Environmental hazards are the natural or human induced accidents, risks or harms caused to the environment, which could subject living things to a material risk of death, injury or impairment of health. Environmental hazards management involves formulation of strategies for preventing, minimising or controlling these hazards.
Environmental hazards are created through the increasing use of resources and degradation of ecosystems by man. The ecosystem is a functional unit of the environment that includes all organisms (living things) and physical features (non-living things) within a given area. An ecosystem is degraded when its carrying capacity is exceeded, that is, when harmful impacts arising from human activities surpass what the ecosystem can restore naturally.
Environmental disruptions arising from these hazards can be classified into three main types:
(a) Resource Exploitation and Utilization. A resource is any source of raw materials. Resources include fuels, minerals, water, soil, timber, etc. Material resources can be depleted or degraded as follows:
(i) A resource is depleted as it becomes less available for its intended use. For examples, non-renewable resources like minerals, fuels, etc.
(ii) A resource can be degraded or rendered unfit for its intended use by pollution. If industrial or agricultural wastes are discharged into a stream, the stream becomes less fit for drinking purpose, for recreation, or for the support of aquatic life. In this way, pollution and resource degradation are interrelated.
(iii) A resource can be degraded by over-exploitation. An ecosystem is said to be degraded when it cannot support healthy organisms, or maintain its productivity, adaptability, and capability of renewal. Soil may be degraded in respect of agricultural productivity. In this regard, over-exploitation and resource degradation are very closely related to each other.
(b) Pollution. This is the reduction in the environmental quality by the introduction of impurities through human activities. Smoke and other air-borne pollutants pollute the air; Sewage, agricultural and industrial wastes pollute the water; and Solid and hazardous wastes pollute the land.
(c) Changes in the global climatic conditions due to human activities.
Environmental Hazards and Solutions
1) Indiscriminate disposal of solid and hazardous wastes.
The municipal solid waste (MSW) is usually a combination of household, agricultural, commercial and industrial wastes, especially in
The internationally accepted hierarchical approach to management of wastes is:
a) Waste avoidance / minimisation
b) Re-use and recycling (if it does not threaten public health safety and the environment).The biodegradable wastes are a good source for compost and biofuels. Resource recovery is also possible for non- biodegradable wastes if there are no constraints with regard to public health and the environment.
c) Treatment to destroy the hazardous components of the waste:
(i) Land treatment for biodegradable wastes (ii) Incineration- This is a treatment technology involving destruction of hazardous components of waste by controlled burning at high temperatures. The resulting non- burnable ash and other residue must be removed and transported to a final disposal site. (iii) Treatment of sewage- The treatment processes produce a liquid effluent and sewage sludge. The liquid effluent is discharged to natural waters subject to applicable standards and regulations. The sewage sludge can be used as a fertilizer on agricultural land (If it does not pose harm to health and the environment), otherwise it is incinerated.
d) Final disposal:
i) Engineered landfill – The open dumps create a nuisance by being unsightly, breeding pests, polluting the air, and polluting ground water and surface water. The engineered landfills (sanitary and secure) are designed to minimise the chance of release of leachate (hazardous liquid substances) into the environment. (ii) Ocean dumping or disposal at sea (subject to public health and environmental considerations).(iii) Deep-well disposal:- This entails disposing of waste by injection into deep wells, in the rock which is below and completely isolated from all fresh water aquifers, thereby circumventing contamination of water table. However, disposal of liquid waste in deep wells has been linked to increase in occurrences of earthquakes in seismically active areas. (iv) Concentrate and contain -This is used for wastes that defy known treatment methods.
2) Soil degradation / vegetation and biodiversity losses / deforestation / desertification.
Soil degradation is the loss of physical, chemical and biological properties of a soil, leading to decline in the soil nutrients and stability. Soil degradation may result in loss of vegetation cover, decline in water availability, erosion of top soil, etc.The degraded soil is the one that has lost its properties, rendering the soil unsuitable for cultivation, grazing and other activities.
Soil degradation can be prevented and/or reversed through the following approaches: Promoting effective soil and water conservation through proper land husbandry; Avoiding agriculture practices on marginal lands ; Encouraging the adoption of integrated crop and livestock farming systems; Increasing the productivity and sustainability of rain fed farming ;Controlling use of fertilizers , pesticides and herbicides through regulations and economic instruments; And promoting primary environmental care by farmers.
Deforestation is the indiscriminate felling of trees. The major causes of deforestation includes: Conversion of forest to building and other infrastructural facilities; Indiscriminate logging of timber and wood; Indiscriminate firewood extraction and gathering; Forest fires; Over- grazing by animals; etc. Desertification is the process whereby arid and semi-arid lands are converted to deserts, often by improper farming and pastoral practices. These situations can be reversed by adopting sustainable agro- forestry and afforestation practices.
