If anonymity is a concern, please don't worry about it. We would certainly like to have some basic contact information for you (i.e., an e-mail address and, hopefully, a phone number) but if you don't even want that information to go to the government, we will look after that.
We recommend you keep a diary for this specific purpose. Please provide as much detail as you're comfortable with. For example, if you'd rather not provide your full address, please consider providing the street name or, at the very least, the town/city. And dates and times (or frequency of exposure) are good too... and temperatures as well. And any other details you may consider pertinent.