as a doctor in southern west virginia, daniel doyle often treats coalfield residents. one of the clinics he works at is just outside charleston, so he's also been seeing people who were impacted by january's chemical spill. >> it's a huge population cohort study and it will take us 10 20, 30 years - maybe longer - to know what the long term effects are. no question that it's an experiment, but mountaintop removal is an experiment. the water pollution that is taking place is an experiment. >> do you see the health consequences of mountain top removal on the people who live around it? >> definitely in the last eight years there's been a series of epidemiological studies finding clear association between mountain top removal and cardiovascular disease, heart attacks, birth defects, certain cancers and so there's a body of knowledge which coal companies are actively investing in discrediting by sponsoring their own research institutes to try to find flaws in this. this is news that people don't want. >> watch more "faultlines" on demand or visit aljazeera.com/faultlines. >