Thanks for all the replies and advice :-)

Unfortunatley we don't have a back yard: apartment terrace 4 floors up
overlooking a main road. It's a lovely spot, the traffic pollution is the
only worry. The noise is actually okay, but less would always be better.

I've come across a lot of info on people planting veggie gardens in the
inner city, but not much yet on the health side so I'll do a bit of
research into it. I wrote to a government environmental web site once
inquiring about the goverment's stance on improving air quality with regards
to diesel fumes, but they didn't reply. Perhaps the phone will be a more
effective means of communication.

In spring just gone, I planted a row of shrubs which will grow to a
reasonable height in about 5 yrs, so I'm hopeful that that might cut out
some of the dust and noise. I've not had to deal with it before, so I'm
looking forward to seeing what the results are. When I lived down the road
from here, on the other side of the block, the dust we got was much cleaner
to look at - more fluffy and light grey. I really was surprised at the stuff
we get round the front.

I tell myself with all the time I spend trying to create a little oasis in
the city, that there are benefits to it. It certainly makes the place more
pleasant and I'm sure that our overlooking neighbours also benefit. At least
it'll increase the value of the property if we ever sell the place!

I'll still consider getting a worm farm and using it on the veggies. I also
thought it odd advice from the company rep. If I consider the same product,
I'll talk to someone else there and ask more questions. I'll also post any
info I get on the diesel dust.


;-)