By Dr Sunil E Fernado :
Reduce, Reuse and Recycle are the three key requirements for minimizing pollution in order to make the environment greener and safer for the present and future generations to live in
Environmental Chemistry is the branch of chemical science that deals with production, transportation, reactions and fates of chemicals, in water, air, soil, and biological environments and the effects of human activities thereon. Pollution is an environmental contamination with man-made waste (pollutants).
Perhaps an appropriate definition for environmental pollution would be “the introduction of harmful pollutants into an environment that makes this environment uncomfortable, unhealthy and irritable to live in.” Environmental pollution takes place in water, air and the soil.
The attitude to the waste generated by the industry in the past is best illustrated by a quote: “By definition, any by-product of a chemical operation for which there is no profitable use is a waste.” The most convenient, least expensive way of disposing of waste is up the chimney or down the river. (American Chemical Industry — A History, W. Haynes, Van Nostrand Publishers, 1954)
Such attitudes have changed and now the goal is “to close the loop, recycle as much as possible, avoid discharge of pollutants or wastes, and apply principles of Industrial Ecology, Environmental Chemistry, and Green Engineering.”
In order to close the loop, it is necessary to clearly understand and deal with each area where pollution can take place. Reduce, Reuse and Recycle are the three key requirements to make the environment greener and safer for the present as well as the coming generations.
Industries generate atmospheric pollutants. The four main Green House gases generated by the industry are carbon dioxide, nitrous oxide, methane and water vapor. A Green House gas is capable of absorbing and emitting radiation in the form of heat and hence an increase in the generation of Green House gases results in global warming referred to as Green House effect.
The first two pollutants mentioned above not only irritate lungs but dissolve in water and contribute to the long-term destruction of the environment generating acid rain. In addition, Carbon Monoxide, generated together with Carbon Dioxide, especially during incomplete combustion of Hydrocarbons, Coal etc. displaces and prevents oxygen from binding to hemoglobin and causes asphyxiation.
It can also bind with metallic pollutants and make these more mobile in air and water. Though unsustainable farming practices also contribute to the release of Green House gases such as Methane, it is the industry which is the major culprit.
Some known facts about air pollution are:
• On average, it takes one to two years off the typical human life-span.
• Air pollution affects kids more than adults because kids breathe more air and spend more time playing outside.
• More pollutants are discharged into the air each year than are released to surface water, ground water, and land, combined.
• Industrial and domestic emissions contribute to atmospheric pollution of major cities like New Delhi and Beijing while generation of smoke from land clearings cause hazardous haze in Southeast Asia from time to time.
Fresh, clean drinking water is a necessity but is a limited resource on the planet. Though 70% of the earth is covered with water only 2.5 per cent of it is fresh water and around 1 per cent of it is available for direct human use. Industrial, agricultural and domestic wastes can contribute to the pollution of this valuable resource. The four main water pollutants are heavy metals, inorganic pollutants, organic pollutants and suspended particles.
Heavy metals include transition metals such as Cadmium, Mercury, and Lead, all of which can contribute to brain damage. Inorganic pollutants like Hydrochloric Acid, Sodium Chloride, and Sodium Carbonate change the acidity, salinity or alkalinity of water, making it undrinkable and unsuitable for animals and agriculture.
Organic pollutants not only emit odorous gases but also take up dissolved oxygen in water limiting its supply to other living organisms. This can result in green algae formation on the surface of water cutting off sunlight to submerged water plants and animals.
In addition, recent incidents of accidental oil-spills have created enormous damage not only to the environment but also to the livelihood of fishermen. This takes many years to rectify.
In addition to what the industry generates, the innocent farmer too contaminate the environment not only by irresponsible discharge of organic pollutants like animal and agricultural wastes but also by excessive use of pesticides and herbicides such as Chlorpyrifos (an organophosphate highly toxic to amphibians) and Paraquat, and its by-products, such as Dioxin. All these substances are highly lethal to the animals and many can readily absorb through the skin.
Fine particles (solids) can stay suspended in water creating cloudy or turbid water. Large amounts of such particles not only can degrade aquatic habitat, but have been known to impair navigation and increase flooding.
These forms of pollutants affect the health of living forms in different ways.
•Heavy metals can accumulate in nearby lakes and rivers. These are toxic to marine life such as fish and shellfish, and subsequently to the humans. Heavy metals can slow development and result in birth defects while some are carcinogenic.
•Industrial wastes often contain many toxic compounds that damage the health of aquatic animals and those who eat them. They can cause immune suppression, reproductive failure or acute poisoning.
•Organic matter and nutrients cause an increase in aerobic algae and depletes oxygen from the water column. This causes suffocation of fish and other aquatic organisms.
•Inorganic pollutants such as Sulfate-based particles from acid rain can cause harm bringing about pH imbalance in the rivers and lakes.
•Suspended particles in freshwater reduce the quality of drinking water and the aquatic environment for marine life. Suspended particles can often reduce the amount of sunlight penetrating into the water, disrupting the growth of water plants and micro-organisms.
