Impact of Toxic chemical
There are many materials used in the workplace that can be hazardous. However, in order for them to affect your health, they must contact the body or be absorbed into the body. When assessing the potential health effects from working with a particular material it is necessary to understand difference between "toxicity" and "hazard". 1. TOXICITY is the ability of a substance to produce an unwanted effect when the chemical has reached a sufficient concentration at a certain site in the body.
The more toxic a material is, the smaller the amount of it necessary to be absorbed before harmful effects are caused. The lower the toxicity, the greater the quantity of it necessary to be absorbed. The toxicity of a chemical is generally measured by experiments on animals (quite often rats). If it is measured in terms of the amounts of material necessary to cause death in 50% of the test animals. These values are called LD50 (lethal dose) or LC50 (lethal concentration), and are usually given in weight of material per kg of body weight or airborne concentration of material per set time period respectively. 2. HAZARD is the probability that this concentration in the body will occur.
Toxicity is an inherent property of the material. A material may be very toxic, but not hazardous, if it is handled properly and is not absorbed into the body. On the other hand, a material may have a very low toxicity, but be very hazardous.
Example:
1. An open container of an acid is much more hazardous than a closed container of the same material. 2. Two liquids may possess the same degree of toxicity but present different degrees of hazard:-
One material may be non-irritating to the eyes and nose and odourless. The other may be irritating to the eyes or respiratory system and possess a pungent odour.
The latter material, because of its warning properties presents a lesser degree of hazard.
In order for toxicants to affect the human system either they must cause damage to external tissues, such as the skin or eyes, or they must be able to enter the body by some mechanism.
Routes of Entry
There are three primary routes of entry into the body: ingestion, skin or eye absorption, and inhalation.
Ingestion:- This means taking a material into the body by mouth (swallowing). Ingestion of toxic materials may occur as a result of eating in a contaminated work area.
Absorption- Substances that contact the eye and the skin may be either absorbed into the body or cause local effects. For the majority of organic compounds, the contribution from skin absorption to the total exposure should not be neglected.
Inhalation- This means taking a material into the body by breathing it in. In the lungs, very tiny blood vessels are in constant contact with the air we breath in. As a result, airborne contaminants can be easily absorbed through this tissue. In the occupational environment, this is generally the most important route of entry.
Health Effects - Chronic vs. Acute
Once a toxic substance has contacted the body it may have either acute (immediate) or chronic (long term) effects.
Example: Spilling acid on your hand will cause immediate harm, i.e. a burn to the skin.
Exposure to asbestos or tobacco smoke may result in lung cancer after as much as twenty years (this is a long term effect).
Exposure - Chronic vs Acute
Exposure can be classified as chronic or acute. In chronic exposures, the dose is delivered at some frequency (daily or weekly usually) over a period of time. In acute exposures, the dose is delivered in a single event and absorption is rapid. Usually, a chronic exposure occurs at low concentration and acute exposure at high concentration.
Some materials may only cause harm if given acutely, not having any effect in the long term. Other materials may not exhibit an effect in the short term, but may cause problems after prolonged exposure.
Physiological Classification of Materials
This classification identifies toxic materials on the basis of biologic action.
Irritants - refers to some sort of aggravation of whatever tissue the material comes in contact with.
e.g. ammonia, nitrogen dioxide.
Asphyxiants - exert their effects through a depletion of oxygen to the tissues
e.g. - simple asphyxiants - carbon dioxide, nitrogen, methane, hydrogen chemical asphyxiants - carbon monoxide, hydrogen cyanide, hydrogen sulphide.
Narcotics or Anaesthetics - the main toxic action is the depressant effect upon the Central Nervous System.
e.g. - many organics, chloroform, xylene.
Systemic Poisons - the main toxic action includes the production of internal damage
e.g. Hepatotoxic agents - toxic effects produce liver damage. eg. carbon tetrachloride.
e.g. Nephrotoxic agents - toxic effects produce kidney damage eg. some halogenated hydrocarbons
Carcinogens - agents/compounds that will induce cancer in humans.
e.g. benzene, arsenic, inorganic salts of chromium, nickel, beryllium.
