Everything in the world around us is made up of chemicals. Living organisms such as plants, animals and humans are all made up of chemicals. Chemicals are integral part of daily life of people around the world. Use of chemicals around the world is increasing with the growing production in countries. Chemicals have played a major role in the development of human societies – in agriculture and food; in industry and transport; in housing and in health. The entire World has poisoning itself with the “miracle of modern chemistry” as found in all the pesticides, plasticizers, additives, preservatives, detergents and other chemicals. Chemical impacts are complex, unknown. Chemicals can enter the air, water and soil, when they are produced, used or disposed. These chemicals are known to exhibit various harmful effects on human biology, covering everything from neurological and infertility problems to cancer and hormonal disorders.
Over 11 million chemical substances are known and some 60,000 to 70,000 are in regular use. Between 200 and 1000 chemicals are produced in excess of one tonne annually. Currently new chemicals are entering the market at the rate of about 600 each month (or over 7000 per year) (Lillibridge 1997). Of the 80,000 chemicals in general use, only about 3,000 have been stringently tested for health impacts on humans. A new study from the University of California, San Francisco reveals that 100 percent of expectant mothers are contaminated with highly toxic synthetic chemicals. The study, published in Environmental Health Perspectives, concluded, “certain PCBs, organochlorine pesticides, PFCs, phenols, PBDEs, phthalates, polycyclic aromatic hydrocarbons (PAHS) and perchlorate were detected in 99 to 100% of pregnant women.”
Chemical contamination may originate from manufacturing, processing, transportation, storage, distribution, use and waste disposal. Chemical incidents can happen anywhere and at anytime. Lorries can spill their contents, rail tankers can overturn and clouds of chemical vapour can drift anywhere in the wind. More than 4 billion tonnes of hazardous chemicals are moved each year around the world by motorway, rail, and pipeline systems.
Persistent, bioaccumulative and toxic (PBTs) substances are a class of compounds that have high resistance to degradation by abiotic and biotic factors, high mobility in the environment and high toxicity to cause birth defects, cancers and other health effects. PBTs transfer easily among air, water and land and cross human boundaries. The U.S EPA has identified 31 as PBTs (28 organic chemicals plus 3 metals and their compounds) e.g., Polychlorinated chemicals (e.g., DDT, PCBs), Poly brominated chemicals (e.g., organo-bromines), Poly fluorinated chemicals (e.g., organoflurorines), benzopyrene, alkyl-lead and mercury compounds.
Polycyclic aromatic hydrocarbons are a family of long lived chemicals that cling to sediments, bioaccumulate in fats and difficult to degrade. PAHs are similar to PCBs and other polychlorinated chemicals but PAHs do not contain chlorine. They are produced by incomplete combustion of fossil fuels and wood burning. Natural PAH sources include forest, grass fires and volcanic eruptions. Air borne PAH particulates settle on the water, food, crops and other vegetation. The route of 90% of human exposure to PAHs is from food consumption, especially leafy vegetables and unrefined grains. Breathing air borne PAH particulates cause respiratory distress. Benzopyrene is a best known human carcinogen.
Volatile organic chemicals (VOCs) are chemicals that transform quickly from liquid to vapour. VOCs are found in paints, paint thinners, lacquers, hair sprays, perfumes, oven cleaners and dry cleaning liquids. VOCs also emanate from wood finishes, plywood, panelling, fibreboards, particleboards, carpeting, furniture, permanent- press fabrics, draperies and mattress ticking. Motor vehicle products such as gasoline and oils emit VOCs. VOCs contribute to the formation of ground level ozone. VOCs are soluble in water which can result in pollution. VOCs are flammable and can be toxic to humans and wildlife. One of the most widespread VOCs is formaldehyde, classified as a probable human carcinogen by the U.S EPA. It causes nasal cancer in laboratory animals and it irritates the eyes, nose, throat and lungs. Another common VOC, chloroform is a by-product of the process used to sanitise drinking water, in some water treatment plants. VOCs that accumulate in air tight buildings/cabins of jet planes contribute to ‘sick building syndrome.’