Soil pollution is defined as the build-up in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease-causing agents, which have adverse effects on plant growth and animal health. The ways in which soil pollution can occur are:
• Seepage from land fill
• Discharge of industrial wastes into the soil
• Percolation of contaminated water into the soil
• Rupture of underground storage tanks
• Excess application of pesticides, herbicides or fertilizers
• Solid waste seepage
The most common chemicals involved in causing soil pollution are: Petroleum products, Heavy metals, Pesticides and Solvents
The effects of pollution on soil are quite alarming and can cause huge disturbances in the ecological balance and health of living creatures on earth. Soil pollution affects soil fertility, loss of its nutrients, the balance of plants and animals residing in the soil, increase salinity making it unfit for vegetation, creation of toxic dusts, emanate noxious smells, and alter soil structure and hence the death of many organisms in it.
Generally, crops cannot grow in such polluted soils but those that manage to establish themselves would be toxic to animals.
Harmful effects of Industrial pollution was brought home to public attention in the 1970’s, and the history of an incident near Niagara Falls in the US is described at a University of Buffalo website. From 1942 to 1953, several chemical companies dumped 20,000 metric tonnes of chemical waste at this site.
In 1953, the land was sold to the local Board of Education, and a school was constructed on the land together with housing facilities. Unfortunately, eighty different chemicals, including dioxins and polychlorinated biphenyls (PCBs), started to leach through the soil, and residents began complaining of odd smells in their houses and experiencing many unexplainable health problems. The school was closed in 1978, and the Federal Government funded the relocation of 200 families nearest the site.
One of the most unfortunate industrial accidents occurred in Bhopal in India in 1984 which is referred to as the Bhopal Gas Tragedy. A leak of Methyl Isocyanate gas and other chemicals from the Union Carbide plant resulted in the exposure and the death of around 3,800 people. The polluted soil and water in this area are reported to be adversely affecting the lives of the poor even after 32 years of this incident.
Even harmless-looking small ventures such as Metal finishing (plating) deal with deadly chemicals which can be a threat to animals and plants alike. For example, Cyanide compounds are used in plating baths, to remove tarnish or other undesirable films from surface, and to deposit an even metal deposit. Metal coatings of Cadmium, Iron, Gold, and Zinc often use cyanide compounds. These can become a threat if not handled carefully and disposed of appropriately.
Chromium coatings provide excellent wear resistance and corrosion protection, as well as a bright, highly reflective surface. Acidified Dichromate is another form of Chromium used in the industry for cleaning purposes since it oxidizes any organic residue almost instantaneously.
The form of Chromium that is of major health concern in metals plating and also in cleaning is Hexavalent Chromium, which is highly toxic due to its strong oxidation characteristics and high membrane permeability.
Long-term exposure to Hexavalent Chromium can result in irritation of the nasal mucous membrane, including formation of ulcers, and has been associated with an increase in lung cancer. The safest way to dispose of hexavalent Chromium is to convert it to the trivalent form which is sparingly soluble in water.
The after-effects of Hexavalent Chromium came to light following an incident in California when a case was settled with the largest settlement ever paid till 1996. The case alleged Pacific Gas and Electric Company discharged Hexavalent Chromium, used to minimize corrosion to an unlined pond thereby contaminating the area in the vicinity.
The case was settled for US$ 333 million when an American legal clerk Erin Brockovich-Ellis filed a case against the company. This whole episode became famous when a film titled Erin Brockovichwas released in 2000 where M/s Julia Roberts played the part of Erin.
Industrial pollution is one of the leading causes of pollution worldwide. In the United States, the Environmental Protective Agency estimates that up to 50% of the nation’s pollution is caused by the industry.
Because of its size and scope, industrial pollution is a serious problem for the entire planet, especially in nations which are rapidly industrializing. Unfortunately, semi-industrialized countries are not immune to the after-effects as pollutants do not respect borders or boundaries.
Industrial pollution dates back to antiquity, but accelerated rapidly in the 1800’s, with the start of the Industrial Revolution. Following mechanization and increased production, the problem was compounded by the use of fuels like coal which is highly unclean, and poor understanding of the causes and consequences of pollution.
Role of the industry
The study of Environmental Chemistry in the Industry should start at the beginning. If it is not understood clearly, it can lead to pollution of the workplace and then the rest of the environment causing havoc in the end. Understanding Environmental Chemistry of unit processes practised is the first and the fundamental step that is needed to contribute to a “greener environment” for the present and also for the next generation.
Having considered the ill-effects of the pollutants generated, the question that needs to be addressed by the industry is: Are we doing the needful to minimize pollution by generating less pollutants? In any type of industry, large or small, to find answers to this question is to look at the operation from the beginning.
This applies to the Rubber and Plastics Products Manufacturing Industry as well despite the fact that it is not a primary industry producing raw chemicals but involved in manufactured products sold direct to the consumer.
Even in simple operations like drying of natural rubber, smelly substances are released that can contaminate the neighborhood. Such odorous components, when analyzed using gas chromatography/mass spectrometry (GC/MS), were found to contain low molecular weight volatile fatty acids (C2-C5) and other volatile organic contents including carbonyl compounds, low molecular weight compounds with nitrogen or sulfur and aromatic compounds.
It is interesting to note that the total content and composition of volatile organic compounds can be directly correlated to the rubber quality and the drying process. Low-grade natural rubber samples, for example TSR 20 from cup lumps with intense smell, have high quantity of volatile organic contents, especially low molecular weight volatile fatty acids.
On the other hand, high-quality rubber such as de-proteinized natural rubber, TSR L, and Latex Crepe grades from which no smell was detected, contained only minute quantities of volatile organic contents. Aromatic components are regarded as other major odorous contents found in Ribbed Smoked Sheet (RSS) samples.
The results suggest that the odorous components were the by-products of non-rubber components which had undergone microbial breakdown during storage or thermal degradation during processing. Thus, when processing low grade raw rubber, appropriate measures are needed to remove such substances when such processing is done in appreciably large quantities.
In the products manufacturing industry as well, this rule applies. The importance of the use of right clean raw material and the appropriate process is a good environmental practice. This will not only give a better quality product but also assist in reducing contamination of the environment.
In dry rubber and plastic compounding chemical dust contamination of the environment is a major source of air pollution. Though dust seemingly disappears when the process is over, the after-effects remain for a longer period of time despite it being nearly invisible. Dust not only gets carried by the wind but also by those who operate machines and equipment. The long-term effects of inhalation of such dust are well-documented.
Though the rubber products manufacturing industry has the potential to pollute, the natural rubber industry by itself indirectly contributes to the cleaning up of the environment on a massive scale. This has gone largely unnoticed by the modern-day environmentalists as well.
Millions of hectares under natural rubber plantations help fix massive amounts of Carbon Dioxide emitted by burning of fossil fuel etc into a more useful solid rubber carbon sink by a natural process. Thus extraction and use of more natural rubber is a positive greener way of contributing to the environmental cleanup and saving of the planet.
Plastic products industry
Those managing the Plastic Processing industry should be aware of the following in order to understand Environmental Chemistry relating to the industry.
1. Impact of plastic materials
Natural and synthetic polymers and their compatibility with surroundings, life expectancy of different plastics, thermal degradation, biodegradation and photo degradation of plastics, chemistry and the nature and impact of additives used for increasing the durability of polymers.
2. Pollution and hazards related to plastics
Pollution caused by plastics, transfer of chemicals from plastics to the soil and water (including additives, flame retardants, chlorinated additives etc.), standards regarding limits of these chemicals in effluents.
3. Re-usability and reprocessing of plastics
Need and importance of reprocessing, stages in recycling (primary, secondary and tertiary), advantages and disadvantages of recycling.
4. Plastic waste management
Public awareness of the hazards caused by indiscriminate use of plastics, proper disposal of plastics, collection of recyclable plastics, landfill and incineration processes.
There are about 50 different groups of plastics, with hundreds of different varieties available to us. All types of plastics are recyclable. To make sorting and thus recycling easier, SPI resin Identification code with a symbol for use internationally has been developed by the Society of Plastics Industry (SPI) so that before recycling, plastics can be sorted accordingly.
Recycling symbol for Polyethylene Terephthalate
In addition to the contamination of air and soil, manufacturing of plastic articles and rubber products consume considerable amount of energy. Whether it is coming from electrical or heat energy, manufacturers should be aware that excessive use not only add to cost of production but also results in unnecessary contamination of the environment.
Rubber products industry
The Environmental Chemistry involved in rubber products manufacture differs in the type of main raw material used. In the case of solid rubber processing it is basically similar to the plastic industry. In the latex industry, in addition to the possibility of air pollution, water pollution could become a hazard if not dealt with appropriately.
In the latex industry, considerable amount of water is used for product manufacture at various stages
of production. Therefore, control in the use of water and its contamination should be monitored for each unit process.
It is necessary to isolate effluent from these unit processes for better control in the treatment process at a later stage. This is an industry where reduce, reuse and recycle can be effectively demonstrated.
The effluent in the latex products manufacturing industry contains not only residual chemicals but also proteins, carbohydrates from natural latex and also emulsifiers used in the production of synthetic latex.
However, efficient methods have been developed and successfully applied to treat such effluent not only to minimize further contamination but also to reuse treated water in substantial quantities. An understanding of sedimentation processes, anaerobic and aerobic processes and membrane technology in removing contaminants is an essential part of this cleaning-up process.
Towards cleaner environment
In order to achieve the objective of a cleaner and greener environment, it is necessary to:
• Understand Environmental Chemistry of each unit processes in a production process.
• Continuously improve the environmental, health, safety, knowledge and process technology.
• Use resources efficiently and minimize waste.
• Report on performance, achievements and shortcomings.
• Engage, educate and work with people to understand and address their concerns and expectations.
• Cooperate with governments and organizations in the development and implementation of effective, meaningful regulatory standards.
• Provide help and advice to effectively manage all aspects of the process, from raw materials to finished goods and final disposal of the product
• Inform and educate the customers and consumers alike regarding benefits of safe handling and safe and appropriate disposal of products.