Oh yes, there's a very real risk of that mate. There's also a high risk of catching leptospirosis from rat piss, ornithosis from pigeon shit, getting bitten by any number of angry critters (a colleague had half his finger bitten off by a squirrel when he lifted up a loft hatch to investigate reported noises), becoming sensitised to wasp stings and going into anaphylactic shock or even poisoning ourselves with all the biocides we carry. We just have to be careful that's all. I'm just thankful I'm not doing the same job in Australia - now that would be fun...