Mutagens - agents that affect the cells of the exposed people in such a way that it may cause cancer in the exposed individiual or an undesirable mutation to occur in some later generation.
e.g. radiation, variety of chemical agents that alter the genetic message.
Teratogens - Agents or compounds that a pregnant woman takes into her body that generate defects in the fetus
e.g. Thalidomide, possibly steroids
Sensitizers-Agents that may cause allergic or allergic-like responses to occur. After an initial exposure to a substance an individual may become sensitized to that substance. Subsequent exposures to the same substance, often at a much lower concentration than before, produce an allergic response. This response may be a skin rash (dermatitis) or an asthmatic-like attack, depending on the route of exposure.
e.g. cutting oils, isocyanates in polyurethane foam operations and paint spraying operations, some laboratory solvents.
Impact on Environmental
Over the past century humans have introduced a large number of chemical substances into the environment. Some are the waste from industrial and agricultural processes. Some have been designed as structural materials and others have been designed to perform various functions such as healing the sick or killing pests and weeds. Obviously some chemicals are useful but many are toxic and their harm to the environment and our health far outweighs their benefit to society. We need to manage the risks better by only using chemicals, which are safe.
Chemicals enter air as emissions and water as effluent. Industrial and motor vehicle emissions of nitrogen and sulphur oxides cause acid rain, which poisons fish and other aquatic organisms in rivers and lakes and affects the ability of soil to support plants. Carbon dioxide causes the greenhouse effect and climate change. Chlorofluorocarbons (CFCs) cause the destruction of ozone in the stratosphere and create the possibility of serious environmental damage from ultraviolet radiation. Chemical fertilisers and nutrients run-off from farms and gardens cause the build up of toxic algae in rivers, making them uninhabitable to aquatic organisms and unpleasant for humans. Some toxic chemicals find their way from landfill waste sites into our groundwater, rivers and oceans and induce genetic changes that compromise the ability of life to reproduce and survive.
The impact of human activities on the environment is complex and affects a chain of interconnecting ecosystems. The extinction of species all along the chain may mean the loss of useful genetic material or life saving cancer drugs or safer alternatives to the dangerous chemicals in use at the moment.
Organochlorines
Organochlorine compounds such as polychlorinated biphenyls or PCBs were developed originally for use in electric equipment as cooling agents and are very dangerous chemicals. During the manufacture and disposal of products containing PCBs, and as a result of accidents, millions of gallons of PCB oil have leaked out. Although their manufacture in the United States was halted in the 1970s and they are being phased out, they are difficult to detect, are nearly indestructible and large quantities remain in existence and they will remain in the environment for a long time. They accumulate in the food chain and significant levels of them have been found in marine species, particularly mammals and sea birds, decades after their production was discontinued. They are carcinogenic and capable of damaging the liver, nervous system and the reproductive system in adults. When PCBs are burned, even more toxic dioxins are formed.
Dioxins
Dioxins, are a class of super-toxic chemicals formed as a by-product of the manufacture, moulding, or burning of organic chemicals and plastics that contain chlorine. They are the most toxic man-made organic chemicals known. They cause serious health effects even at levels as low as a few parts per trillion. Only radioactive waste is more toxic. They are virtually indestructible and are excreted by the body extremely slowly. Dioxins became known when Vietnam War veterans and Vietnamese civilians, exposed to dioxin-contaminated Agent Orange, became ill.
Dioxins enter the body in food and accumulate in body fat. They bind to cell receptors and disrupt hormone functions in the body and they also affect gene functions. Our bodies have no defence against dioxins which may cause a wide range of problems, from cancer to reduced immunity to nervous system disorders to miscarriages and birth deformity. The effects can be very obvious or subtle. Because they change gene functions, they can cause genetic diseases to appear and they can interfere with child development. Attention Deficit Disorder, diabetes, endometriosis, chronic fatigue syndrome, rare nervous and blood disorders have been linked to exposure to dioxins and PCBs.
