Office of Environmental Health Hazard Assessment


Notification Levels are health-based advisory levels for chemicals in drinking water that are established for chemicals for which there are no formal regulatory standards (Maximum Contaminant Levels, or MCLs). Notification Levels may be established by the Department of Public Health Division of Drinking Water and Environmental Management (DDWEM) when a chemical is found in or threatens drinking water sources. Upon request by DDWEM, OEHHA performs a risk assessment of the chemical using standard risk and exposure assumptions and proposes a health-protective level. A notification level is then established by DDWEM, and amended as necessary as conditions or risk assessment methods change. The OEHHA letters to DDWEM, which provide brief summaries of the toxicological literature and proposed Notification Levels, can be accessed through the links below.

When notification levels are exceeded, the drinking water system is required to notify the local governing body of the local agency in which the users of the drinking water reside. If the notification level is exceeded, the Department of Public Health (DPH) recommends that the utility also inform its customers and consumers about the presence of the contaminant and about the health concerns associated with its exposure. Response levels are levels of the contaminant at which DPH recommends the drinking water system take the affected water source out of service. These levels range from 10 to 100 times the notification level depending on the chemical. Further information on notification and response levels can be found at the DHS Web site at The California legislation covering notification and response levels is Health and Safety Code 116455 and can be found at Chemicals on the DDWEM Notification Level list that are not covered by an OEHHA document were developed by DDWEM from other information sources.

(view html files)

Notification Level (ug/L)

Download pdf file

1,2,3-trichloropropane 0.005 53kb
1,2,4-Trimethylbenzene (1,2,4-TMB) and 330 171kb
1,3,5-Trimethylbenzene (1,3,5-TMB) 330 same as above
1,4-Dioxane 3 91kb
2-Chlorotoluene 140 143kb
Carbon Disulfide 160 93kb
Chlorate 800
updated by DHS as described here
Methyl Isobutyl Ketone 120 141kb
Naphthalene 17
updated by DHS as described here
n-Propylbenzene (isocumene) 260 171kb
sec-Butylbenzene and 260 170kb
tert-Butylbenzene 260 same as above
Tertiary butyl alcohol (TBA) 12 178kb
Vanadium 50
updated by DHS as described here
Flex Your Power Website
Energy efficiency and conservation information. Find incentives/rebates, technical assistance, retailers, product guides, case studies and more.
AMBER ALERT: Save a Child Amber Alert logo
AMBER ALERT empowers law enforcement, the media and the public to combat abduction by sending out immediate information.