Table 1.

Sequence of exposure patterns followed in this study for all 4 cohorts

	1st Exposure	Washout	2nd Exposure	Washout	3rd Exposure
Sequence	(5 days)	Period (days)	(5 days)	Period (days)	(5 days)
1	A	9	B	9	C
2	B	9	C	9	A
3	C	9	A	9	B
4	A	9	C	9	B
5	B	9	A	9	C
6	C	9	B	9	A

Note: Cohorts 1–4 were spaced by time and the entire exposure took place from May–August 2010

A Bayview Mask, B Bayview Ambient (without mask) and C College