Environmental pollution
Over the last three decades there has been increasing global concern over the public health impacts attributed to environmental pollution, in particular, the global burden of disease. The World Health Organization (WHO) estimates that about a quarter of the diseases facing mankind today occur due to prolonged exposure to environmental pollution. Most of these environment-related diseases are however not easily detected and may be acquired during childhood and manifested later in adulthood.[ ]
Improper management of solid waste is one of the main causes of environmental pollution and degradation in many cities, especially in developing countries. Many of these cities lack solid waste regulations and proper disposal facilities, including for harmful waste. Such waste may be infectious, toxic or radioactive.
Municipal waste dumping sites are designated places set aside for waste disposal. Depending on a city’s level of waste management, such waste may be dumped in an uncontrolled manner, segregated for recycling purposes, or simply burnt. Poor waste management poses a great challenge to the well-being of city residents, particularly those living adjacent the dumpsites due to the potential of the waste to pollute water, food sources, land, air and vegetation. The poor disposal and handling of waste thus leads to environmental degradation and destruction of the ecosystem.
In 1950, Minamata bay tragedy caught the world unawares. It has been since recognized that the multiple pathways of mercury contamination through air, water, food, pharmaceuticals, cosmetic products, etc., pose serious concern because it persists in the environment and accumulates in the food web. Amongst three forms of mercury, the organic form is most toxic as it passes the blood brain barrier owing to its lipid solubility. The damage has vast implications with human beings at the top of food chain getting worst of the deal owing to biomagnifications. This review was written to focus on recent researches showing adverse health effects of low doses of mercury, to instigate the requirement for a new era of pharmaceutical development and to create further awareness regarding environmental remediation.
Sources of mercury
Mercury in air
As a natural element mercury is ubiquitous in the environment, approximately 10,000 tons originates from degassing of earth’s crust, to this amount approximately 20,000 tons/year is added by anthropogenic activity[]. Mercury emissions from thecoal smoke is the main source of anthropogenic dischargeand mercury pollution in atmosphere. It is estimated thatthe mercury emissions will increase at a rate of 5% a year []. When medical devices like thermometer/sphygmomanometer or household items like fluorescent night lamps or thermostats are discarded residual mercury is emitted. The US Environmental Protection Agency (EPA) National Emissions Inventory (NEI) had the most complete coverage for all states. It found coal-fired electric utilities accounted for 52.7% of the region’s Hg emissions. Other important contributors to regional emissions included municipal waste combustion (5.6%), mercury-cell chlor-alkali plants and hazardous-waste incinerators (4% each), stationary internal combustion engines (ICEs) (3.5%), industrial, commercial and institutional (ICI) boilers (3.3%) and lime manufacturing (3.0%) and medical waste incineration (1%) []. Informal gold mining has used mercury since antiquity. High contamination of Brazilian Amazon (Brazil is world’s second largest producer of gold) is indicated by the strong presence of mercury in its biota []. It is an occupational hazard for dental staff (Rowland and Baird, 1994), chloralkali factory workers (Barregard and Lindstedt, 1994) goldminers (Grandjeanet al., 1999), etc.
Mercury in water
Mercury in air eventually passes into rivers, lakes and oceans after travelling long distances together with wind. With mercury contaminating rain (Domagalski et al., 2004;Levine, 2004), ground and seawater (Beldowski and Pempkowiak, 2003), no one is safe. Cloud water was collected during nine non-precipitating cloud events on Mt. Mansfield, VT in the northeastern USA between 1 August and 31 October, 1998. Mercury cloud water concentrations ranged from 7.5 to 71.8 ng l (−1), with a mean of 24.8 ng l (−1). Liquid water content explained about 60% of the variability in Hg cloud concentrations (Malcolm et al., 2003). There are also linkages between acidic deposition and fish mercury contamination and eutrophication of estuaries (Driscoll et al., 2003). Numerous factories that directly pump untreated effluents pollute groundwater. The polluted water produces acidic rain which ultimately contaminates all water bodies. Report published in a reputed Indian daily, The Hindustan Times showed result of water samples analyzed at IIT, Kanpur. Groundwater samples in India from eight places each from Punjab, Haryana, Andhra Pradesh, Gujarat and Kanpur showed surprisingly high levels of Hg in all samples. Water sample from Panipat (Haryana) had highest level of Hg at concentration 268 times that of safe limit, even the sample with least Hg value had 58 times more mercury than the upper safe limit (Hindustan times, 1999). Algal bloom and leaf fall events can result in elevated methylmercury (MeHg) concentrations in surface waters, potentially leading to increased MeHg accumulation in fish (Balogh et al., 2002).
Mercury contamination of food
• Food of animal origin
The emitted mercury both natural and anthropogenic is in
an inorganic form predominantly metallic vapour, which is
carried off to great distances by winds and eventually falls in
water bodies. In aquatic environments, inorganic mercury is
microbiologically transformed into lipophilic organic compound, methylmercury. This transformation makes mercury
more prone to biomagnification in food chains. Consequently,
populations with traditionally high dietary intake of food
originating from fresh or marine environment have highest
dietary exposure to Hg. Extensive research done on locals
across the globe have already established this for instance polar Eskimos. Persons who routinely consume fish or a particular species of fish are at an increased risk of methylmercury
poisoning (Table 1)(Hansen and Dasher, 1997). Since mercury intake is expressed on a per kilogram body weight basis
exposure of children under age 14 is two–three times high because of higher food intake per kilogram body weight. After
measuring total mercury in the edible portions of 244 selected
fish and shellfish purchased in Canada at the retail level, the
Canadian advisory to children and women of child-bearing
Environmental Pollutants
• Heavy Metals e.g., lead, mercury, cadmium, arsenic, chromium, zinc, nickel and copper
• Persistent Organic Pollutants e.g., aldrin, dieldrin, dichlorodiphenyl-trichloroethane (DDT), endrin, heptachlor, toxaphene, chlordane, hexachlorobenzene, mirex (organochlorines, organophosphates, carbamates) and polychlorinated biphenyls (PCBs)