Last year the nonprofit Ocean Conservancy reported that cigarette butts, which contain plastic and toxic chemicals, were the most-littered item at their global beach cleanups
[1] If you're at a complete loss, ask the employees for recommendations
Meliker JR, Slotnick MJ, AvRuskin GA, Schottenfeld D, Jacquez GM, Wilson ML et al (2010) Lifetime exposure to arsenic in drinking water and bladder cancer: a population-based casecontrol study in Michigan, USA
Cancer is a disease caused by DNA damage, and the team, including Ludmil Alexandrov of Los Alamos National Laboratory and Mike Stratton of Britain's Wellcome Trust Sanger Institute, found a lot of damage
My money is on this too
The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies