CHEMICAL POLLUTION: CAUSES, CONSEQUENCES, EXAMPLES - ENVIRONMENT - 2024

The chemical pollution is the introduction into the environment of chemicals that alter its quality causing a negative effect. The pollutant can be toxic by itself or react with other substances in the environment and alter its properties.

Chemical contaminants can be solid, liquid and gaseous of both organic and inorganic origin. Its field and level of action depend on many factors, among which are its solubility and reactive capacity.

Chemical contamination of water. Source:

This type of contamination can occur by chemicals of natural or artificial origin. The main interest in dealing with chemical pollution of the environment is related to the anthropogenic contribution of chemical substances to the environment.

Sources of chemical contamination are diverse, including domestic, commercial, transportation, industrial, mining and agricultural activities.

Chemical pollution is considered one of the most serious threats to life on the planet. Many of the chemical pollutants are toxic to wildlife and humans, and others alter the properties of water, air, and soils.

Some processes triggered by chemical pollution are quite serious like global warming. Another serious problem is the release of heavy metals into the environment.

There are many examples of chemical contamination worldwide, such as the stretches of the Bogotá River (Colombia) without aquatic life or the Dead Zone of the Gulf of Mexico.

As for effects on particular groups of organisms, there is the case of the decline of amphibian populations. Another example is the effect of chemical contamination on food quality and public health.

A well-known example is the contamination of fish and shellfish in Japan's Minamata Bay by mercury spills. This caused an epidemic manifestation of a childhood neurological syndrome (Minamata disease) and serious conditions in adults.

Solutions to chemical contamination are diverse, encompassing prevention and restoration or remediation. Prevention requires implementing a new ecologically friendly economic and social development model.

For this, it is necessary to control chemical waste in all its forms, solid waste, gas emissions and urban and industrial effluents.

Various technological alternatives are used to remedy chemical contamination, depending on the nature of the contaminant and the environment. Physical remediation is applied by removing or blocking contaminants, or chemistry to neutralize or degrade them.

characteristics

Oil pollution in Louisiana (United States). Source: US Coast Guard

- Chemical pollutant

It is any substance that causes a deviation or alteration in the average chemical composition of a certain environmental system. This alteration affects quantitatively or qualitatively the benefits that the environment provides to human beings.

- Solubility

Each chemical contaminant has a preponderant affinity for a particular medium based on its solubility. For example, CO2 mainly affects the atmosphere, while an organochlorine (DDT) soluble in fats and organic solvents accumulates in living beings.

- Nature of pollutants

There are organic chemical pollutants such as most pesticides, dioxins, and hydrocarbons. Other chemical contaminants are inorganic, as is the case with heavy metals. Likewise, some contaminants have a mixed nature like many detergents.

Chemical properties

The mode of action and the effect of each chemical pollutant vary with its chemical properties. They are given by their molecular structure which determines their affinities and reaction capacities.

- Effect of chemical pollutants

Toxic and bioaccumulative

Chemical contaminants can be directly toxic, causing injury or death by effect on cells, tissues or organs. This effect can be cumulative and occurs in the individual and along the trophic chain (bioaccumulation).

They alter ecological processes

Some pollutants exert their effect by altering ecological processes, such as organic nutrients that generate eutrophication. It is the increase in nutrients in a body of water that causes a population explosion of algae and bacteria, affecting the oxygen content in the water.

Mixed effect

Some chemicals, such as phosphate detergents, have a double effect by being toxic and triggering ecological processes such as eutrophication.

Causes

- Urban

Effluents

Modern cities use myriad chemicals in both homes and workplaces. Most of these end up as waste in sewage systems or being diverted to the atmosphere.

Every household in the city incorporates detergents, oils, fats, disinfectants and organic residues (including food waste and human excreta) into its sewage. Disposable cartridges for printers, stationery and other elements that contribute chemical substances to the environment are also generated in the work areas.

Plastic pollution off the coast of Ghana. Source: Muntaka Chasant

Solid waste

Huge amounts of garbage are generated in urban centers, especially in large overcrowded cities. If these wastes are not properly managed, they can incorporate polluting chemicals into the environment.

- Transportation

Urban and interurban traffic

Motor vehicles expel gases, fuel residues, oils and fats into the environment. These generate enormous amounts of carbon dioxide (CO2) and monoxide (CO), nitrogen oxides, sulfur dioxide, lead and other elements.

Carbon monoxide is a highly toxic gas even in small amounts and in low proportions it is oxidized in the environment to form CO2.

Aquatic transport

Freight transport and fishing fleets pollute the waters with traces of fuel, oil and organic waste. A relevant case is the transport of oil, since accidents occur periodically with spills into the sea from tankers.

- Industrial

Metallurgical industry

This industry uses large amounts of energy in its smelting furnaces, releasing greenhouse gases. Additionally, production wastes contribute heavy metals in their effluents.

Textile industry

It is one of the most polluting industries because it uses various chemicals in its processes and generates a large amount of waste. Products such as chlorinated anilines, perfluorooctanoic acid and chloronitrobenzene, have been detected in discharges from the Chinese textile industry.

These substances have a negative impact on aquatic life and some are carcinogenic.

Paper industry

Paper bleaching processes use chlorine and produce dioxins, mercury, and other contaminants.

Thermoelectric Industry

Most CO2 air pollution comes from burning coal in the thermoelectric industry. This process is one of the major sources of environmental mercury and of heavy metals in general.

Pharmaceutical industry

In recent times, new polluting substances have been detected in the environment, being called emerging pollutants. Among these are drugs, both for human use and those used in animal health.

These products enter the environment as waste from the pharmaceutical industry, medical waste or products whose useful life has expired.

- Oil and byproducts

Oil production

Conventional oil production generates so-called drilling or extraction muds laden with chemical pollutants. The main chemical pollutants are hydrocarbons and heavy metals.

Modern techniques used for the extraction of gas and residual oil, such as fracking or hydraulic fracturing, are especially polluting. The 600 different chemicals used to dissolve the rock and facilitate extraction pollute soils and waters.

Refining and derivatives

Oil refining produces chemical pollution in the form of residues throughout the process, especially by hydrocarbons and heavy metals. Later, the products generated also end up contaminating the environment.

- Mining

Mining is one of the activities that causes the most negative impact on the environment by using chemical pollutants such as mercury and arsenic.

Gold mining

In open pit gold mines, arsenic is used accompanied by hydraulic fracturing processes to separate the gold from the rock. This incorporates both arsenic and other heavy metals that are released from the fragmented rock into the soil and water.

- Agriculture and breeding

intensive agriculture

Modern agriculture uses large amounts of chemicals, such as fertilizers and pesticides. More than 40% of the applied fertilizer is not used by the plants and is leached to the water sources.

Fertilizers provide nitrites, nitrates and heavy metals, for example cadmium in the case of organic phosphate fertilizers. Regarding pesticides, agriculture uses a variety of polluting chemicals such as herbicides, insecticides, acaricides and fungicides.

Breeding

Intensive animal production systems mainly contribute organic waste, including excreta and animal remains. One of the most polluting systems in this regard is pig production.

Main chemical pollutants

- Industrial and combustion gases

Carbon dioxide (CO2)

It is generated as a by-product of the combustion of organic matter or fossil fuels, as well as in the process of aerobic respiration. In both respiration and combustion, carbon reacts with oxygen and is released as a gas.

Although it is not a toxic gas, in large quantities it has negative effects on the atmosphere. Upon reaching the stratosphere, it destroys the ozone layer (O3) responsible for filtering ultraviolet radiation, contributing to global warming.

It is also subjected to photochemical reactions generating carbonic acid (H2CO3) that precipitates with water in the form of acid rain.

Nitrogen dioxide (NO2) and Nitrous oxide (NO)

Nitrogen oxides (NOx) are produced from both natural (volcanic eruptions) and man-made sources. Among the latter are the burning of fossil fuels and the burning of solid waste.

Once in the troposphere, nitrogen oxides react with water vapor, OH radicals and tropospheric ozone (O3) to produce nitric acid (HNO3). This acid later precipitates with rainwater, forming what is called acid rain.

Sulfur dioxide (SO2)

The main anthropic source of sulfur dioxide is the burning of coal, especially in thermoelectric plants. SO2 is also part of photochemical reactions in the troposphere.

This substance can react with OH, HO2, CH3O2 radicals, water, ozone, hydrogen peroxide (H2O2) and metal oxides. The result is the formation of sulfuric acid (H2SO4) that is part of acid rain by precipitating together with rainwater.

As for its impact on public health, SO2 fundamentally affects the respiratory system.

- Heavy metals

Although there are various heavy metals that act as chemical pollutants and multiple human activities that generate them, the most relevant are:

Lead

It is used in the manufacture of pipes, batteries, glass, as an anti-radiation barrier and many other uses. Until 1985 it was an antiknock component of gasoline in order to increase its octane number (tetraethyl lead).

It was also an ingredient in paints, so old buildings and their debris are a source of lead contamination. In addition, lead as a soil pollutant is absorbed by crops and from there is ingested to humans.

Pollutant particles in the air that can be inhaled and cause lead poisoning in humans. It causes developmental delays in children and neurological problems in adults.

Mercury

It is an element present in many compounds frequently used such as fungicides and paints. However, the largest source of environmental mercury production is burning coal for fuel.

It is also used in mining in the extraction of some metals such as gold. It is a highly toxic bioaccumulative compound and can affect the nervous and endocrine systems.

