The sheer beauty of Kathmandu – the cultural city of temples with more UNESCO world heritage sites than any other cities in the world – would stun anyone that visits. Nepal’s capital also has a different, darker side that leaves you gasping. The reason isn’t because of its breathtaking beauty but because of the breath taking quality of air in the city.
Kathmandu’s poor air quality has received much attention recently after it became the biggest killer in Nepal. Yet the quality of the air in the valley keeps deteriorating every year. This is of course not just a story of Kathmandu; other large industrial cities face a similar problem too. Air pollution is a major cause of death across the world. It claims over three million lives each year surpassing malaria and HIV/AIDS.
Breaking down air pollution
Air may be contaminated by a range of different solid and liquid particles including, smoke, dust, aerosols and pollens. A sum of measurements of all these pollution particles is known as particulate matter (PM). Air quality is usually measured by air stations that record the amount of PM in the atmosphere.
When we breathe in, our body prevents most pollution particles from reaching the lungs. The nose acts as an initial filter; mucus in our throat and respiratory tracks also trap pollution particles. Despite our body’s best attempt, extremely tiny particles that are smaller than 10 micrometres can bypass these traps and enter the lungs to pose danger to human health.
Coarse particles (PM10), sizing from 2.5-10 micrometres, are usually a product of dust or pollens. They might cause irritation to eyes, nose and throat. Fine particles are less than 2.5 micrometres (PM2.5). They’re produced by combustion, including smoke generated by industries and motor engines. These particles are so small; they’re only visible by high-resolution microscopes, so they still linger in, what seems like “clean air”. PM2.5 particles can enter and settle deep into our lungs, and may enter the bloodstream to reach other organs. For example, toxic pollution particles – produced by engine combustion – that are linked to Alzheimer’s disease have been found in the human brain.
Air pollution: a double-edged sword
Industrial produce, transport and infrastructure development are all required to meet the demands of large urban cities. These things generate a lot of pollution particles. So, on a current system, pollution level will keep on rising as the city gets larger. Taking these into account, it’s our responsibility to find different ways to make our cities environmentally sustainable.
Household and commercial emissions – principally generated by wood and coal burning for cooking and heating – accounts for one-third of total deaths caused by air pollution. This is especially high (reaching up to 70%) in densely populated parts of Asia. A number of European nations now aim to phase coal out in the near future; a similar attempt to remove coal from Asian markets would save hundreds of thousands of lives. It doesn’t look realistic right now as 40% global electricity is generated by coal-fuelled power plants.
Investing in renewable energy technologies such as solar panels, wind turbines and hydropower will no doubt alleviate the need for energy generated by coal burning. Many developing countries contain abundant natural sources of renewable energy. Despite this, they haven’t been able to fully exploit these sources to generate energy. That’s partly why residential and commercial energy use generates large-scale emission in these regions.
Walking or cycling schemes incentivised by workplaces and the authorities also help reduce particle pollution. These schemes are unlikely to be successful in cities in the developing world because of poor infrastructure, including a lack of paved footways and safe cycle lanes. A big irony in heavily polluted cities is that most prefer to take the bus or a car for intercity travel to avoid outdoor air pollution. In such cases, using electric cars would reduce the toxic nitrogen and sulphur emissions generated by cars that run on petroleum products. The catch is that a large portion of electricity is generated by burning coal, which produces, even more, particle pollution.
Kerbing air pollution
There are a few incidents where cities have managed to kerb the level of particle pollution and increase air quality. In one such instance, moss played a key role in pollution control. These humble plants are rootless, so they use their bodies to absorb nutrients and water from the atmosphere. Mosses can intake particle pollutions present in the air as they are highly adsorbent. Using this to advantage – in the USA city of Portland – mosses were gathered from several areas to map particle pollution levels in different regions. This helped to identify the source of toxic heavy metals in the air and appropriate actions were taken to bring this under control.
Rajshahi, a city in Bangladesh, is exemplary in the way it has tackled air pollution. PM10 particles in the city have decreased by nearly 70% from 2014 to 2016. The city reduced traffic-generated emissions by importing battery-powered rickshaws and turning them into the main form of public transport. Pollution levels were further reduced by upgrading brick kilns, cleaning chimneys and using cleaner fuels.
Dust particles are major contributors of PM10 pollution. In the developing world, PM10 levels are especially high due to a combination of factors, including unpaved roads and footways, and poor roadside drainage system. Paving is the most effective way of reducing dust pollution but it’s also highly expensive and requires regular maintenance. The cost of paving roads is much higher in countries that are conflict-ridden or have a high level of corruption. Increasing soil moisture by spreading gravel on unpaved roads, and planting trees and grasses in barren, exposed areas also help to control dust pollution. Rajshahi’s success in ridding dust pollution from the city was greatly aided by employing a “zero-soil” policy, which aimed to leave no exposed land in the city.
Vehicles driving on non-paved roads carry dust when they enter the paved region. The Wind also blows soil from uncovered regions on the roadside, which gets further blown in the air from vehicles. This problem escalates further when the rain washes soil onto the road. A good roadside drainage system would drain the roadside soil to leave the city clean. And a lack of a roadside drainage system forms large puddles of muddy water leaving more dust behind when they dry. So, even paving all roads and footways can leave a large amount of dust in the city without a proper drainage system.
Taken everything together, it’s possible to control air pollution and still meet the demands of thriving industrial cities. For this to happen, we need emission-free transportation, proper city planning and clean energy.