Forests provide ecological services and benefits which include the following:
a) Stabilizing hydrological (water) cycle (b) Protecting soils by providing vegetation cover (c) Stabilizing climates (d) Conserving renewable resources (e) Preserving breeding stocks, population reservoirs and biodiversity (f) Providing non-timber and food products (NTFP) like fruits and medicinal herbs (g) Supporting tourism and recreation and (h) Providing facilities for research and education.
3) Erosion: This is the displacement of soil by natural agents such as water and wind. Soils without or with partial vegetation cover are prone to sheet erosion. The sheet erosion deteriorates into gully erosion. Sheet and gully erosion causes damage to farmland and infrastructural facilities (building, roads, railways, etc). The run-off arising from erosion also pollutes water bodies. Sheet/gully erosion can be mitigated by controlling bush burning, deforestation and other human activities that expose soil surface.
Coastal erosion is the gradual removal of land along the coast. It is caused by the action of wave. It leads to destruction of lives, properties, the environment and recreational facilities along the coast. It can be mitigated by erection of barriers that can reduce the power of wave along the coast.
4) Flooding: Flooding is the occurrence of excessive volume of water in areas not usually waterlogged. The flood may remain for hours or days. Flooding leads to loss of lives and wreaks havoc on properties and the environment. It is caused by improper physical planning, poor or blocked drainage systems and building on flood plains. Control measures include: proper channelisation of floods, proper urban planning and regular clearance of drainage channels.
5) Water Pollution: Threats to water resources include such contaminants as: agrochemical run-off, untreated sewage; untreated industrial and mining wastes, radioactive substances, oil spillage. Water pollution causes destruction of fisheries and other aquatic resources, water borne diseases and food chain poisoning. Water pollution can be controlled by making and enforcing appropriate standards and regulations concerning discharges into water bodies.
6) Atmospheric Pollution: The air-borne industrial pollution (including gas flaring) is responsible for the environmental hazards which include:
a) Direct effects from industrial pollutants, which include vision problems, nausea, stress, coughing, shortness of breath, limonia, bronchitis, emphysema, lung cancer, dizziness, headache, instantaneous death, etc.
b) Acid rain is caused by air pollutants (oxides of nitrogen and sulphur). The pH of natural rain is normally 5.6. In highly polluted areas, the pH may be as low as 2, producing acid rain. The effects of acid rain include damage to vegetation and forest, monuments, statute, painting, etc. Atmospheric pollution can be controlled with effective anti-pollution equipment.
7) Global Warming: The build – up of greenhouse gases (GHG) allows light from the sun’s rays to heat the earth but prevents a counterbalancing loss of heat, leading to a warmer earth. The greenhouse gases are methane, nitrous oxide, ozone, carbon dioxide, carbon monoxide, and halocarbons, among others. The effects of greenhouse phenomenon include: sea level rise; flooding in coastal arcas; impact on global climate change; drought and water shortage; and sea surface temperature rises which can spawn tropical cyclones, typhoons, hurricanes, etc. The effects of global warming can be controlled by minimising discharge of greenhouse gases into the atmosphere.
8) Stratospheric Ozone Depletion: The ozone layer in the stratosphere (approximately 25-35 km from the earth’s surface) is responsible for shielding certain wavelengths of high doses of ultraviolet (UV) radiations from reaching the earth’s surface. High doses of UV at these wavelengths can damage the human eye; cause skin cancers; reduce rates of plant growth; upset balance of ecosystems; and reduce immunity in humans (i.e. increasing the risks of diseases).
The Ozone depleting substances (ODS) include chlorofluorocarbons (CFC), hydrochlorofluorocarbons (HCFC), halons, tetrachlorocarbon (CCl4), methyl chloroform, methyl bromide, etc. These ODS are used as aerosols, sterilants, specialized solvents, refrigerants, in foams making, etc. The only mitigation measure in this regard is using substitutes that are non-zone depleting or less damaging.
9) Noise Pollution: Noise pollution simply constitutes unwanted sound in our environment. Noise, depending on the levels, can interfere with our communication, diminish our hearing, and affect our health and behaviour, and even lead to permanent loss of hearing. The major sources of noise pollution are outdoor musical instruments, generating sets and industrial equipment. The hazards associated with noise pollution can be prevented, minimised, or controlled by making and enforcing appropriate standards and regulations on noise levels, including use of personal protection equipment at workplaces.