Total OH reactivity of Human Beings

Humans are a potent yet understudied source of volatile organic compounds (VOCs). They can influence indoor air quality and chemistry by directly emitting volatile organic compounds through their breath, skin, clothing, personal care products and activities. Furthermore, emitted VOCs can react with the main atmospheric oxidants present indoors, such as ozone and the hydroxyl radical (OH).

The ICHEAR (Indoor Chemical Human Emissions and Reactivity) project (Bekö et al., submitted) aimed at examining the impact of human bioeffluents, such as dermal and breath emissions, indoors. Several conditions were tested inside a stainless steel climate chamber occupied by four volunteers. In most of the experiments, ozone was introduced into the chamber to initiate indoor oxidation reactions, whereby the largest sink of ozone is ozonolysis of skin lipids.

We measured the total OH reactivity i.e. the total loss frequency of OH radicals from human bioeffluents and combined it with direct VOC measurements, in order to verify that (i) the budget of human emissions is closed; and to (ii) determine the OH concentration generated by human ozonolysis. Specifically, here we examine the role of ozone on the OH reactivity of four adult occupants (whole body and dermal only), wearing short/long clothing, at moderate temperature and low humidity.

The human oxidation capacity, through OH production by alkenes-ozone reactions is calculated and discussed.