Despite scientific evidence showing that PM1: particulate matter smaller than 1 micron is far deadlier than PM2.5, India has no regulatory standards or monitoring for it. 

• New studies indicate PM1 levels in Delhi may be underestimated by 20% (or ~50 μg/m³), amplifying health risks.

What is Particulate Matter 1.0 (PM1)?

• Definition: PM1 refers to particulate matter with a diameter smaller than 1 micron.
• Ultrafine Nature: PM1 is ultrafine and can bypass the body’s natural defence mechanisms in ways that larger particles cannot.
• Sources: ​​Emissions from modern vehicular engines, industrial emissions, biomass burning, construction dust and recondensed metal vapours.
  • Because of their minute size, these particles are not easily dispersed and remain suspended in the air we breathe.
• Comparison with Other Particles:
  • PM10: Mostly blocked by nasal hair and mucus.
    • They are linked to bronchitis, asthma, and upper respiratory infections. They often aggravate existing conditions rather than cause new ones.
  • PM2.5: Reaches deep into the lungs.
    • Penetrate deep into the lower respiratory tract, causing cardiovascular issues.
  • PM1: Small enough to penetrate the alveoli, enter the bloodstream, and in some cases, even pass through the skin.
  • PM10, PM2.5, and PM1 levels collectively represent particulate pollution, with PM1 constituting a significant fraction of PM2.5.
• Chemical Load: Carries lead, cadmium, nickel, chromium and other carcinogenic heavy metals.
• Deep Physiological Access: Causes systemic inflammation, oxidative stress, cellular damage, and poses heightened risks of heart disease, stroke, asthma and cancer.
• Proportion of PM 2.5: PM1 constitutes nearly 50% of the PM2.5 concentration, making it a major component of fine particulate pollution.
• Surface Chemistry: Its high surface-area-to-volume ratio means greater toxic chemical adsorption than PM2.5.

Absence of Regulatory Framework

• Lack of Standards: Neither the World Health Organization (WHO) nor India’s Central Pollution Control Board (CPCB) has established standards or permissible limits for PM1.
  • PM1 is absent from CPCB’s National Ambient Air Quality Standards; such threshold values or legal norms do not exist.
• Technology Constraints: Lack of approved real-time PM1 samplers, limited scientific expertise, and absence of validated measurement protocols delay regulation.
• Global Scientific Warnings: Researchers worldwide caution that PM1 may cause significantly more harm than PM2.5 and PM10 due to its ultrafine size and toxicity.

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Recommendations

• Set PM1 Standards: Establish National Ambient Air Quality Standards (NAAQS) for PM1 based on global research.
• Upgrade Monitoring Network: Integrate PM1 sensors into CAAQMS; validate real-time regulatory-grade PM1 samplers.
• Strengthen Source Control: Target vehicular ultrafine emissions, industrial combustion and metal vapours.
• Adopt Urban Planning Measures: Reduce hotspots through low-emission zones, green buffers, dust control and better traffic management.
• Promote Indoor Air Standards: Encourage PM1 filtration in public buildings, schools and hospitals

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