Over the past 40 years there has been a dramatic increase in the manufacture and use of chlorinated organic chemicals in plastics, insecticides and herbicides. Dioxins have been found in high concentrations near to the sites where these chemicals have been produced and where insecticides and herbicides have been heavily used, such as on farms, orchards, or along electric and railway lines. They have also been a found downstream from paper mills where chlorine chemicals have been used to bleach wood pulp.
In the last few years we have begun to discard our unfashionable household plastic products, together with industrial and medical waste by burning them in incinerators. Dioxins formed during the combustion process have been carried for hundreds of miles on tiny specks of ash and contaminated the countryside. They settle on pastures and crops and get eaten by cows, pigs and chickens. They get into lakes, streams, and ocean and are taken up by fish. They go through the food chain and appear in meat and milk and accumulate in the fat cells of our bodies.
Cadmium
Cadmium occurs naturally in the earth's crust combined with other elements. It is usually formed as a mineral such as cadmium oxide, cadmium chloride, or cadmium sulphate and although these compounds are highly toxic they are less harmful when bound to rocks. They are present in coal and in the soil.
Cadmium is useful because it doesn't corrode easily. It is used in batteries, plastics, pigments and metal coatings. Cadmium gets into the environment through landfills, poor waste disposal methods and leaks at hazardous waste sites. It is produced by mining and other industrial activities. Cadmium particles enter our air when we burn coal for energy and incinerate household waste. The particles can travel far before falling to the ground or water. Each year many tonnes of cadmium are discharged into our seas and oceans. Animals and plants take up cadmium when it is in the environment. If we consume food contaminated with cadmium it can irritate our digestive system and cause vomiting and diarrhoea. If inhaled it can damage our lungs. Even when levels of exposure are low, over time, cadmium accumulates in the body and it can be difficult to get rid of. Accumulated cadmium can cause kidneys and bone disease.
We take cadmium into our body by: * Inhaling it when working in factories that make batteries or do welding, brazing or soldering * Inhaling it when near power stations or factories burning of fossil fuels * Eating foods in which it accumulates such as shellfish, liver and kidney * Drinking water that is contaminated * Smoking cigarettes
Conclusion
Potentially dangerous chemicals such as these are being introduced into the environment all the time. As in the case of PCBs their effect on living things may not be known until many years after their release. Hundreds of thousands of different chemicals are marketed worldwide. Of these 5000 are produced in quantities over 10 tonnes a year and 1500 are produced in quantities over 1000 tonnes year.
We do not have enough information about the environmental effects of these industrial chemicals and their effects on humans. The balance between human activity and ecological sustainability is wrong.
What you can do
Use biodegradable products. Make your own cleaning agent using safe materials. Dispose of chemical waste carefully. Do not put them down the sink. Be wise with home maintenance and in the garden. Do not burn plastics.
Avoid all organic chemicals that have "chloro" as part of their names including wood preservatives, herbicides and insecticides. Avoid chlorine bleach (sodium hypochlorite) and products containing it. Use oxygen bleach instead. Use unbleached paper products.Avoid "Permethrin" flea sprays for pets. Avoid products made of or packaged in polyvinyl chloride (PVC). Avoid cling flim plastic wraps unless they are clearly identified as non-chlorinated plastic.
To minimise your risk of dioxins accumulating in your body avoid all full-fat dairy products and fatty meats such as beef or pork. Wash all fruits and vegetables to remove chlorophenol pesticide residue. Avoid grapes and raisins unless they are clearly labelled as organically grown. Avoid soaps, toothpaste and deodorants containing "triclosan," a chlorophenol.
We can reduce the dioxins if we stop producing PVCs and other chlorinated chemicals. If your local government sends its waste to an incinerator, request that they stop burning plastics and introduce a comprehensive recycling service. Write to companies and ask them to use safe substitutes to chlorinated plastics. Ask your supermarket to sell Totally Chlorine Free (TCF) products. Join or form a local environmental group campaigning against hazardous chemicals.
People who work with cadmium should take care not to inhale cadmium-containing dust and should avoid carrying it home from work on their clothes, skin or hair. Eat from a wide range of foods to prevent the risk of ingesting toxic levels of cadmium.