Bromoform
Norwalk Water Supply
Bromoform, one of the total trihalomethanes (TTHMs), is formed when chlorine or other disinfectants are used to treat drinking water. Bromoform and other disinfection byproducts increase the risk of cancer and may cause problems during pregnancy. Click here to read more about disinfection byproducts.
Samples
Samples exceeding legal limit (MCL)
Samples exceeding
health guidelines
Testing results - average by year
| Year | Average result | Samples taken | Detections | Range of results |
|---|---|---|---|---|
| 2014 | 0.888 ppb | 8 | 3 | ND - 2.90 ppb |
| 2015 | ND | 8 | 0 | ND |
| 2016 | 0.525 ppb | 8 | 2 | ND - 2.20 ppb |
| 2017 | 0.400 ppb | 8 | 3 | ND - 2.00 ppb |
| 2018 | 1.51 ppb | 8 | 7 | ND - 3.40 ppb |
| 2019 | 1.29 ppb | 8 | 8 | 0.500 ppb - 3.60 ppb |
ppb = parts per billion
State and national drinking water standards and health guidelines
EWG Health Guideline 0.5 ppb
The EWG Health Guideline of 0.5 ppb for bromoform was proposed in 2018 by the California Office of Environmental Health Hazard Assessment as a one-in-a-million lifetime risk of cancer. Values greater than one-in-a-million cancer risk level can result in increased cancer cases above one in a million people.
ppb = parts per billion
All test results
| Date | Lab ID | Result |
|---|---|---|
| 2014-01-20 | 2029772 | 2.20 ppb |
| 2014-01-20 | 2029771 | 2.90 ppb |
| 2014-04-17 | 2048110 | ND |
| 2014-04-17 | 2048109 | ND |
| 2014-07-09 | 2061020 | ND |
| 2014-07-09 | 2061021 | ND |
| 2014-10-03 | 2081948 | 2.00 ppb |
| 2014-10-03 | 2081949 | ND |
| 2015-01-15 | 293418 | ND |
| 2015-01-15 | 293419 | ND |
| 2015-04-27 | 297403 | ND |
| 2015-04-27 | 297402 | ND |
| 2015-07-09 | 300560 | ND |
| 2015-07-09 | 300561 | ND |
| 2015-10-06 | 306750 | ND |
| 2015-10-06 | 306751 | ND |
| 2016-01-14 | 310292 | ND |
| 2016-01-14 | 310291 | ND |
| 2016-04-14 | 313257 | ND |
| 2016-04-14 | 313258 | ND |
| 2016-07-11 | 316662 | 2.20 ppb |
| 2016-07-11 | 316663 | 2.00 ppb |
| 2016-10-19 | 320319 | ND |
| 2016-10-19 | 320318 | ND |
| 2017-01-25 | OE474372 | 0.600 ppb |
| 2017-01-25 | OE474371 | 0.600 ppb |
| 2017-04-12 | 326227 | ND |
| 2017-04-12 | 326228 | ND |
| 2017-07-13 | 329599 | ND |
| 2017-07-13 | 329600 | 2.00 ppb |
| 2017-10-24 | 333711 | ND |
| 2017-10-24 | 333712 | ND |
| 2018-01-18 | 336815 | 3.30 ppb |
| 2018-01-18 | 336814 | 3.40 ppb |
| 2018-04-18 | 339815 | 0.400 ppb |
| 2018-04-18 | 339816 | 0.300 ppb |
| 2018-07-11 | OE681740 | 1.000 ppb |
| 2018-07-11 | OE681741 | 1.10 ppb |
| 2018-10-17 | OE728415 | 2.60 ppb |
| 2018-10-17 | OE728416 | ND |
| 2019-01-24 | 349702 | 0.800 ppb |
| 2019-01-24 | 349703 | 0.800 ppb |
| 2019-04-18 | 352496 | 0.500 ppb |
| 2019-04-18 | 352497 | 0.500 ppb |
| 2019-07-17 | 355880 | 2.80 ppb |
| 2019-07-17 | 355881 | 3.60 ppb |
| 2019-10-23 | 359408 | 0.700 ppb |
| 2019-10-28 | 359553 | 0.600 ppb |