It seems like a straightforward question: Do the tons of toxic material the Los Angeles County fires sent spewing into the ocean pose an ongoing threat to human health?

For nearly five months, public agencies, advocacy groups and scientists have analyzed samples of seawater and sand in an attempt to determine whether January’s catastrophe has made it less safe to swim, surf or sunbathe at the region’s famous beaches.

Their collective results point to two broad truths.

The first is that neither government agencies nor privately funded groups have found levels of fire-related contamination in sand or ocean water likely to pose health risks to beachgoers. While visible fire debris still occasionally washes up on shore and should be avoided, public health officials and advocates say, there is little evidence of fire-related toxins high enough to sicken visitors through casual recreational exposure.

The second is that the unprecedented amount of ecological damage January’s firestorms caused simply dwarfs the tools we have available to measure beach pollution.

The seawater safety testing that informs the county’s beach water quality advisories is designed to look for hazards posed by sewage, not fire debris.

State and federal regulators have clear guidelines on the maximum amount of heavy metals and chemicals that can be in our drinking water before it is deemed unsafe, but no similar standards for how much of this stuff it is safe to be exposed to when swimming.

This lack of preexisting health guidelines has made it hard for public health officials to describe the situation at the coast in simple, declarative terms. That, in turn, has frustrated a public that just wants to know if it’s safe to get back on a surfboard.

“There are no human health standards for recreating in water or on sand that has been contaminated, potentially, by these pollutants … and so there’s no straightforward way to test for contaminants and then [say] this exceeds the risk threshold, or it doesn’t,” said Tracy Quinn, president of the environmental nonprofit Heal the Bay. “And that has presented a lot of challenges.”

The Palisades and Eaton fires incinerated more than 40,000 acres and countless tons of plastics, electronics, building materials, batteries and other potentially hazardous materials. Because of the region’s geography, much of that toxic ash and residue eventually flushed into the ocean.

County health officials closed several miles of coastline entirely in January and February, citing spiking levels of bacteria caused by destroyed sewage systems and dangerous amounts of hazardous debris clogging up the shore.

In the meantime, the Los Angeles Regional Water Quality Control Board began collecting samples of ocean water to assess contaminant levels.

The board soon had reams of public data for beaches from Las Flores Creek in Malibu to Dockweiler Beach in Playa del Rey, showing results for dozens of different contaminants, including heavy metals, polychlorinated biphenol and polycyclic aromatic hydrocarbons.

But, again, there are no established regulations for how much of these contaminants a surfer or swimmer can be safely exposed to. There also isn’t much historical data with which to compare the current amounts of pollutants such as plasticizers, fire retardants and other modern chemicals to pre-fire conditions.

As a result, county health officials struggled to translate their findings into recommendations the public could use.

“This is not business as usual with ocean water testing,” said Dr. Nichole Quick, chief medical advisor with the L.A. County Department of Public Health.

County health officials spent hours plugging the numbers into a publicly available Environmental Protection Agency tool that helps evaluate safe environmental exposure levels to various substances. They also invited experts from other agencies to weigh in.

No matter how they ran the numbers, they didn’t see evidence that the levels of contaminants present in January and February would threaten human health.

Heal the Bay tested seawater around the same time. The group found enough lead and other heavy metals in some samples to potentially build up over time in the tissue of marine life, but not high enough to sicken a human swimming in those waters.

The county now has an online dashboard for post-fire environmental data that includes ocean water testing.
But by the time it went live this spring, many members of the public were already frustrated by the lack of clear-cut answers and the confusing pile of data online, said Eugenia Ermacora, Los Angeles chapter manager for the Surfrider Foundation.

“It creates this anxiety,” she said. “Everybody wants an answer right now: Is it safe? Me too! I’m a surfer. My fins are drying. But we’re trying to be patient at the same time.”

L.A.’s coastal ecosystem is now the subject of a massive real-life science experiment. As in all sweeping studies, it will be a while before clear answers emerge. In the meantime, advocates are hopeful that L.A.’s experience now will help communities respond to disasters in the future.

