Figure 2. Level of exposure to fine particulate matter and the risk of deep vein thrombosis (DVT). The graph demonstrates the observed relationship between the relative risk of DVT and the level of particulate matter of less than 10 µm in aerodynamic diameter (PM₁₀) in the year preceding the diagnosis. These results suggest a linear relationship between exposure and risk, though the 95% confidence intervals (shaded areas) are wide at the extremes of exposure. Risk is depicted in comparison with a reference value of 12.0 µg/m³ (minimum observed PM₁₀ level). The histogram in the bottom part illustrates the density of exposure distribution for air pollution. Risk estimates are adjusted for age, sex, year of diagnosis, area of residence, body mass index, education, current use of oral contraceptives or hormone therapy, Leiden V or prothrombin mutations, season, and ambient temperature.