The primary public health concerns associated with Lake Tahoe's nearshore are (1) harmful algal blooms; and (2) fecal indicator bacteria concentrations, which indicate the possible presence of pathogens and viruses which can make people sick.
The first known harmful algal bloom (HAB) occured in the Lake Tahoe Keys in August 2017. The level of measured cyantoxins was below any health concern, but the area was posted to protect pets. The Lahontan Water Board continues to monitor Lake Tahoe for HAB issues and responds to reports of possible HABs by sampling the lake and posting results as appropriate.
The most recent fecal indicator bacteria monitoring using Escherichia Coli (E. coli) was conducted in 2024 between June and September at eight recreational beaches around Lake Tahoe. Results of from 2024 monitoring is available below. E. coli monitoring is underway for the 2025 summer recreation season, results will be posted as they are received.
No Monitoring Programs are yet associated with this Focus Area.