Sarah Cheshire translates public health into practical rules for the water, where trends move fast and risks move faster.
As an environmental health scientist at the Utah Department of Health and Human Services, and formerly a local health inspector, she has specialized in pools and spas during a time when they’re evolving into wellness experiences with new systems, new users, and new risks.
Take cold plunges and manmade swimming lagoons, for example. Both promise wellness and novelty while living in regulatory gray zones where old rulebooks don’t quite fit. Cheshire’s goal is to protect public health while allowing these new experiences to serve the bathing public.
“We’re trying to figure out what’s the line, where’s the limit — what’s safe — but still allow people to enjoy them,” she says.
NOVEL BUT SAFE
Cold plunges are surging in popularity, whether they be single-person tubs or larger vessels to accommodate larger bather loads, such as those for athletic teams.
Utah has become an early test case in how to regulate these water bodies. A proposed rule has been published and remains a work in progress, but it signals what other jurisdictions may consider: signage acknowledging health risks; age and depth limits similar to spa-style guardrails; frequent testing; secondary sanitation; and an emphasis on showers and hygiene.
Cold water also changes the treatment conversation. Many plunges involve “contrast” use — hot to cold — bringing a high organic load. Disinfectants may not react as quickly in cold water, Cheshire notes, which is driving interest in supplemental treatment such as ozone and UV to add an additional layer of protection.
Then there’s the physiological reality. Cold shock can trigger a fight-or-flight response. “Heart attacks can be triggered,” Cheshire says, and people with arrhythmias or other underlying factors may face higher risk.
She is working to learn more about the impacts and how to respond.
Cheshire’s work extends beyond Utah through the Model Aquatic Health Code (MAHC), where she has served in leadership and now participates in a committee focused on cold plunge pools.
As the category grows, Cheshire is also watching what cold water does to systems and equipment. NSF/ANSI 50 has long guided pool and spa equipment standards, but coldwater operation raises questions about saturation index, corrosion, and durability — issues the MAHC community has flagged for further examination.
REGULATING LAGOONS
Manmade swimming lagoons, with their crystal-clear water and ample room for recreation, are another amenity defying classification.
“They’re not lakes, but not pools,” Cheshire says, which is why enforcing standard pool codes can feel like fitting “a round peg in a square hole.”
Their sheer scale changes everything: turnover and treatment aren’t managed the same way as in a traditional commercial pool, and the water often supports multiple uses beyond swimming. In 2024, Utah passed a rule specifically regulating manmade lagoons using a performance-based approach — set public-health outcomes, then allow different technologies and designs to meet them. Some systems rely on sand filtration; others push and circulate water so the designated bathing zone turns over more quickly. The rule also emphasizes clear zoning and bathing areas, plus patron hygiene — especially showers — to manage bather load and reduce contamination.
Cheshire’s influence also runs through industry standards. With the Pool & Hot Tub Alliance (PHTA), she serves on the committee for Standard 11 on water quality, helping reorganize it for easier usability.
Across cold plunges and lagoons, her throughline is practical: Ask who’s using the water, how often, and under what conditions, then write rules and standards that keep pace.
“It’s an evolving regulation — we put something in place, now we have to evolve.”
