KARACHI is the largest city of Pakistan and it is also one of the top air polluted cities in the world according to the 2014 World Health Organisation report, and, sadly, we just don’t seem to do anything in this regard.

The WHO report ranked cities after studying their air for the presence of harmful gases, such as nitrogen dioxide, carbon monoxide and sulphur dioxide, besides small airborne particles 10 and 2.5. Particulate matter is among the most detrimental of these pollutants. Studies link it with increased rates of chronic bronchitis, lung cancer and heart disease.

It is determined that particles smaller than 10 micrometres in diameter pose the greatest threat to human health, as they not only get deep into a person’s lungs but can also enter the blood stream. Therefore, the WHO advises that fine particles of less than 2.5 micrometres in diameter should not exceed 10 micrograms per cubic metre.

The report further revealed that 13 of the 20 most polluted cities in the world are in India, with New Delhi at the top having 153 micrograms of PM2.5 per cubic metre; while three were from Pakistan. Karachi had 117 micrograms of PM2.5 per cubic metre, Peshawar had 111 micrograms, and Rawalpindi had 107 micrograms.

Whether it is noise, chemical, radioactive, thermal, light, visual or soil pollution, all of these impose disastrous impact on the natural world, on the health of human beings and all living things in their own unique way. The bottom line is that the safety and health of the present and future generations are at risk and it’s time to wake up to the problem and do something to resolve it.

Today we will have a quick glance at some of the highly toxic cities around the world.

North Pacific Gyre

ALSO known as the Pacific Trash Vortex. This is an extensive area in the North Pacific containing high levels of microscopic toxins, plastics and chemical sludge. As a result of the rotating Pacific currents (known as gyres in oceanography) these have been “trapped” in the region. It is extremely damaging to the marine environment.

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IT is considered the industrial wasteland. Though a lot of the factories are not operating anymore, the pollutants they emitted before they were shut down are still present in the air. On top of it all, no one is willing to take responsibility for the 120,000 tonnes of toxic emissions that continue to plague the city.

Matanza-Riachuelo, Argentina

THE Riachuelo Basin is a waterway whose name is synonymous with pollution. More than 3,500 factories operate along the banks of the river, numerous illegal sewage pipes running directly into the river, and there are 42 open garbage dumps as well.

An estimated 15,000 industries actively release effluent into the Matanza-Riachuelo river basin. A 2008 study found that soil on the banks of the river contained levels of zinc, lead, copper, nickel and chromium that were all above recommended values. About 60 per cent of the 20,000 people who reside near the river basin live in territory that has been deemed unsuitable for human habitation, leading to higher levels of diarrheal diseases, respiratory illnesses and cancer. It doesn’t help that residents have few sources of drinking water, leaving them dependent on the polluted river. The problem is improving, however, thanks in part to a billion-dollar World Bank-funded effort.

Tianying, China

THE major culprit behind the pollution problem in this city is lead, along with a number of other heavy metals. Tianying is situated in the north-eastern region of the country; it is a highly industrialised but unfortunately, has poor policies and uses nomadic technology. Its previously fertile soils are now steeped in lead, and its inhabitants are at great risk for developing lead-associated health problems. These illnesses can be anything from irritability to dullness, to hallucinations, and even to memory loss.

Linfen, China

WITH approximately three million of its residents affected by pollution, Linfen is situated at the centre of the country’s coal belt. The hills surrounding the city are peppered with tonnes of coal mines. One simply can’t sniff the air without smelling the odour of burning coal.

It has been declared by the country’s State Environmental Protection Agency as having the worst air in China. And if you are still not convinced, go there and hang your laundry out, it will be black before it can even dry. Wanna try?

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THERE are 270 registered tanneries in Bangladesh, and around 90-95 per cent are located at Hazaribagh on about 25 hectares of land. The process of making leather uses dangerous amounts of the chemical hexavalent chromium which causes cancer and is almost universally banned throughout Europe, but it is among the 22,000 cubic litres of toxic waste dumped into Hazaribagh’s water supply every day.

Tannery workers’ homes are built next to contaminated streams, ponds and canals and they suffer horrifying symptoms including skin rashes, acid burns, dizziness and nausea which result from repeated exposure to hazardous chemicals when measuring and mixing them as part of the tanning process.

