Posted By Jane Blunt This is a difficult one. Titanium dioxide has a relatively high exposure standard - 10 mg/m3 total inhalable dust, and 4 mg/m3 respirable dust (UK). It is chemically stable. However, I would expect the hydrocarbon resins and the mineral oil to react with the air and produce a variety of decomposition products, including water, carbon dioxide and carbon monoxide, along with a whole host of miscellaneous things. Most of these would be in reasonably small quantities. You cannot rule out the possibility that some were quite toxic, depending on the chemical nature of the resins and oils. You say the person was overcome, but you also say that he was sent home, which suggests that it was extreme nuisance, rather than a medical collapse. The chemicals mentioned by name above would only have a short term effect, after all water and carbon dioxide are normal constituents of the atmosphere. Carbon monoxide is very toxic, but the body can deal with small quantities without long term effects. The unidentified chemicals are less easy to say for sure, but bear in mind that the exposure was only once, and that most of us expose ourselves from time to time to decomposition products such as these when we throw things on bonfires! If the person is seriously concerned, or has symptoms that persist, he should seek a medical opinion. Jane