Air pollution in India is not just responsible for making the air toxic— because it’s also turning our rain acidic. So, what’s happening to the rain? How is it becoming acidic? The answer is that air pollution causing acid rain in India means a double attack for everyone. Acid rain occurs when the pH level of rainwater drops below 5.6. According to a recent study, India can experience instances of acid rain due to high AQI levels (air quality index).
Let’s dive into how air pollution is turning rain acidic and why this is becoming a serious threat to everyone. A recent case study by the Indian Meteorological Department (IMD) and the Indian Institute of Tropical Meteorology (IITM) has revealed some critical insights. The study, based on data collected over the past 34 years. Hence, it shows a rising trend of acid rain in the country. Air pollution is a key contributor to this growing problem, as mentioned in the study.
In this blog, you’ll understand what acid rain really is, why it’s harmful to both the environment and human health, and how its occurrence has grown in India over the last three decades. We’ll also break down what the IMD study says and what this means coming from an official Indian government authority.
What is Acid Rain, and How Does Air Pollution Increase It?
Rain is a vital part of the water cycle and is essential for life. But what happens when rain becomes acidic? It means our lives are at risk—not just from drinking water contamination but also from harm to crops, the environment, and our health.
Acid rain refers to rain with a high level toxic caused by pollutants present in the air. Also known as acidic downfall, it can occur in various forms such as rain, sleet, or snow. Remember the recent discoloration (yellowish fading) of the Taj Mahal in Agra—one of India’s most iconic monuments? The reason behind this problem was acid rain.
So, what exactly is acid rain, and how does it form? Rain is considered acidic when its pH value drops below 5.6. Moreover, high AQI levels are raising concentrations of SO₂ (sulfur dioxide) and NOx (nitrogen oxides) in the atmosphere. Hence, these gases are the main contributors to acid rain. In short, more air pollution means more acid rain.
Sources of SO₂ and NOx in the Air that mix with rain:
Vehicular Emissions:
Fumes from diesel and petrol vehicles release high amounts of NOx and SO₂ into the air.
Industrial Emissions:
Factories, especially thermal power plants and steel industries, are major sources of NOx and SO₂ emissions.
Biomass Burning:
The burning of agricultural waste and even indoor cooking can release both NOx and SO₂ into the atmosphere.
What Does the Study Say About Acid Rain in India?
To understand how air pollution is causing acid rain in India, we need to look at the changing pH levels and the role of air pollution. So far, we’ve learned about the major sources of acid rain, all of which are present in the air. Now, let’s look at the evidence supporting the increase in acid rain:
Annual Rainfall Weighted Mean pH (Table 1)
| Station | 1975 | 1976 | 1977 | 1978 | 1979 | 1980 | Mean pH (All Years) |
| Allahabad | – | – | – | 6.99 | 7.46 | – | 7.16 |
| Jodhpur | – | – | – | – | – | – | 7.55 |
| Kodaikanal | – | 6.42 | – | – | – | – | 6.37 |
| Minicoy | – | – | – | 6.91 | 6.61 | 6.59 | 6.74 |
| Mohanbari | – | – | – | – | – | – | 6.02 |
| Nagpur | – | – | – | – | – | – | 6.32 |
| Port Blair | – | – | 6.44 | – | – | – | 6.50 |
| Pune | – | – | 7.21 | – | 6.78 | – | 7.02 |
| Srinagar | – | 7.54 | 7.85 | 6.88 | 7.30 | 6.87 | 7.11 |
| Visakhapatnam | – | – | 7.24 | 7.43 | 6.90 | 6.17 | 6.61 |
- General Trend:
Most stations show mean pH values above 7.0 (indicating a basic environment), except for a few locations: Kodaikanal (6.37), Mohanbari (6.02), Nagpur (6.32), Port Blair (6.50), and Visakhapatnam (6.61). These stations have pH levels closer to neutral. - Lowest Mean pH:
Mohanbari records the lowest mean pH at 6.02, still above the threshold for acid rain (pH 5.6).
