prevalent in rivers and oceans than drinking straws, which have been the target of previous clean up drives. they said they hope that identifying the sources of plastic litter will make it easier to tackle the problem. regular and strenuous exercise increases the risk of motor neurone disease in people who are genetically vulnerable according to a study. researchers at the university of sheffield say the number of high profile athletes who have developed the disease is not a coincidence. the scientists say nobody should stop exercising as a result of the study, but they hope the findings could lead to ways of screening people who may be at higher risk. asa as a clinician doing clinics for patients with mnd, i have always suspected that being a fit athletic sort of person is a risk factor but the studies that have been done until now in the medical literature