They form the basic raw materials in the manufacture of a large number of materials such as fertilizers (ammonia), plastics, fibres, rubbers (nylon, polyester, acetate etc.), and paints. They have also been used in the manufacture of pesticides, lubricants, adhesives and solvents. The production processes of ammonia, acetone, ethyl alcohol, acetic acid, acetic anhydride, glycerine significantly based on petrochemicals. Nearly more than 80% of the organic chemicals used in chemical industry are based on petrochemicals.
Some notable injurious chemicals
Phthalates are chemical plasticizers. Pharmaceutical pills are often coated with phthalates to give them a shiny finish. They’re also used in children’s toys, medical devices, personal care products, sunscreens and even sex toys. On the personal care side, phthalates are found in perfumes, eye shadow, liquid soap, nail polish and hair spray. Phthalates are known as “endocrine disruptors” because they interfere with normal endocrine system function — potentially leading to obesity and birth defects. Oxybenzone, the active ingredient in many sunscreens, is a hormone disruptor and could even damage the nervous system. Perchlorate, also known as the “rocket fuel chemical,” is used in the manufacture of automobile airbags and other vehicle parts. It’s also present in many fireworks, and is frequently found contaminating the water supply. Metal like mercury is highly toxic and its compound methyl mercury is a confirmed neurotoxicant. It builds up in the food chain, notably in certain food fishes and enters the human food chain. It damages the developing brain. It is also genotoxic: it is known to pass through the placental barrier and the blood-brain barrier putting the unborn at risk. It can cause permanent damage to the central nervous system, lungs and kidneys. Possible sources of metal contamination include residues migrating into foods from soldered cans, leaching from utensils, contaminated water, glazed pottery, painted glassware and paints.
General characteristics of hazardous chemicals
Toxicity is the inherent property of a chemical to produce adverse biological effect.
Mobility is the ability of a chemical to travel through the environment.
Persistence is the ability of the chemical to remain in the environment for a long time.
Synergistic action - the combined effect of two different chemicals is greater than the individual effect.
Bioaccumulation is the selective accumulation in the bodies of living organisms.Biomagnification – the concentration of bioaccumulated chemical in the bodies of living organisms increases as they travel up the food chain.
“Be aware of our potential exposure to hazardous chemicals in the home, workplace and environment.”
The Stockholm Convention and POPs
The Stockholm convention on persistent organic pollutants (POPs) 2001 is an international agreement by the nations of the world to address the global chemical pollution. It was signed by 128 country parties in 2001 and come into force from May 2004. POPs are chemical substances that persist in the environment, bioaccumulate through the food web and pose a risk of causing adverse effects to human health and environment. POPs include 12 chemicals (dirty dozen) such as the organochlorine pesticides: DDT, endrin, dieldrin, aldrin, chlordane, toxaphene, heptachlor, hexachlorobenzene, mirex; and the industrial chemicals and by-products: PCBs, dioxins, and furans. The Convention aims to eliminate the production, use and emissions of POPs.
Green chemistry is the science – based design of chemicals, chemical processes and products that minimize the use and generation of hazardous substances.
12- Guiding principles of green chemistry
1. Prevention –prevent waste generation.
2. Atom economy –design efficient design synthetic methods.
3. Less hazardous chemical syntheses- design production methods – less toxic by-products.
4. Design safer chemicals-minimum toxicity of products.
5. Use safer solvents and auxiliaries.
6. Design for energy efficiency.
7. Use renewable raw materials.
8. Reduce derivatives
9. Use catalytic reagents.
10. Develop in-process control of hazardous substances.
11. Prevent the potential for chemical accidents.
12. Design for chemical degradation.
Warnings for safe chemical use
Stay informed – be aware of the characteristics for e.g., toxicity of chemicals.
Choose non-toxic or less-toxic household products – follow instructions and warnings for safer use.
Make healthy diet and life style choices – avoid tobacco products. Choose fresh foods.
Reduce the potential for indoor and outdoor chemical exposures.
Get involved – participate in public policy development.