Add To Favorites In PHR
Experts explain bacteria indicator, possible alternative
Hawaii Tribune-Herald - 7/17/2017
KAILUA-KONA - While signs have been posted at some beaches in recent months warning beachgoers of high bacteria levels in the water, those counts don't necessarily mean waters are contaminated with sewage.
That's because the type of bacteria the feds recommend states rely on to indicate pathogens in the water grows naturally in Hawaii's soil, where it can be washed into coastal waters by rainfall, experts say.
That indicator bacteria, enterococci, typically doesn't cause illness in people.
Meanwhile, the state's Clean Water Branch has additional tips to keep water users safe and healthy, such as avoiding stream mouths and turbid waters that can carry dangerous pathogens and washing thoroughly after swimming at the beach.
The branch is required under federal law to keep tabs on coastal recreational waters and notify the public and feds when bacteria counts exceed standards, said Myron Honda, environmental health specialist with the Clean Water Branch, which is under the Department of Health.
Hawaii, as recommended by the U.S. Environmental Protection Agency, uses enterococci as a "pathogen indicator" that the EPA says can indicate the potential for someone to get sick.
The EPA provides about $300,000 a year to assist the state with compliance with federal water quality law.
But the bacteria tests come with a caveat: Because enterococci grows naturally in the local soil environment, it doesn't necessarily mean there's sewage in the water.
"From our experience before, it's not due to sewage," said Clean Water Branch Chief Alec Wong.
Challenging enterococci as a benchmark
Enterococci itself isn't considered a pathogen, according to an EPA document that outlined the criteria for recreational water quality standards.
"Most strains of enterococci ? do not cause human illness (that is, they are not human pathogens)," the document stated, "rather, they indicate the presence of contamination."
Because pathogens that can make people sick often accompany these indicators, the feds recommend using standards that rely on those bacterial indicators.
But Hawaii's geography and climate make the island chain a great place for enterococci to grow in the soil.
A project led by Roger Fujioka at the University of Hawaii at Manoa in the early 2000s challenged two assumptions about the value of fecal indicator bacteria, such as enterococci, as standards for Hawaii water quality. The study was based on data showing that all of Oahu's streams consistently exceeded federal standards for indicator bacteria.
The first assumption was that there weren't any "significant environmental sources" of the bacteria. If true, that would mean its presence would have to be the result of sewage or animal feces, according to an abstract of the study. The second was that fecal indicator bacteria "cannot multiply under natural environmental conditions."
As to the first, the study found that soil in Hawaii is a "natural habitat for fecal indicator bacteria."
"Moreover, rain, which is the source of water for all streams, will transport these soil-bound fecal indicator bacteria to all streams," researchers wrote. "Thus, soil rather than sewage or feces of animals is the major source of fecal indicator bacteria recovered from all streams of Oahu."
Furthermore, the research found that the state's soil environment is well-suited for the enterococci to multiply. Critically, significant pathogens found in sewage that can cause illness can't multiply under those same conditions. That means if the indicator bacteria grow, their numbers don't represent the amount of sewage or fecal contamination and don't show the risk of transmitting pathogens that can make people sick.
There is another option for sewage indicators: Clostridium, another sort of bacteria, which Fujioka's research identified as an alternative indicator with one big advantage. It doesn't grow in the soil and is "consistently present in high concentrations in sewage."
Honda said clostridium "is a little bit better" as an indicator and, "though not ideal," could be used in tandem with enterococci.
"I think you need to use them together," he said.
The EPA though has said that the branch can collect data on clostridium, but not do much else.
"EPA said we can no longer take action based on that, because it's not a national standard," said Honda.
To be able to use clostridium as a standard, Honda said, they would need to be able to show the illness risk, which hasn't been done.
The EPA has said that when states adopt new or revised criteria as part of their standards, "they must be scientifically defensible," according to the agency's recreational water quality criteria, adding that states must establish numerical values based on federal regulations.
"For us to do an epidemiological study, I mean, it's like in the millions of dollars," Honda said.
That's because it would require the state to do a study on a massive scale, looking at a beach-going population and a control population, following both for any illnesses.
"It's really involved and definitely not something that we can do in the department," he said, "this is something like EPA-level."
Numbers behind tests
When it occurs, illess typically comes as a result of ingesting contaminated water and cases are typically gastrointestinal in nature. It carries symptoms like nausea, vomiting, stomachache and fever, among others.
Those particularly at risk include children, the elderly, pregnant women and those with weakened immune systems. Enterococci is not an indicator of other pathogens like staph, Honda added.
Quality standards have a threshold of an average of 35 colony-forming units per 100 milliliters over any 30-day period, but the state branch will also take action if any single measurement exceeds 130 colony-forming units per 100 milliliters.
That's the point at which the EPA pegged its estimated illness rate at 36 per 1,000 people.
State beaches are tested at different rates based on their division into three tiers. Those tiers are based on factors such as economic and social importance, said Honda.
Tier 1 beaches are the state's "core beaches," which are tested every week. There are 50 of those beaches statewide, 12 of which are on Hawaii Island. Kahaluu Beach Park, Kamakahonu Beach and Anaehoomalu Bay are considered Tier 1 beaches.
Tier 2 beaches, which include Hapuna Beach State Recreation Area and Hookena Beach Park, are monitored less frequently, and Tier 3 beaches are not routinely monitored.
When tests show bacteria levels in excess of the standards, the agency puts up temporary signs, advising people in the area that bacteria levels exceed the standard and that there could be health risks associated with swimming in the water.
Testing continues daily until bacteria levels fall back below the threshold. That typically happens almost immediately.
"Almost every instance where we had to post a sign, it came down the following day, including here," Honda said.
At sites where bacteria levels are consistently above the threshold, the agency sets up permanent signs. That hasn't yet happened on the Big Island.
In any case, the beach remains open. Honda said they don't have the authority to shut down a beach.
Bacteria counts and advisories are available at http://health.hawaii.gov/cwb/.