ERIw	is the Exposure Ranking Index for a specific subject (responder or worker) identified by index w (who may be have been involved in different activities during different exposure events)
Fcliud, w	is an exposure-related factor accounting for direct contact of the specific responder or worker with the dust cloud on September 11, 2001
fact	is an exposure-related factor accounting for each type of WTC-related activity (search and rescue, cleanup, etc.)
i = 1, … M	is a counting index for outdoor exposure events during day i where i=1 on 9/11/2001
j = 1, … N	is a counting index for indoor (i.e. confined space) exposure events during day j where j=1 on 9/11/2001
f*time	is an “adjusted” exposure-related factor accounting for the time aspects of each exposure event [f*time=function(fdate, i) where fdate, i is a factor associated with date relative to 9/11]
floc, ϕloc	are exposure-related factors accounting for the locations where subject spend the majority of the exposure event (typically, but not exclusively, work shift)
μj	is a microenvironmental adjustment factor reflecting any information, if available, specific to the confined space settings of the exposure event
p	is a personal protective equipment (PPE) factor, reflecting the type and usage of PPE during the exposure event
Δti, Δτj	is a factor reflecting the duration of exposure event during day i or j