“This is not the last time we’re going to see an urban megafire in a coastal city. It may not be the last time we see an urban megafire in Los Angeles, and we need to be better prepared,” Quinn of Heal the Bay said. “My hope is that we take the information that we’re learning here and we create protocols and standards for what to do next time.”

A group of environmental researchers is calling on the Newsom administration to step in and pay for soil testing at thousands of homes destroyed in the Eaton and Palisades wildfires.

Nearly a dozen university professors wrote a letter Wednesday to Gov. Gavin Newsom and California Environmental Protection Agency Secretary Yana Garcia, imploring state officials not to abandon California’s wildfire-recovery protocols, namely the long-standing policy to conduct soil sampling at destroyed homes after cleanup crews finish removing toxic ash and a layer of topsoil.

Because federal disaster agencies have repeatedly refused to conduct soil sampling to ensure burned-down homes do not contain unhealthy levels of toxic substances, the researchers argue it is imperative for the state to intervene in the ongoing recovery efforts for the Palisades and Eaton wildfires.

“At present, no parcel-specific soil testing is required or recommended by the State for residential properties impacted by the Eaton Fire and Palisades Fire,” the letter reads. “In our view, this poses a serious risk to public health and the economic recovery of the communities.”

The letter was signed by faculty members from nine universities, including USC and UCLA, many of whom are currently involved in conducting free soil testing for homeowners in and around the burn zones of the January wildfires. Among them, Andrew Whelton, a Purdue University professor who has investigated contamination following wildfires, said comprehensive soil testing was paramount to the health and safety of the fire-affected communities.

“The decision not to conduct soil testing the way it has been in the past — without any advanced warning — has really thrown personal safety and the ability of the community to rapidly recover up in the air,” Whelton said.

State officials said federal authorities are in charge of the wildfire recovery effort, including the decision on soil testing and remediation. State officials had asked FEMA to reconsider paying for soil testing, but the request was rejected within hours.

“The State continues to push for our federal partners to conduct comprehensive soil sampling as part of the debris removal process,” said Nefretiri Cooley, a spokesperson for CalEPA.

The university researchers highlighted recent soil testing efforts by the Los Angeles Times and the Los Angeles County Department of Public Health that found elevated lead and arsenic levels at destroyed homes cleared by federal debris removal crews in Altadena.

The Army Corps of Engineers, the agency supervising debris removal crews, declined to comment on the county results. A FEMA spokesperson said the agency still maintains that its cleanup approach — removing wildfire debris and up to 6 inches of topsoil — is sufficient to remove immediate public health risks.

The L.A. County Health Department has allocated up to $3 million to pay for soil testing, mostly for homeowners who showered in toxic smoke and ash downwind of the Eaton fire. But Whelton said these efforts on their own are not sufficient to analyze the risk.

“One soil sample will be analyzed that a homeowner submits to a commercial laboratory, and then the homeowner will have to interpret the data on their own and decide what to do,” Whelton said. “So that is not going to get people [back] to safe properties again.”

A worker clears debris from a home destroyed in the Palisades fire in Pacific Palisades in April.

(Genaro Molina / Los Angeles Times)

Local officials continued to emphasize the need for a speedy recovery, in part because they are worried about the precipitous drop in tax revenue. Federal, state, and local governments could experience tax revenue losses from roughly $730 million to $1.4 billion due to the wildfires, according to the Los Angeles County Economic Development Corporation, a nonprofit focused on economic growth.

At a meeting earlier this week, L.A. County officials announced that a new program is expected to allow licensed architects and engineers to “self-certify” that residential rebuilds meet building code requirements, with the assistance of artificial intelligence software that reviews building plans. The initiative aims to significantly speed up the timeline for issuing building permits.

More than 10,000 properties were signed up to be cleaned by federal debris removal crews. So far, they’ve cleared around 4,700 properties, which are now eligible for rebuilding permits without soil testing.

In the past, disaster agencies soil testing at cleaned-up properties to ensure toxic substances did not exceed California’s standards for residential properties. At properties where toxic substances were found above state standards, disaster agencies ordered cleanup crews to return to remove more soil and perform additional testing.

