The most relevant effect of particulate matter in air, on human health is:

CONCEPT

Particulate matter (PM) is the mixture of fine solid and liquid particles suspended in air (e.g., PM10, PM2.5). Once inhaled, these particles penetrate and deposit deep in the respiratory tract, and irritant/inflammatory damage to lung tissue is the most direct, consistently documented health impact of PM exposure recognised by bodies such as the WHO and the US EPA.

APPLICATION

Among the listed effects, aggravation of respiratory disease is the outcome most strongly and repeatedly linked to particulate-matter exposure in large-scale epidemiological evidence and health-agency guidance, because inhaled particulates irritate and inflame airway and lung tissue, worsening existing conditions such as asthma, bronchitis and COPD.

CONTRAST

• Impaired blood formation is characteristic of pollutants such as lead, which interferes with heme synthesis during haematopoiesis, not of suspended particulate matter itself.

• Chest tightness is a transient, non-specific sensation that can accompany many air-quality episodes; it is not the standard classification used by major health bodies for particulate matter's health impact.

• Headache and rise in blood pressure level have some documented association with long-term PM exposure, but they are non-specific, systemic responses (also linked to noise pollution, stress and other pollutants) rather than the principal, best-characterised effect of particulate matter.

Result: aggravation of respiratory disease is the correct and best-supported answer (WHO and the US EPA both cite respiratory irritation/aggravation as the principal documented health effect of particulate matter).