From your link in [1]<p>&gt; The meta-analyses showed a statistically significant association between risk for lung cancer and PM10 (hazard ratio [HR] 1·22 [95% CI 1·03–1·45] per 10 μg&#x2F;m3). For PM2·5 the HR was 1·18 (0·96–1·46) per 5 μg&#x2F;m3.<p>The increase of risk of lung cancer was NOT significant with PM2.5 ratio. Only with PM10.