Cadmium

This compound is not found in free form in nature, but it is released by humans in the smelting of metals (copper, zinc). It is also emitted into the environment from fossil fuels (coal, petroleum derivatives).

It is also used in the manufacture of batteries and PV plastics and in phosphate fertilizers. Cadmium pollutes soil and water, and is absorbed and accumulated by cultivated plants.

For example, cadmium-contaminated soils contaminate cocoa, which then passes into chocolate.

Arsenic

Soil and water pollution by arsenic can originate from natural or artificial sources. Among the latter are mining, drugs, lacquers and varnishes, ceramics, and other products.

Arsenic is a highly toxic bioaccumulative compound that causes nerve problems, kidney disease, and even death.

- Pesticides

They are chemical compounds expressly formulated to combat weeds or pests. This encompasses a large number of chemical compounds of different nature, both organic and inorganic.

It includes insecticides (to combat insects), acaricides (for mites), fungicides (pathogenic fungi) and herbicides (against weeds). In bacterial infections antibiotics are applied.

Herbicides

For example, on cotton (Gossypium barbadense) numerous airplane flights are applied spraying different products, both herbicides and insecticides. 10% of the pesticides produced worldwide are used in this crop.

Insecticides

Insecticides are not very selective regarding the type of insect they affect, so they end up causing serious damage to the biodiversity of the areas near the crops. In fact, one of the serious contemporary problems is the reduction of the populations of bees (pollinators) and other hymenopterans due to the action of agrochemicals.

- Detergents and surfactants

These products are synthesized to eliminate fats and other compounds that dirty clothes, kitchen utensils, floors or any object that requires cleaning. They are used under different presentations and modalities both in homes and workplaces.

They are designed to break the surface tension and chemical bonds of different substances. Once they fulfill their purpose, they generally end up in the drain and if the effluents are not treated properly they go to water sources.

Impact

Once in the natural environment, they affect biological membranes, reducing the populations of beneficial aquatic microorganisms. This alters the trophic chains, since these microorganisms act as detritivores and decomposers.

They also affect fish and amphibians causing death or deformation in fingerlings and tadpoles and skin diseases in adults.

- Oils and fats

Animal and synthetic fats are produced as well as vegetable and synthesized oils. These products are used for various purposes such as cooking and medicinal use to the lubrication of machinery.

Therefore, they form a continuous surface layer that hinders gas exchange and affects the oxygenation of the water. In addition, by impregnating the feathers of birds, it cancels its thermal insulating effect and causes death.

- Dioxins

They are produced in various processes especially where combustion is involved with the intervention of chlorine. The combustion of petroleum products is another important source of dioxins, especially the burning of plastic waste in landfills.

Consequences

- Atmospheric disturbances

Global warming

Gases such as CO2, Nox, SO2, methane and others generated by anthropic activities produce the so-called greenhouse effect. In some cases they destroy the ozone layer responsible for reducing the penetration of ultraviolet radiation.

Additionally, they prevent the exit of long-wave heat radiation into space. The result is that the average temperature of the planet has increased progressively since the industrial revolution.

Acid rain

Acid precipitation is caused by the incorporation into rainwater of acids generated in the troposphere. It is a precipitation with a pH lower than 5.6 that acidifies the soil affecting agriculture and also water bodies.

In some cases, acidification of the soil releases aluminum that becomes available to plants and is toxic. This compound is also carried into bodies of water and affects aquatic fauna.

- Degradation of ecosystems and loss of biodiversity

Aquatic ecosystems

Rivers, lakes, seas and oceans are increasingly affected by chemical pollution. Heavy metals, oil, plastics releasing dioxins, untreated effluents that carry organic and inorganic substances pollute the waters.

Fertilizers and pesticides generate eutrophication processes and produce dead zones.

Terrestrial ecosystems

Chemical contamination of soils and water affects plants and through the trophic chain it spreads to the entire ecosystem. Insecticides decrease natural insect populations and acid rain affects sensitive groups such as amphibians.

Bioaccumulation

Bioaccumulation refers to chemicals soluble in organic compounds that accumulate in tissues when consumed by animals. In a food chain this implies an exponential increase in the concentration of the toxin.

For example, insects consume herbicide-treated leaves and accumulate the molecule in their bodies. Then the frogs consume many insects, accumulating a greater amount of the poison.

Eventually, a raptor consumes several frogs, reaching an even higher concentration of the toxic molecule.

Some chemicals susceptible to bioaccumulation are some herbicides (DDT, Endrin, Parathion and others), flame retardants (PBB, PBDE), mercury and other heavy metals.

- Reduction of food production and quality

Food production

When soils are contaminated, the yield or production of poor quality crops is reduced. Watering with contaminated water is a serious health risk when consuming these vegetables.

