Dust fall is no act of God

Since June 12, a large part of Northern India has been engulfed in a massive haze of dust. Weather scientists from the India Meteorological Department (IMD) say that an aggressive, westerly wind blowing at a speed of 40-50 km over a vast expanse of Punjab, Haryana, Rajasthan, Delhi, the plains of Uttarakhand and Western Uttar Pradesh is picking up the huge swathe of dust. 

Due to the suspension of dust, visibility is low and airborne particles have crossed the danger mark in Delhi and the surrounding region. The current phenomenon is different from the localised dust and thunder storm combination or aandhi that typically characterise the Indian summer, especially in Northern India. 

This time, a prolonged dry spell and surprising trends in westerly winds have created this regional haze. The weather scientists say that this dust veil may get lifted in a couple of days with the weakening of wind and chances of rain. But the dust haze in Delhi has already led to a hue and cry and the question on everybody’s mind is: how dangerous is this phenomenon?

Online air quality monitors are already beeping danger as the larger particle size of 10 micron (PM10) that are highly impacted by dust, show an increase eight to nine times over the permissible level. The data from 19 air quality monitoring stations of Delhi shows a sudden spike in particulate levels during the dust storm days.  

In response to the current crisis and as part of the Graded Response Action Plan, the Environment Pollution Control (Prevention and Control) Authority has already sent out an advisory to curtail construction activities, shut down hot mix plants and organised sprinkling. The Lt Governor on Thursday ordered that all civil construction activities in Delhi be stopped from June 16. The Haryana government has initiated closure of construction and hot mix plants among others in the NCR region.

So what is this summer pollution all about?
Every year, the summer season traps heat and dust in the Northern Indian region. Summer pollution is very different from winter pollution when lack of wind, low temperature and inversion trap pollution inside the city. 

The IITK study mentions that air is more toxic in winter than in summer as it contains a much larger contribution of combustion products in the former than in the latter. It warns that in summer, to improve air quality, we need effective control solutions for soil and road dust, fly ash re-suspension and solid waste burning. Yet, it is important to understand the risk from summer dust to protect public health.

Simply put, the yellow-brown dust is an odd mix of natural erosion of soil, sand and rock mixed with pollen, microscopic organisms, plant material and dander. Wind-blown dust from deserts, digging activities, and re-suspension of road dust, all add up to create the dust haze. Relatively bigger particles fall out of the air quickly and fairly close to where it got lifted but smaller particles remain airborne for a longer period of time.

Normally, in its pristine nature, dust is not considered that toxic and is seen as a respiratory irritant. But what makes dust deadly is the way it accumulates toxic substances from other combustion sources including vehicles, industry, solid waste and biomass burning in urban environments. Countless dust particles in the air offer a huge surface area for other deadly substances to cling on and dust becomes the carrier of toxic stuff. 

Coarse dust particles are usually trapped and filtered by our nose and mouth and are not considered as dangerous as the tinier ones that go deep inside the lungs and mix with the blood stream. Coarse dust is a respiratory irritant. It causes irritation of the eyes, coughing, sneezing, asthma attacks and worsens symptoms of chronic obstructive airways disease (COAD) or emphysema. Infants, young children and elderly people are particularly vulnerable.

Global studies have shown that heavy dust events are associated with an increased risk of hospitalizations for asthma. Even desert dust particles that move around the globe cause inflammatory responses in the airways. 

The current situation in Delhi and the NCR warrants emergency action under the Graded Response Action Plan. Even though a lot of dust is coming from outside, local sources of dust in the urban environment are also enormous. This dust event is also a lesson for long-term action. 

Learn from Africa. The “Great Green Wall” initiative is creating a barrier of vegetation in vulnerable areas across the continent. This is expected to be 4,000-mile wall of trees stretching across the Sahel, from Senegal to Djibouti. 

It will be dangerous to ignore this problem of dust as an act of God. Make all dust generating activities—from digging of roads to construction, accountable, and initiate massive afforestation. Act now. 

By: Anumita Roychowdhury  
(downtoearth.org.in)