Why is Nagpur repeatedly – and wrongly ?!- tagged as a ‘city with acid rains?’ Is this a conspiracy to keep industries away?

First of all what is ‘Acid rain?’

Clean water, is neutral, i.e. it is neither acidic nor alkaline having a pH value of 7. When rain falls over a city that does not have much atmospheric pollution we expect rain water too, to be neutral.

Acid rain on the other hand is rain water with high acidic value. When pH value of water goes below 5.65 it is considered ‘acidic’.

This is what wikipedia says about it – Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions (low pH). It can have harmful effects on plants, aquatic animals and infrastructure. Acid rain is caused by emissions of sulfur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids. Acid rain has been shown to have adverse impacts on forests, freshwaters and soils, killing insect and aquatic life-forms, causing paint to peel, corrosion of steel structures such as bridges, and weathering of stone buildings and statues as well as having impacts on human health.

The first time historically that scientists noticed Acid Rain was over London at the height of the industrial revolution when most energy was produced by burning coal – coal was burnt in homes and buildings too to keep them warm in winters.

Thus Nagpurians were shocked and surprised when some leading newspapers of the city reported a ‘finding’ by Government labs based in Pune and published in the Journal of Atmospheric Chemistry that stated that Nagpur was one of the few cities of the country that had Acid Rains.

Not just that, the situation was said to have worsened badly over the last 2-3 decades with acidity increasing alarmingly.

Some independent scientists of the city, such as Kaustuv Chaterjee running Green vigil and his colleagues were full of disbelief at the report and were not ready to accept it at face value.

They knew Acid rains is formed when atmospheric SO2 and Nitrogen oxides presence is very high. Water reacts with these chemicals to form acids which make rain water acidic too.

They were also aware, and had data to prove it that these emissions, SO2 and Nitrogen oxides, are well within the permissible limits in tests after tests conducted by the Maharashtra Pollution Board. Then how could rain water over Nagpur turn acidic?

Also, if rains had been acidic there would have been other obvious symptoms too. Animals and plant life would have suffered, even human beings getting wet during monsoons would have had boils and eruptions on their skin. Buildings would have paint peeling off and metal in bridges and other structures would have rusted.


Yes, but when a city’s rainfall is said to be acidic, one effect will definitely happen – INDUSTRIES WOULD STAY AWAY!! Why would they want and go and set up industries in a city that was already highly polluted and face more severe restrictions on their effluents treatment etc.? Pollution Board is one govt. body industries are as it is wary of the most!!

So Kaustav wrote to the scientists concerned asking for explanation and giving data available with them.

They received a reply that did not disagree with findings of SO2 and Nitrogen oxides being low. But their explanation for the supposed ‘acid rain’ was rather defensive and circumstantial. This is what they wrote –

It is to mention that even the SO2 & NOx emissions within the permissible limits can also lead to low pH as these are not the only controlling factors.

Clouds formed over a location are driven by winds and during their traverse, it may encounter with other clouds formed over neighbouring locations and get mixed. Rainout and washout of the pollutants associated with rain over a location therefore do not reflects the pollutants exactly over that location, but represents scenario of surroundings. It depends on many factors which are not attempted in the paper under question.

It is to clarity that above mentioned studies by IMD scientists are based on data from a single raingauge station located in respective IMD offices. For Nagpur the raingauge station is located at IMD office, Near Airport, Nagpur.

So, the scientists collected rain from a single station, for supposedly ONE RAIN FALL, and jumped to the conclusion that Nagpur has acid rain falls!

And why pray, repeated studies in Nagpur and not other industrial cities of the state like Aurangabad, Nasik or Pune? Because Nagpur has an IMD office!!

Also there are reports from previous studies to go by… which also must have been based on faulty premise.

When repeatedly such reports are being published and ‘national media’ carry them, imagine what it does to a city’s reputation?

Makes us wonder – is this deliberate or just mere co incidence that Nagpur is targeted like this? When there are hardly any industries here, except one thermal power station far away from the airport and comparatively less of cars and traffic!!

Is it a case of – give the dog a bad name and kill it??


—Sunita Mudaliar (Associate Editor)