NRAP Focus Area
Focus Area - Public Health
Basics
Focus Area - Public Health
Human interactions with nearshore waters are primarily associated with
recreational activities and with consumption of treated and untreated waters drawn from the lake. The characteristics and quality of water used for consumption are regulated under separate state and U.S. EPA provisions. Existing state and local programs for tracking presence of harmful micro-organisms and toxic compounds serve as nearshore human health indicators.

Ultra-oligotrophic lakes do not generally have issues with toxicity or harmful microorganisms, unless there are discharges of sewage or waste. Sewage and industrial discharges are not allowed into Lake Tahoe, although surface stormwater runoff to the lake from urban areas and some recreational activities could conceivably contribute toxic chemicals or pathogens.
NRAP Focus Area Key Photo
State of Knowledge

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. 

Findings

No Monitoring Programs are yet associated with this Focus Area.