Table 1. Symptom prevalence and other characteristics of the study cohort by zone and year (n = 2978).

	Reduced exposure zone			Increased exposure zonea			Eastern stack zonea			Control zone
	2006	2007	2008	2006	2007	2008	2006	2007	2008	2006	2007	2008
n	1024	756	608	589	422	302	645	500	394	768	537	424
(% of 2006)		(74)	(59)		(72)	(51)		(78)	(61)		(70)	(55)
%
Adult (age ≥18 yrs)	72	70	68	74	72	71	75	72	72	72	72	72
Female	56	57	58	53	54	57	54	53	54	53	54	54
Diagnosed asthma	18	20	20	18	24	21	16	19	21	15	17	19
Current asthma	11	13	13	12	14	12	9	12	12	9	10	9
Wheeze	15	18	15	14	19	18	11	20	17	10	13	13
Asthma medication	11	14	15	11	14	14	10	14	13	9	10	11
Inhaled corticosteroids	6	8	9	4	8	7	4	7	6	5	5	7
Cough	40	49	50	33	52	48	36	52	53	34	47	48
Lower resp. symptomsb	39	47	47	35	51	50	34	48	52	33	43	43
Severe lower resp. symptomsb	10	11	12	12	14	13	8	17	12	8	9	10
Upper resp. symptomsb	17	24	22	10	25	28	12	27	25	12	22	20
Mouth symptoms	14	17	18	9	21	21	11	24	22	13	17	18
Smoker c	7	6	6	12	10	9	11	9	7	12	13	10
Home environmental factors
Unflued gas heater	25	28	33	12	21	25	18	25	27	20	24	29
Gas cooktop or oven	52	58	59	25	52	51	44	56	56	42	46	48
ETSd at home	7	3	4	14	9	10	8	5	5	8	5	7
Educational status
Tertiary educated	61	65	64	46	46	44	62	61	61	44	42	36
High school/diplomae	31	28	28	43	38	41	31	34	31	43	38	46
Up to middle schoolf	8	8	8	11	16	15	7	6	7	13	19	18
Work status
Paid Work	74	76	77	66	70	70	75	76	78	71	70	73

^aParticipants in overlapping area of increased exposure zone and stack zone, entire cohort (2006 = 48; 2007 = 24; 2008 = 15) contributed data to both zones.

^bComposite variables derived from questionnaire data (see Supporting information, Table S1).

^cSubjects <18 years assumed to be non-smokers.

^dEnvironmental tobacco smoke.

^eIncluded Diploma/TAFE, and participants who responded “Other”.

^fIncluded participants who refused to respond.