Inhalable Microplastics & Urban Air Pollution

Inhalable Microplastics (IMPs)?

• Definition: Plastic particles < 10 micrometres (µm) that can be inhaled.

• Critical feature: Small enough to bypass nasal filters and penetrate deep lung alveoli.

• Categorised as emerging airborne contaminants (beyond PM2.5/PM10).

Why are they a serious concern?

(a) Trojan Horse Effect

IMPs adsorb and transport toxic co-pollutants, including:

• Heavy metals: Lead (Pb), Cadmium (Cd)

• Endocrine Disruptors: Diethyl phthalates

• Microbes: Harmful fungi (Aspergillus fumigatus)

• Antibiotic-resistance genes (ARGs)

➡ Converts physical pollution into chemical + biological hazard.

Key Study 

• First comprehensive Indian study on inhalable microplastics

• Lead institution: IISER Kolkata

• Lead author: Prof. Gopala Krishna Darbha

Study Design

• Sampling at human breathing height (1.5 m)

• Locations: High-footfall markets in
  Delhi, Mumbai, Kolkata, Chennai

Major Fidings 

(a) Average Exposure

• Mean concentration: 8.8 µg/m³

• Daily inhalation: ~132 micrograms per person per day

“This is a very high daily dose of pollution.” – Prof. Darbha

City-wise Exposure

• Atmospheric lead levels:
  Kolkata > Delhi > others

Seasonal Variation

• Winter evenings: 32.7 particles/m³

• Non-winter evenings: 18.8 particles/m³

• 74% increase in winter

Causes:

• Temperature inversion

• Low wind speed

• Poor dispersion conditions

Sources of Inhalable Microplastics

Primary Sources

• Synthetic textiles (polyester clothing)

• Toy fillings

• Tyre wear (highly carcinogenic)

Secondary Sources

• Packaging waste

• Cosmetics

• Construction dust

• Household activities

• Waste burning

• Mini & micro-industries

High-risk locations:

• Chandni Chowk (Delhi)

• Sealdah Market (Kolkata)

Types & Size Distribution

• 11 plastic types identified

• Particle sizes:

  • < 100 µm → 56.2%

  • 100–500 µm → 24.7%

  • 500 µm → 19.1%

• Fragments > Filaments

  • Fragments → Packaging, tyre wear, waste

  • Filaments → Textiles, toy stuffing

Health Impacts

Chronic exposure associated with:

• Lung cancer

• Hormonal disorders

• Breast-related diseases

• Respiratory illnesses

• Antibiotic-resistant infections

Most vulnerable groups:

• Traffic police

• Construction labourers

• Street vendors

Why AQI Fails to Capture This Threat

• AQI focuses on:

  • PM2.5, PM10, SO₂, NO₂, O₃, CO, Pb

• Microplastics & nanoplastics not explicitly monitored

• Correlation with AQI is still preliminary

Persistence in Air

• IMPs have low gravitational settling velocity

• Remain suspended for long durations

• Can travel long distances

Policy Gaps & Recommendations

Identified Gaps

• Poor waste segregation

• Uncontrolled plastic disposal

• Open waste burning

• Weak regulation of synthetic textiles

Suggested Measures

• Ban single-use plastics

• Promote cotton-based clothing

• Regulate recycled polyester

• Strengthen waste management systems

• Occupational protection for high-risk workers

• Include microplastics in air quality monitoring frameworks

Conclusion

Inhalable microplastics represent the next frontier of air pollution—where solid waste, chemical toxicity, and microbial resistance converge, demanding urgent regulatory and scientific attention.

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