Is riding on Mine dumps dangerous for our health????

Here's one that I hope some of our learned fellow Wilddog's can answer, I asked myself this question a couple of months ago when riding the dumps at Maraisburg, and watching Carte blanche last Sunday about the Uranium in the water in the West Rand areas, is riding on these dumps dangerous to our health? when you consider the cyanide and now Uranium  implications particularly on the older dumps where the exctraction methods were not as good years ago as they are today, hope there are some Medical buffs here. ???