Potential sources of bias in the use of individual's recall of the frequency of exposure to air pollution for use in exposure assessment in epidemiological studies: a cross-sectional survey

Table 1 Single-variable analyses of increased reporting of industrial odour pollution.

Variable		Reduced reporting of industrial pollution		Median reporting of industrial pollution		Increased reporting of industrial pollution		P value^a
		n	%	n	%	n	%
Presence of child in the home	No	688	28	1050	42	754	30	<0.0001
	Yes	210	23	343	38	357	39
Presence of person in home with respiratory symptoms	No	677	29	1003	44	622	27	<0.0001
	Yes	221	20	390	35	489	44
Believes industrial pollution is harming their health	No	184	29	367	58	84	13	<0.0001
	Don't know	485	33	636	44	337	23
	Yes	219	17	390	30	690	53
Occupational class	1	36	12	172	59	82	28	<0.0001
	2	108	17	314	48	226	35
	3NM	121	27	159	36	162	37
	3M	178	25	268	37	272	38
	4	167	35	150	32	154	33
	5	33	31	37	35	35	33
	Undetermined	255	35	293	40	180	25
Ownership of home	Own home	593	23	1104	43	853	33	<0.0001
	Rented	310	37	283	33	252	30
Uses gas for heating or cooking	No	304	24	613	48	367	29	0.4267
	Yes	592	28	777	37	741	35
Has double glazing	No windows	377	31	449	37	391	32	0.008
	Some windows	122	21	290	49	178	30
	All windows	395	25	653	41	539	34
Own pets	No	542	29	751	40	583	31	0.0006
	Yes	351	23	637	42	522	35
Current smoker in house	No	575	25	992	43	760	33	0.0585
	Yes	323	30	401	37	351	33
Ever smoker in house	No	331	24	608	44	437	32	0.3654
	Yes	567	28	785	39	674	33
Reports noise from neighbours	No	757	28	1184	43	783	29	<0.0001
	Yes	141	21	209	31	328	48
Reports other people's smoke	No	833	29	1219	42	826	29	<0.0001
	Yes	65	12	174	33	285	54

ISSN: 1476-069X