Table 5.

Comparison of carbonyl concentrations (in ppb) in industrial and non-industrial areas.

Compounds	Industrial area (Mean ± S.D., n = 327)	Non-industrial area (Mean ± S.D., n = 149)	Mean ratio (Industrial to non-industrial area)
Formaldehyde	3.62 ± 1.82	3.41 ± 1.69	1.06
Acetaldehyde	5.46 ± 7.88	2.20 ± 1.10	2.48 *
Acetone+Acrolein	3.59 ± 1.92	2.71 ± 1.50	1.33 *
Propionaldehyde	0.91 ± 1.09	1.12 ± 1.26	0.81
Methyl ethyl ketone	3.19 ± 3.15	1.76 ± 1.19	1.82 *
Butyraldehyde	0.30 ± 0.40	0.26 ± 0.34	1.16

^*Industrial and non-industrial groups are significantly different at a level of 0.05 by Mann-Whitney test.