Monsoon Period Rainfall Weighted Mean pH (Table 2)
| Station | 1974 | 1975 | 1976 | 1977 | 1978 | 1979 | 1980 | Mean pH (All Years) |
| Allahabad | – | – | – | 8.22 | 6.93 | 7.41 | 7.15 | 7.28 |
| Jodhpur | – | – | 7.96 | 8.28 | – | 7.16 | – | 7.34 |
| Kodaikanal | – | – | 6.18 | – | – | – | 6.06 | 6.13 |
| Minicoy | – | – | – | – | 6.87 | 6.67 | 6.67 | 6.74 |
| Nagpur | – | – | – | 6.21 | – | – | 6.36 | 6.36 |
| Port Blair | – | – | – | 6.61 | – | – | 6.49 | 6.49 |
| Pune | – | 7.44 | 7.46 | 7.08 | – | 7.79 | 6.79 | 7.06 |
| Srinagar | – | – | 7.68 | – | 7.74 | – | 6.95 | 7.35 |
| Visakhapatnam | – | – | – | 7.11 | 7.53 | 6.76 | 6.22 | 6.62 |
Specific Low pH Instances:
Kodaikanal:
In 1976, the pH dropped as low as 5.8 (based on monthly data), though the overall mean remains at 6.37.
Pune:
Monthly pH levels dipped to 6.0 in some months. The Annual Rainwater Mean (ARWM) decreased from 7.21 in 1977 to 6.78 in 1979, while the monsoon pH dropped from 7.44 in 1975 to 6.79 in 1980.
Visakhapatnam:
In 1976, all pH values recorded below 7.0. The ARWM decreased from 7.43 in 1978 to 6.17 in 1980. Moreover, the monsoon’s pH dropped from 7.11 in 1977 to 6.22 in 1980.
pH Levels of Rainwater:
Bombay recorded a pH as low as 4.5, which is way below the neutral threshold of 5.6. Furthermore, other cities, including Nagpur, Mohanbari, Allahabad, Visakhapatnam, and Kodaikanal, showed pH levels ranging from 4.77 to 5.32, indicating acidic rain. Besides, low pH occurrences have also been observed in isolated areas downwind of industrial zones, such as Chembur and Delhi.
Long-Term Trends:
A 34-year study showed a consistent increase in rainwater acidity, particularly in industrial and urban areas.
What are the impacts of Acid Rain in India?
Air pollution causing acid rain in India can feel like a double attack. Since with air pollution, acid rain have different consequences on environment, health and economy. Here are the major impacts:
Damage to the Environment:
Affecting Soil:
Acid rain can lead to soil degradation since it washes away essential nutrients like calcium and magnesium from the soil. Thus, without these nutrients, the soil becomes less fertile. As a result, farming suffers, leading to weaker crops and reduced agricultural productivity.
Water Pollution:
Rainwater is a major source of rivers and lakes in India. Therefore, when this rain becomes acidic, it can significantly increase the acidity of these crucial water bodies. As a result, it can lead to the death of fish and other aquatic animals. Further, this disrupts the natural balance of ecosystems, ultimately causing widespread damage to nature.
Damage to Buildings:
In addition to harming the environment, acid rain also affects man-made structures. Furthermore, it can slowly eat away at buildings and monuments, including iconic landmarks like the Taj Mahal. Consequently, this leads to gradual wear and deterioration, reducing the lifespan and appearance of these important cultural and historical sites.
Health issues:
Already high air quality levels (AQI) in the air can make people sick. Besides, the highly acidic level of water can result in severe health conditions, too.
Some rural places of India still depend on rainwater harvesting, natural sources as lakes and rivers. The population of these areas tend to expose to more water pollution.
Economical Issue:
The damage to nature and people’s health costs a lot of money. Because this includes high hospital bills and lost crops from farms.
Thus, to control the air pollution causing acid rain in India, we have to control the air pollution first. As quoted by the scientist of IMD, “At present levels, these effects are not widespread. But this is a trend we need to monitor closely. “ Reported Economic Times. It highlights that the issue can be concerning in the coming years. While many mitigation efforts offer a hope to control the pollution levels still need advanced solutions to combat.
