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The cigarette equivalent is a method for visually comparing the harm from air pollution with the harm from smoking. Researchers at Berkeley Earth developed a methodology that allows converting the concentration of fine particulate matter PM2.5 in the air into the number of cigarettes smoked per day with equivalent health harm.
This analogy helps people better understand the scale of the air pollution problem, as the risks from smoking are widely known and understood. When we say that breathing air with a certain PM2.5 concentration is like smoking a certain number of cigarettes per day, it makes the threat more tangible and understandable.
A cigarette equivalent is a way to express the long-term health effects of air pollution through an analogy with cigarette smoking. Research shows that both passive smoking and breathing polluted air cause similar diseases: lung cancer, cardiovascular diseases, chronic obstructive pulmonary disease (COPD), and others.
It's important to understand that this doesn't mean air pollution and smoking are identical in their effects. It's merely a way to quantitatively assess health risks using a familiar unit of measurement — a cigarette.
Based on analysis of numerous epidemiological studies, Berkeley Earth derived the following formula:
1 cigarette per day ≈ 22 μg/m³ PM2.5
This means that if a person breathes air with a PM2.5 concentration of 22 μg/m³ throughout the year, it has the same long-term health impact (in terms of premature death risk) as if they smoked one cigarette per day during the same period.
Calculation formula:
Cigarettes per day = Annual average PM2.5 concentration (μg/m³) / 22
This methodology is based on data about the long-term effects of air pollution and smoking on mortality from cardiovascular diseases and lung cancer. The key study Berkeley Earth relies on is the work of Pope et al. (2016), published in Environmental Health Perspectives.
To better understand how this methodology works, let's look at examples for various PM2.5 pollution levels:
| Annual Average PM2.5 Concentration | Cigarette Equivalent (cigarettes per day) | Pollution Level Description |
|---|---|---|
| 5 μg/m³ | ~0.23 cigarettes | WHO target level (2021). Clean air. |
| 10 μg/m³ | ~0.45 cigarettes | WHO interim target (IT-4). Acceptable air quality. |
| 22 μg/m³ | 1 cigarette | Base unit of cigarette equivalent. |
| 35 μg/m³ | ~1.6 cigarettes | WHO interim target (IT-1). Moderate pollution. |
| 50 μg/m³ | ~2.3 cigarettes | Level often observed in Yerevan during winter. |
| 100 μg/m³ | ~4.5 cigarettes | Heavy pollution. Peak days in Yerevan. |
| 150 μg/m³ | ~6.8 cigarettes | Very heavy pollution. Hazardous to health. |
| 200 μg/m³ | ~9.1 cigarettes | Extreme pollution. Critical level. |
The cigarette equivalent helps understand the long-term health risks from air pollution:
