Table 1. Demographic characteristics of the participants.

Age groups	High-polluted area (n = 436)		Low-polluted area (n = 225)		Control area (n = 249)
	M	F	M	F	M	F
40–44	6	21	4	9	6	17
45–49	22	30	6	12	9	23
50–54	33	51	16	25	8	18
55–59	22	32	19	23	14	13
60–64	45	44	23	25	33	30
65–69	42	47	18	23	27	33
70–75	18	23	10	12	12	6
Total	188	248	96	129	109	140