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THERE is actually a carpet of junk over the river Citarum —the largest river in Indonesia; it supports more than 30 million residents who rely on the water source for agricultural, domestic and personal use. However, unregulated factory growth since the area’s rapid industrialisation in the 1980s has choked the Citarum with both human and industrial waste. The river is now known as one of the most polluted in the world.

Over 200 textile factories line the river banks. The dyes and chemicals used in the industrial process — lead, arsenic and mercury amongst them — are churned into the water, changing its colour and lending the area an acrid odour. Plastic, packaging and other detritus floats in the scummy water, rendering the river’s surface invisible beneath its carpet of junk.

Even then it provides 80 per cent of Jakarta’s drinking water with lead more than 1,000 times the recommended level and manganese at four times the recommended level.

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THE nuclear plant disaster of 1986 led to the city being considered as uninhabitable, particularly the 19-mile exclusion zone that surrounds the plant. Although an enormous amount of radiation was released during the disaster, most of the radioactivity has remained trapped within the plant itself.

Some estimate that more than 100 tonnes of uranium and other radioactive products, such as plutonium, could be released if there is another accident.

From 1992 to 2002 in Belarus, Russia, and Ukraine more than 4000 cases of thyroid cancer were diagnosed among children and adolescents, those under 14 years were most severely affected. More than five million people currently inhabit the affected areas of Belarus, Russia, and Ukraine, which have all been classified as ‘contaminated’ with radionuclides credited to the Chernobyl accident. Skin lesions, respiratory ailments, infertility and birth defects were the norm for years following the accident.

Dzerzhinsk, Russia

IN the years between 1930 and 1998, over 300,000 tonnes of chemical wastes were dumped in Dzerzhinsk. It is named as the world’s most chemically polluted city by the Guinness Book of World Records.

The average life expectancy in this Russian city is quite low. Men usually die at the age of 42, while women don’t live much longer than 47. There might be plenty of reasons behind this, but the general agreement is that the highly toxic pollutants found in the city might have something to do with people dying too early.

Norilsk, RussiaCan you guess how much zinc, arsenic, lead, cadmium, selenium, nickel and copper is released yearly into the air of Norilsk? Well, there’s no accurate reading, but it’s estimated to be over four million tonnes! This Russian city has the world’s biggest heavy metal smelting complex, and you can probably guess that this is the cause of the ridiculously high number of city dwellers who die from respiratory illnesses.

If you need further proof that Norilsk is a massive wasteland, you only need to look at the 30-mile area around the nickel smelter. You won’t find even one living tree!

Kabwe, Zambia

IN 1902, rich deposits of zinc and lead were discovered in Kabwe. Mining and smelting commenced soon after and ran almost continuously until 1994 without addressing the potential dangers of lead contamination. The mine and smelter are no longer operating but have left a city poisoned by debilitating concentrations of lead dust in the soil and by metals in the water.

In one study, the dispersal in soils of lead, cadmium, copper and zinc extended over a 20 km radius at levels much higher than those recommended by the World Health Organisation.

Vapi, India

AS home to a huge portion of the nation’s industries, Vapi is a city whose waters and lands are highly contaminated with harmful chemicals and metals. Its groundwater reportedly contains mercury, the level of which is 96 times higher than what’s considered safe by the World Health Organisation. Repeated exposure to mercury over a long period of time can lead to scores of medical conditions such as muscle weakness, impaired peripheral vision and other neurological deficits, to cite a few examples.

Yamuna River, India

AS the largest tributary of the Ganges, scientists estimate that roughly 60 per cent of Delhi’s waste gets dumped into this river. And this doesn’t change the fact that millions of Indians still rely on these murky, sewage-filled waters for washing, waste disposal, bathing and even for drinking.

Sukinda, India

AS much as 97 per cent of India’s chromium supply comes from this city, leading to a 30-million-tonne pile of mining waste that literally form mountains. Hexavalent chromium, which is a known and potent cancer-causing substance, can be found plentiful in nearby waters. It is believed that exposure to the air, soil and waters near the city’s mines have caused different types of cancer to an estimated 2.6 million people.