|  | Cases | Controls |  | ||
---|---|---|---|---|---|---|
How much does ... contribute to breast cancer? | No. | % | No. | % | Â | |
Heredity | A lot | 331 | 42 | 474 | 66 | ** |
 | A little | 295 | 37 | 163 | 23 |  |
 | Not at all | 99 | 13 | 36 | 5 |  |
 | Don't know | 62 | 8 | 48 | 7 |  |
Diet | A lot | 217 | 28 | 205 | 28 | Â |
 | A little | 327 | 42 | 294 | 41 |  |
 | Not at all | 160 | 20 | 125 | 17 |  |
 | Don't know | 83 | 11 | 97 | 13 |  |
Chemicals and pollutants in the air or water | A lot | 476 | 60 | 412 | 57 | * |
 | A little | 188 | 24 | 203 | 28 |  |
 | Not at all | 53 | 7 | 31 | 4 |  |
 | Don't know | 70 | 9 | 75 | 10 |  |
Women's reproductive or breast feeding history | A lot | 67 | 9 | 70 | 10 | Â |
 | A little | 262 | 33 | 261 | 36 |  |
 | Not at all | 245 | 31 | 225 | 31 |  |
 | Don't know | 213 | 27 | 165 | 23 |  |