Table 4 Mean and standard deviation of residential and time-activity adjusted annual average particle number concentrations (presented as 10,000 particles per cm³) from sequential model adjustment by distance to I-93 and stratified by employment status for clinic attending participants.

PNC models	Total	≤50 m	51–500	>1,000 m
All clinic participants	(n=140)	(n=20)	(n=95)	(n=25)
RAA	2.5 (0.4)	2.7 (0.1)^a	2.6 (0.1)^b	1.8 (0.1)
RAA+AC	2.4 (0.3)	2.7 (0.1)^a	2.6 (0.1)^b	1.8 (0.1)
RAA+work	2.4(0.3)	2.4 (0.2)^a	2.5 (0.2)^b	1.8 (0.1)
RAA+work+other	2.3 (0.3)	2.4 (0.2)^a	2.4 (0.1)^b	1.8 (0.1)
RAA+work+other+highway	2.3 (0.3)	2.4 (0.2)^a	2.4 (0.1)^b	1.8 (0.1)
RAA+work+other+highway+AC	2.3 (0.3)	2.4 (0.2)^a	2.4 (0.2)^b	1.7 (0.1)
Working full or part time	(n=62)	(n=14)	(n=32)	(n=16)
RAA	2.4 (0.4)	2.7 (0.1)^a	2.6 (0.1)^b	1.8 (0.1)
RAA+AC	2.4 (0.4)	2.7 (0.1)^a	2.6 (0.1)^b	1.8 (0.1)
RAA+work	2.2 (0.3)	2.4 (0.2)^a	2.4 (0.1)^b	1.8 (<0.1)
RAA+work+other	2.2 (0.3)	2.4 (0.2)^a	2.3 (0.1)^b	1.8 (<0.1)
RAA+work+other+highway	2.2 (0.3)	2.4 (0.2)^a	2.4 (0.1)^b	1.8 (0.1)
RAA+work+other+highway+AC	2.2 (0.3)	2.3 (0.3)^a	2.3 (0.2)^b	1.8 (0.1)
Non-working, retired or disabled	(n=78)	(n=6)	(n=63)	(n=9)
RAA	2.5 (0.3)	2.7 (0.1)^a	2.6 (0.1)^b	1.8 (0.1)
RAA+AC	2.4 (0.3)	2.7 (0.1)^a	2.5 (0.1)^b	1.7 (0.1)
RAA+work	2.5 (0.3)	2.7 (0.1)^a	2.6 (0.1)^b	1.8 (0.1)
RAA+work+other	2.4 (0.3)	2.6 (0.1)^a	2.5 (0.1)^b	1.8 (0.1)
RAA+work+other+highway	2.4 (0.3)	2.6 (0.1)^a	2.5 (0.1)^b	1.8 (0.1)
RAA+work+other+highway+AC	2.3 (0.3)	2.6 (0.1)^a	2.4 (0.2)^b	1.7 (0.1)

Residential annual average (RAA): PNC values for all hours of the year to the participant’s place of residence. Work: an average higher or lower PNC was inserted for every hour a participant indicated being in the work micro-environment and based upon TRAP exposure job categorization. Other: an urban background average was inserted for every hour a participant identified as being in the “other” micro-environment. Highway: modeled side of highway values was inserted for indicated time spent on highway. Air conditioning (AC): a % reduction when ambient hourly temperatures were above 21 °C (70 °F) was applied to PNC values for the micro-environment inside home when participants identified as having and using window or central AC.
^aIndicates significant mean difference between the ≤50 m and >1,000 m distance group.
^bIndicates significant mean difference between the 51–500 m and >1,000 m distance group. Sequential PNC adjustments are based upon each participant’s individual time-activity questionnaires.

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