoxide,metalworking fluids and occupational exposure totobacco smoke.[3] Working with theelectrolytic production of aluminium, or the production of paper when thesulfate pulping process is used, is associated with heart disease.[3] An association was found between heart disease and exposure to compounds which are no longer permitted in certain work environments, such asphenoxy acids containingTCDD (dioxin) orasbestos.[3]
Workplace exposure to silica dust or asbestos is also associated withpulmonary heart disease. There is evidence that workplace exposure to lead, carbon disulfide, or phenoxy acids containing TCDD, as well as working in an environment where aluminium is being electrolytically produced, are associated with stroke.[3]
Pesticides andcarbon disulfide, amongst many other chemical species have been linked to disruptions ofendocrine balances in the brain andovaries.[28] Any contact with harmful chemicals during the first few months of pregnancy or even after has been connected to somemiscarriages and has affected themenstrual cycle to the point that it has been able to blockovulation. Chemicals inducing health issues duringpregnancy may also affectinfants orfetuses.[29]