The fishing industry and other marine and river products are seriously affected by chemical contamination of the water. Fish populations are declining, as are crustaceans, bivalves and mollusks.

Food contamination

Chemical contamination of food can originate in the field, due to poor handling of agrochemicals or during food preparation and handling.

Plant products can become contaminated with heavy metals by absorbing them in contaminated soils. Farmed animals may contain bioaccumulative chemical contaminants in their tissues.

Marine foods such as fish and crustaceans can be contaminated with mercury.

During food preparation, chemical contamination with cleaning products or excessive use of preservatives can occur. It has been pointed out that some plastic containers can incorporate dioxins into the liquids they contain.

- Decrease in drinking water

Drinking water is an increasingly scarce resource, so its quality must be guaranteed. Chemical contamination seriously affects the quality of water that can become toxic to humans.

Contamination of water with heavy metals, detergents, hydrocarbons or other toxic substances makes it unusable for consumption. On the other hand, water purification to remove toxic pollutants is costly.

- Public health problems

Most chemical pollutants cause health problems for humans or pets. In some cases, such as ingestion of arsenic or mercury, the consequences can be fatal.

Examples

- Dead zones of rivers and seas

Chemical contamination of water generates various processes that end up killing life in large areas.

One element is the direct toxicity of some inorganic chemicals such as heavy metals, flame retardants or detergents. Another factor is eutrophication caused by the incorporation of organic compounds.

For example, rivers like the Bogotá (Colombia) have extensive stretches where no life is detected. This is due to chemical contamination from untreated urban and industrial effluents.

The same occurs in a large area of ​​the Gulf of Mexico at the mouth of the Mississippi River. In this case as a consequence of the contribution of tons of fertilizer and pesticide residues.

- Chemical pollution and amphibians

The problem

For several decades now, there has been a warning of the decline in amphibian populations, especially toads and frogs. This phenomenon is accompanied by the appearance of congenital malformations in animals.

Among the possible causes of the affectation of amphibians is the chemical contamination of their habitats. It is estimated that around 17% of amphibian species are threatened by chemical contamination.

Physiological bases

Amphibians are highly susceptible to the presence of pollutants in the air and water, mainly due to their skin respiration. That is, these animals carry out oxygen exchange through their skin, which is highly sensitive to the irritating effect of chemicals.

- Minamata disease (Japan)

Between 1932 and 1968, the Chisso company was producing acetaldehyde and vinyl chloride using mercury chloride as a catalyst. This company dumped wastewater into the sea without proper treatment.

Minamata disease (Japan). Source:

The inhabitants of Minamata Bay consumed the contaminated fish from the area and accumulated mercury in their bodies. In the 50s of the 20th century, a childhood neurological syndrome was detected in the coastal community of Minamata.

Investigations showed that the cause of the condition was the ingestion of fish and shellfish contaminated with mercury.

Mercury affected pregnant mothers, producing irreversible neurological disorders in children. By 2009, more than 10,000 cases and 2,271 victims had been identified.

From this case arose the Minamata Agreement, an international agreement to prevent environmental pollution by mercury.

- Other cases of mercury contamination

Other epidemic cases of mercury contamination have occurred. In Japan (1965), due to the dumping of waste from another acetaldehyde-producing company into the Agano River (690 victims).

In Canada (1862-1970) a pulp mill generated mercury discharges and caused poisoning in an aboriginal town (Grassy Narrows). In Iraq (1970) about 10,000 people died and others suffered brain damage from consuming wheat treated with methylmercury.

Solutions

- Prevention

Preventing the emission of chemical pollutants into the environment is the first measure to solve chemical pollution. This involves a complex program of measures that include educational, legal and technical aspects.

Conscience and laws

It is necessary to raise awareness regarding chemical contamination, its causes, consequences and solutions. On the other hand, an adequate legal order is required to restrict and sanction the emission of pollutants.

Technical elements

It is necessary to generate a waste management plan that starts from the principle of reducing, reusing and recycling. This implies increasing the efficiency of industrial processes and a sustainable approach to development.

There are several technological alternatives to filter the gases that are emitted, properly process effluents and solid waste.

- Restoration

Once the chemical contamination has occurred, it is necessary to resort to restoration or remediation measures. The technologies to be used will depend on the nature of the chemical contamination and the contaminated environment.

Air pollution

There are no effective remediation measures for polluted air except in confined areas. In this case, it is only possible to eliminate the polluting sources and thus allow the ecosystem itself to regulate itself.

Water contamination

Contaminated water can be purified through treatment plants and nanotechnologies (nanobubbles) are currently being applied to decontaminate water.

Soil contamination

Soils can also be subjected to both physical and chemical restoration processes. These can be applied on site or by moving the soil mass to a place conditioned for it.

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