India is known to have poor air quality. The Air Quality Life Index ranks India as the second-most polluted country in the world, largely due to rapid urbanization and industrialization.

Fine particles of particulate matter cause respiratory illnesses, especially impacting the old and the young. The finer the particles, the greater the risk.

Northeast India has the highest infant mortality rate in the country, and the overall mortality rate is 25% higher than the national average. Toxic metals mined in the area (including chromium, iron, and lead) produce free radicals that affect both DNA and the pulmonary system.

Developed countries are often more successful at monitoring regions for various PM components, but in India only the total masses of PM10 and PM2.5 are currently routinely measured. Understanding PMs temporal variations, composition, and sources is critical to develop an effective regional control strategy.

In this study, researcher Rajyalakshmi Garaga observed seasonal variations in PM and its chemical components. Her objective was to identify the most dangerous source of PM using source apportionment and health risk analysis.

In “Health Risk Assessment of Different Sources of Metals in PM10 and PM2.5 in the Largest City in Northeast India,” Garaga collected samples twice a day for 13 months in a residential neighborhood in Guwahati and presents monthly variations in the metals. She further analyzes the high pollution events by comparing the different sources of PM on clean and polluted days in each season to determine if they were a result of the weather or an increase in emissions.

Learn more about his results and what can be done to improve air quality in Northeast India in the Journal of Hazardous, Toxic, and Radioactive Waste, at The abstract is below.


Northeast India, home to a population of 46 million, has the highest infant mortality rate in the country. Some of these infant mortalities might be attributed to exposure to toxic air pollutants, especially heavy metals. To explore this, seasonal changes in the source contributions of these metals were studied, using a positive matrix factorization model, in a residential area in the largest city in the region. The mean particulate matter with aerodynamic diameter ≤ 10 and ≤ 2.5 µm (PM10 and PM2.5) concentrations were found to be 90 and 69 μg/m3, respectively. Particles from biomass burning, coal mining, Dust emissions types 1 and 2, and industry and vehicular emissions were found in both PM10 and PM2.5. A comparison between the source contributions to PM10 and PM2.5 during clean and pollution days revealed that the highest concentrations were not only due to stagnant weather conditions, but also to changes in emissions from the different sources. Further analysis was carried to estimate the overall health risk associated with each source and the carcinogenic risk from the metals. The results revealed that more emphasis should be given to the health effects associated with each source when designing control strategies, rather than just concentrating on the source that contributes the maximum mass.

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