Hydrogen sulfide and odors in Tijuana River Valley outdoor air can negatively affect people's health

Media Advisory

ATLANTA, GA — The Agency for Toxic Substances and Disease Registry (ATSDR) today released its report, Health Evaluation of Hydrogen Sulfide in Outdoor Air in the Tijuana River Valley, for public comment.

For decades, untreated wastewater has flowed from Tijuana, Mexico, across the U.S. border and into the Tijuana River Valley and Pacific Ocean. This wastewater contains hydrogen sulfide, which has a foul, rotten-egg odor. The California congressional delegation asked ATSDR to investigate the impact of wastewater contamination in the Tijuana River Valley on nearby communities.

The full report and a summary factsheet are available in English and Spanish at: https://wwwn.cdc.gov/TSP/PHA/PHAListing.aspx?StateIndicator=CA.

Virtual public meeting

ATSDR scientists will discuss the report's findings and answer questions at a virtual public meeting:

How to submit public comments

The public is invited to submit comments to ATSDR by November 21, 2026:

Email comments to: OCHHAPublicComment@cdc.gov

Or mail comments to: Agency for Toxic Substances and Disease Registry Attn: Records Center 4770 Buford Highway NE, MS S106-5 Atlanta, Georgia 30341

For more information

For more information about ATSDR's work in the Tijuana River Valley, contact CDC-INFO at 1-800-CDC-INFO (1-800-232-4636) or www.cdc.gov/info or visit www.atsdr.cdc.gov.

Next steps

ATSDR will revise this report on hydrogen sulfide in air in response to public comments and release a final version. ATSDR also plans to release a second report about chemicals in the surface water, sediment, and soil.

For members of the media: If you have questions, please fill out the request for comment form at this HHS link: https://www.hhs.gov/request-for-comment-form/index.html?Agency=CDC

ATSDR, a federal public health agency of the U.S. Department of Health and Human Services, invests in everyone's health by evaluating the potential for adverse human health effects of exposure to hazardous substances in the environment.