Arsenic Poison in Water: Chart One
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Arsenic Levels in Tap Water Systems in 25 States-
Low and Best Estimates
Average Arsenic Level
(in ppb) |
Low Estimate* of Number of Water Systems Affected |
Low Estimate* of Total Population Served |
Best Estimate** of Number of Water Systems Affected |
Best Estimate** of Total Population Served |
| None detected |
15,624 |
40,619,400 |
15,624 |
40,619,400 |
| Detected, <1* |
2,068 |
28,017,372 |
884 |
5,925,297 |
| > 1 and <3 |
2,935 |
19,994,024 |
3,146 |
25,711,312 |
| > 3 and <5 |
1,321 |
7,440,564 |
1,947 |
17,494,651 |
| > 5 and <10 |
1,348 |
5,033,538 |
1,652 |
10,611,259 |
| > 10 and <15 |
535 |
1,451,616 |
566 |
2,075,157 |
| > 15 and <20 |
251 |
243,526 |
258 |
340,284 |
| > 20 and <25 |
171 |
269,393 |
173 |
270,332 |
| > 25 and <50 |
280 |
354,802 |
283 |
376,542 |
| > 50 |
66 |
99,736 |
66 |
99,736 |
| TOTAL |
24,599 |
103,523,971 |
24,599 |
103,523,970 |
TOTAL at or above 1 ppb
(0.5 ppb presents the highest cancer risk EPA traditionally allows in tap water) |
6,907 |
34,887,199 |
8,091 |
56,979,263 |
*The low estimate is based on the assumption that any nondetect, no matter what the reporting limit, contained no arsenic, even if other samples showed arsenic was present. This highly conservative analysis results in a large number of systems having average concentrations below 1 ppb, because all reported nondetects, no matter what the reporting limit, are averaged as zero. See the discussion in the text for more details on how these averages were calculated.
** The best estimate is the estimated mid-average level of each system, which is the average of the detected levels of arsenic and, for those systems for which there was at least one detect of arsenic, one-half the level of detection for all nondetects. See the discussion in the text for more details on how these averages were calculated. |
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