In an unprecedented move, schools in Lahore were officially closed for a couple of days this month because of heavy smog that has noticeably settled in every crevice of the city.

Not only has the city's air quality touched hazardous levels with zero visibility to go along, there also seems to be an acrid smell of burnt garbage in the air. The all-too-familiar phenomenon has now become the 'fifth climate' of Lahore.

Currently, with an Air Quality Index (AQI) of 285, the state of Lahore's air has moved from 'hazardous' to 'very unhealthy', where it remains the most polluted urban centre in Pakistan in terms of air quality.

But this isn't the first year of Lahore's suffering. For the past several years, the onset of the cooler months of October and November has been bringing with it choking smog to the city that heralds in respiratory illnesses, eye diseases, and particulate matter — tiny solid particles that we breathe and that poison our bodies. And while the long-term health impact of all this outdoor air pollution remains to be fully seen, the World Health Organisation says that the impact is likely to include increased risk of stroke, lung cancer, as well as heart disease.

How the changing dynamics of air movement contribute to smog

Historically, severe smog events have usually been accompanied by a strong temperature inversion. A temperature inversion refers to an increase in temperature with height and it prevents the normal upward movement of air or convection; thus acting as a “lid” trapping pollutants near the surface.

Overnight during the winters, air adjacent to the ground surface rapidly cools thus causing the surrounding air to cool down as well. This results in a layer of warm air at a higher altitude trapping the layer of cool air (adjacent to the ground) underneath it, keeping air pollution such as smog trapped. This scenario is exacerbated in cool weather, early mornings, and late nights.

Meanwhile, poor air quality usually occurs over a spell of several days, during which peak concentrations of one or more pollutants reach critically high levels. Although weather conditions do cause air pollution to build up, it is ultimately human activities that are the culprit behind excessive pollutant emissions.

Population growth is at the heart of the global pollution challenge

As nations struggle to provide energy, food, water, sanitation, housing, transportation, and other resources to ever-increasing populations, vast amounts of air pollutants are released into the atmosphere every year.

Growing metropolises in developing nations, many of whom have weak economies, rarely have access to economic and technical resources required to cope with, let alone reduce, emissions causing air pollution.

Also read: The crisis of air quality in Lahore

A minimal investment in pollution control equipment and a dependence on cheap but inefficient and highly polluting fuels, including coal, are worsening air quality around the world, particularly in South Asia.

In recent years, the growing number of vehicles relying on internal combustion engines in developing nations, combined with low quality fuels, such as fuel with high Sulphur content, weak environmental legislation, inefficient implementation of global emission standards, poor vehicle maintenance and efficiency, and poorly maintained roads are all links in the chain of ever-increasing air pollution.

Even where cars are more fuel-efficient, the rising number of vehicles and the longer distances they are being driven over outweigh the benefits of improved technology such as catalytic converters. These are devices incorporated in the exhaust system of a motor vehicle, containing a catalyst for converting pollutant gases into less harmful ones.

On top of that, vehicle engines operate less efficiently in a cold environment, and catalytic converters may take some time to reach their operating temperature from a cold start — in the meantime, exhaust emissions are uncontrolled.

As urban areas continue to expand, the distance that commuters have to travel on a daily basis also goes up. According to the UNDP, Pakistan is the most urbanised country in South Asia, and it is estimated that nearly half of the country’s residents will live in cities by 2025. So with urban centres in Pakistan continuing to swell with people, traffic, and industrial and commercial activities, the air quality is likely to deteriorate further in years to come.

More on this: Study identifies relationship between smog and rice residue burning in Punjab

Beyond the poorly maintained two-, three-, and four-wheeled vehicles that exceed recommended exhaust emission standards, industrial emissions from setups in residential areas and surrounding localities continue to spew out hazardous chemicals into the air.

To top this off, every year, as the new sowing season sets in, farmers burn remnants of the previous crop or parali, which further compounds the problem.

This is not only a Pakistan problem though. Massive crop-burning in India each year is not only contributing to air pollution there but that pollution is also carried across to Pakistan due to seasonal shift in winds.

Understanding 'particulate matter'

The principal pollutants of concern are Sulphates and Sulphur-based oxidation products, suspended particulates or 'particulate matter', carbon monoxide, volatile organic compounds, and toxic chemicals.

The US Environmental Protection Agency describes Particulate Matter (PM) as a mixture of solid and liquid droplets in the air, which include dust, dirt, soot, and smoke.

These particles vary widely in size, with some being so small they can only be seen under an electron microscope, and others are visible to the naked eye.

Particulate Matter is generally classified into two categories based on their sizes in micrometres; PM10 and PM2.5. For perspective, PM2.5 particles will be 30 times smaller than the width of a single human hair. The small size of PM2.5 is a cause for concern, as these particles can be embedded deep in our lungs and even enter the bloodstream, thereby affecting other organs.

Throughout Asia, concentrations of particulate matter are much higher than the globally accepted limits. A study conducted in Lahore over a five-year period found that particulate matter concentrations were on average 14 times higher there than the limit prescribed in WHO guidelines.

Explore: Amnesty International says every person in Lahore at risk due to smog, urges 'urgent action'

Given that only 1% of the country’s industrial establishments report emissions and only one refinery in Pakistan produces fuel according to global standards, distressing concerns over the government’s neglectful conduct with respect to air quality are bound to emerge.

Over to the East, a public health emergency has been declared in New Delhi — work on construction sites has been halted, the number of vehicles on roads is being limited, and five million schoolchildren are being given face masks by the government.

A public health concern

Smog and other forms of air pollution have been directly and indirectly linked with rising fatalities and the onset of diseases such as asthma, respiratory tract infections, eye infections, allergies, and interlinked cardiac and pulmonary pathologies leading to premature death. Already, higher levels of blood pressure have been reported in Lahore’s schoolchildren.

Nine out of 10 people on earth breathe polluted air, the WHO says. As a result, seven million lose their lives every year. The international body also reports that the health effects of breathing polluted air are “equivalent to that of smoking tobacco.”

What makes air pollution a particularly difficult public health challenge is the fact that you cannot always escape it. No matter what locality you live in, be it the lush green suburbs emerging on the outskirts of our cities, or a densely populated city centre — air pollution carries over and spills across.

An active person breathes in between 10,000 to 20,000 litres of air every day, which comes down to between seven and 14 litres per minute. This intake varies with the level of physical activity and age. During inhalation, pollutants that are suspended in the air are also drawn into the lungs; from where they may enter the bloodstream, taking up permanent residence in critical organs making up the cardiovascular system.

The impact of these pollutants ranges from mild irritation to immediate (acute) and long-term (chronic) disease to premature death, based on a variety of factors including nature of pollutants, exposure duration, and the state of existing health.

As WHO Director of Public Health Dr Maria Neira aptly puts it: “The true cost of climate change is felt in our hospitals and in our lungs.”

We need to act now before we are choked out.

Header image: Smoke rises from a steel mill in Lahore causing pollution in 2018. — A. M. Syed

Are you solving Pakistan's environmental and climate-related challenges? Share your insights with us at prism@dawn.com