Are current pharmaceuticals levels in natural waterways dangerous?

Dangerous to what?

To humans touching the water or swimming in it? No.

Drinking a few mouthfuls (not that you would do this voluntarily)? No.

As an acute toxicity threat to biota (insects, fish)? No.

As a mechanism for inducing sub-lethal effects in stream organisms and essential ecosystem services like photosynthesis and nutrient cycling. Almost certainly.

Sub-lethal effects can range from insects emerging earlier from the water at lower weights, which then affects their predators food supply, behavioural responses e.g. changed predator-prey relationships in fish in response to antidepressants in the water for example, inhibition of photosynthesis in stream plants (including biofilms) which then lowers the food supply available to higher order organisms in the food web.

Hence these pharmaceuticals at concentrations found in most waterways around the world are termed 'Ecosystem Disruptors'.