Roles of the human occupant in indoor chemistry

"Human occupants, through the reactive chemicals that they emit, have a large influence on
the atmospheric chemistry that occurs around them, ultimately impacting their own chemical
exposures and their health" --A recent article published in the journal Indoor Air by Charles J. Weschler from the Environmental and Occupational Health Sciences Institute, Rutgers University gives an overview on roles of the human occupant in indoor chemistry.

As summarized by Weschler, a number of evidences suggested that there are pronounced influences of humans on chemistry within the indoor spaces they inhabit.

Occupants leave behind skin flakes, skin oils and body effluents on indoor surfaces and on their clothing. These human generated long-chain hydrocarbon involve unsaturated carbon bonds, which will react with indoor ozone and thus affect indoor chemical reactions involving ozone.

This review article also summarized the potential role of occupants on the levels of semivolatile organic compounds from indoor sources, which is based on a human uptake and exposure model coupled with an indoor chemical fate mass balance model that suggests human intake and elimination of a chemical (e.g., biotransformation, renal excretion, fecal egestion, hand washing, bathing)
influences its fate indoors. Such an impact varies according to chemicals properties (volatility, degradation, etc) as well as environmental characteristic (e.g., ventilation) and human behaviors (e.g. the frequency of cleaning. As mentioned by Wescler, this is an area that is potentially rich
for further exploration. Refer to this modeling study for more information.

Some facts summarized in the article:

• lipids on skin surface of human are a combination of sebum secreted by sebaceous glands and lesser amounts of lipids from the stratum corneum
• The chemicals that constitute skin surface lipids include triacyl glycerols (~25%), unesterfied fatty acids (~25%), wax esters (~22%), squalene (~10%), mono- and diacyl glycerols (~10%) and lesser amounts of sterol esters, sterols, phospholipids and other species 
• squalene is responsible for roughly 50% of the unsaturated carbon bonds in skin surface lipids

Finally, the review article by Weschler provides a summary on the roles of the human occupant in indoor chemistry- "We have read the early pages of what promises to be a long and interesting book –interesting, in part, because the subject is us. This unfolding story promises to inform strategies designed to protect our health, our technical devices and our cultural artifacts"

References and more to read: 

http://dx.doi.org/10.1111/ina.12185

http://dx.doi.org/10.1021/es502718k