I think it is too high really to cause any health issues (at the moment).
We may get some spectacular sunsets though!
If it continues to spew out loads of ash for an extended period of time I think there is the potential for it to affect the average temperature by a small amount, and affect our weather, but I think thats too early to call.
I need to do some digging, I seem to remember some concerns about this at the time of the original eruption in March, although I am not sure if that was related to a concern this eruption could trigger a second one in another volcan, one with more potential for disruption.
It's very interesting.