Altmetric
We use Altmetric to track reader engagement with articles. Altmetric is a web-based service that monitors how much attention an article receives through various news media, social media, academic networking sites, blogs, and more.

These statistics give readers a general idea about the amount of interest an article has generated. However, Altmetric cannot track every news and social media outlet on the web. So some mentions may not be included in an article’s Altmetric score.

Dimensions
We also use Dimensions, a citation database that shows how often an article has been cited in the scientific literature, patents, grants, and clinical trials. Dimensions data reflect the scholarly, policy, and translational outcomes of research articles.

PDF Downloads
The download metrics listed on the individual article pages reflect the number of times the PDF of the article has been downloaded from the EHP website since 1 September 2018. We are unable to provide PDF download data prior to that date for any article.