KAR ACHI: Past week, amid a dust storm, the city was hit by an unpleasant stench, which worsened over the weekend, especially in areas close to the sea.

The odour was particularly strong in Clifton, DHA, SMCHS, PECHS, Korangi, Orangi, North Nazimabad, Federal B Area (blocks 9 and 10), and also noticeable in Saddar.

`The smell was unbearable and aggravated my sinusitis. I`ve had breathing issues for years, but this October, my symptoms have worsened, and I believe it`s due to the city`s changing climate,` shared Haris, a 26-year-old corporate employee who lives in SMCHS.

`I`ve been commuting through Clifton Block 3 for at least five years, and around this time of year, there is usually a foul odour, but it typically lasts no more than 48 hours. However, this time, I had difficulty breathing, even though I have no history of respiratory issues,` said Faizan, who commutes daily from F.B Area Block 9 to Clifton.

When contacted by Dawn, Muhammad Moazzam Khan, technical adviser at the World Wide Fund for Nature ( W W FP a k i s t a n ), explained that the odour was caused by decomposing phytoplankton, sea plants that grow underwater, and was linked to changes in air direction.

`Karachi is situated near the Northern Arabian Sea, where monsoon reversal and circulation occur,` he explained.

`The monsoon season lasts from mid-May to mid-September, and once it ends, turbidity in the water increases.

`Phytoplankton thrive in specific temperature conditions,` he added.

`During the monsoon season, limited light prevents their growth, causing them to form a balloon-like mass that`s then carried by the wind.

Rafiullah, an ecologist, explained the situation in terms of photosynthesis and rising temperatures in Karachi.

`Phytoplankton perform photosynthesis and release oxygen into the atmosphere, while zooplankton, from the animal kingdom, float alongside them. Both groups have cycles of growth and decline,` he said.

He added, `A significant number of plankton end up in elevated areas due to tidal action. When the water recedes, they dry up, releasing a foul odour. The situation worsens when lowpressure systems occur, reducing air circulation and intensifying the smell.

When asked if the foul odour, combined with the dry weather and dusty winds in mid-October, could pose health risks, he stated that while there`s no `concrete` evidence yet, the rapid temperature changes could potentiallylead toissues. `Prolonged exposure might affect sinusitis,` he noted.

Yasir Darya, CEO of Climate Action Centre (CAC), echoed a similar view but highlighted the impact of air quality and rising temperatures on health.

`The city`s air quality has deteriorated significantly in recent years, and exposure to any foul odour could lead to various health issues,` he explained. He added, `Besides phytoplankton, rottingfish in the sea is also a major health hazard, as it harbours bacteria, microbes, and viruses that carry infectious diseases.

Currently, the temperature in the city ranges from 28°C to 34°C on an average, accompanied by extreme dryness, while night-time temperatures drop to 21°C.

The probability of a muggy day in Karachi decreases significantly throughout October, falling from 84 per cent at the beginning of the month to 37pc by its end.

In October 2023, Karachi recorded 10 sunny days, eight cloudy days, and no rainy days. The average maximum temperature was 33°C, with a high of 37°C and a low of 30°C. The average humidity was 78pc, reaching a maximum of 100% and a minimum of 36pc. The slight fluctuations in temperatures over the years are not only impacting the Air Quality Index (AQI), but the decrease in humidity may intensify the odour, potentially leadingtohealthhazards.