http://www.oilseedrape.org.uk/html/uk.html

I would agree with Steve as regards the potential toxicity of certain agricultural sprays. I am not sure to what extent the latest EU regulations have been implemented in the uk.
They would require annual certification of sprays units(probably exempting back pack sprayers)
Formal qualification and registration of operators
Bunded storage of liquid chemicals
Complete records of type, dosage rate, location, date.
Registering of all commercial sales of agricultural chemicals.
Non compliance would attract a variable penalty taken from the SFP
Even with all the proposed legislation there would seem to be little account taken of spray drift and proximity to houses or schools.
Perhaps account of wind direction and strength should be more than "advisory"
http://adlib.everysite.co.uk/adlib/defra/content.aspx?id=000IL3890W.16NTBWTW6M4U3