Smog Calculator (Benzo[a]pyrene)

Smog is a mixture of air pollutants — smoke, fog, and chemical fumes — that forms under certain atmospheric conditions. Benzo[a]pyrene (B[a]P) is one of the most toxic components of smog, classified as a Group 1 carcinogen by the IARC. It forms during incomplete combustion of organic material such as coal, wood, and vehicle fuel, and is strongly linked to lung cancer.

The calculator uses the known fact that smoking one cigarette delivers approximately 1–4 ng of benzo[a]pyrene to your lungs. We use 1 ng per cigarette as a conservative reference. Your annual B[a]P inhaled (based on breathing rate ~0.83 m³/hour, time outdoors, time indoors at 90% outdoor concentration, and days of exposure) is divided by this per-cigarette value to yield a meaningful, relatable number.

The European Union sets a target value of 1 ng/m³ for the annual average concentration of benzo[a]pyrene in ambient air. Many cities in Central and Eastern Europe, particularly during winter heating seasons, can exceed this value several times over — meaning residents effectively 'smoke' dozens of cigarettes worth of B[a]P per year just by breathing.

PM₂.₅ and PM₁₀ refer to particulate matter with diameters smaller than 2.5 and 10 micrometers respectively. These fine particles carry adsorbed chemicals — including benzo[a]pyrene — deep into the lungs. B[a]P binds primarily to PM₂.₅, making fine particle pollution especially hazardous in smoggy conditions.

Outdoor air infiltrates buildings through windows, doors, and ventilation systems. Research shows that indoor B[a]P concentrations typically reach around 90% of outdoor levels. This means you continue to inhale significant amounts of pollutants even when staying inside, so both indoor and outdoor time must be included for an accurate estimate.

The primary sources include residential heating using coal, wood, and biomass burning (especially in winter), vehicle exhaust (particularly diesel engines), industrial combustion processes, and waste incineration. In many European cities, domestic solid-fuel heating contributes over 80% of ambient B[a]P during cold months.

Long-term B[a]P exposure is strongly associated with lung cancer, as well as cancers of the skin, bladder, and digestive tract. It also causes cardiovascular damage, impairs immune function, and is particularly harmful to developing fetuses and children. Even short-term elevated exposure can trigger respiratory symptoms and oxidative stress.

Practical steps include checking local air quality forecasts and limiting outdoor time on high-smog days, using high-quality air purifiers with HEPA filters indoors, keeping windows closed during smog episodes, wearing N95 or FFP2 masks when outdoors in polluted conditions, and advocating for cleaner local heating and transport policies.