If state officials walk away from their soil-testing policy, some environmental experts say hundreds of homes in Altadena and the Pacific Palisades will still be contaminated, potentially exposing returning residents to toxic metals, like lead. But perhaps more worrying, it could also set a precedent for California communities devastated by wildfires in the future.

In California, where 30% of the state’s population lives in high-risk fire zones where buildings intermingle with wilderness, destructive wildfires are inevitable. But after the Eaton and Palisades fires, many homeowners are confused about federal and state agencies’ responsibilities during disaster cleanup.

“It is certainly appropriate to have discussion about who’s responsible for soil testing and soil remediation after these wildfires,” Whelton said. “But because there was an abrupt decision by multiple government agencies to just not do it, that’s left a whole bunch of property owners with anxiety and an unclear path to how they’re going to make their property safe again — or if they want to return.”

During an interview in late April with Dr. Phil, Robert F. Kennedy Jr. reiterated his appeal to parents on vaccine safety: “We live in a democracy, and part of the responsibility of being a parent is to do your own research.”

The U.S. health secretary has also announced his own investigation, pledging to find an answer to the autism “epidemic” by September. It’s an ambitious goal. It’s also a realistic one but only if he already has an answer in mind.

To tell the story you want with statistics, you don’t have to lie or fabricate data — though that happens, too. More often, statistics are manipulated, figures massaged and results skewed through subtler means. Sometimes, it’s sloppiness or unconscious bias at work. Other times, the distortion is deliberate.

Whether the numbers attempt to tell a story about the economy, immigration, education or public health, we should empower ourselves to recognize the deception.

Vaccine data are far from immune to statistical trickery and its consequences.

Not only might individuals skip a vaccine and get unnecessarily sick, but the viral spread of misinformation can poke holes in the herd immunity needed to protect a population. One new, untampered statistic tells a chilling story: A meager 10% drop from today’s already dangerously low measles vaccination rates could spark an estimated 13-fold increase in annual cases.

Statistics wield incredible power. I developed a deep respect for them during my first career as a biostatistician. Today, as a journalist, I see numbers leveraged for good and for bad. I’ve seen them help the public and policymakers interpret complex data, detect patterns and make better decisions — evidenced in my reporting on data dashboards during the COVID-19 pandemic. I’ve also seen data withheld and statistics doctored for less-than-noble aims by chemical companies, the gun industry, police departments, the U.S. military, climate change deniers and vaccine skeptics, to name a few.

If left unaware of the deceit, the public can’t hold these groups accountable. And if citizens base their votes and other decisions — like whether to vaccinate their child — on distorted or false information, our democracy and our health lose again.

Fortunately, inoculation against misinformation is available. As Kennedy and his collaborators dig into vaccine and autism data, as measles cases mount, and as you “do your own research” or simply digest your news and social feeds, here are five red flags to watch for.

Chance

The infamous paper that launched the vaccine-autism controversy was based on just 12 children. Its author claimed that eight showed signs of developmental regression after receiving the measles-mumps-rubella vaccine. The study was later retracted for scientific misconduct. But even without fraud, the sample size should raise alarm. Chance alone could explain such a small cluster of cases. Contrast that with rigorous studies — like one in Denmark with more than 650,000 participants — that consistently find no relationship between the MMR vaccine and autism.

We should be just as wary when studies test a grab bag of possible outcomes. Suppose researchers ask whether a vaccine causes heart disease, diabetes, any of a dozen types of cancer or any of five neurodevelopmental disorders. Even if the vaccine is in reality not affecting any of those 20 outcomes, when researchers try to study so many things all at once, statistical noise can mean one may erroneously appear “significant” just by chance. A more rigorous and targeted study would be far less likely to give that false positive.

Count quality

Big numbers can impress. But quality counts. In 2021, the Delphi-Facebook survey estimated near real-time COVID-19 vaccine uptake using weekly responses from around 250,000 people. On paper, the large sample size conveyed statistical confidence. But in practice, the data missed the mark. The sample was biased and unrepresentative of the overall population. By late May, the study had overestimated vaccine uptake by a wide margin — 70% compared with the true rate of 53%. That inflated figure may have lulled the public and policymakers into a false sense of security.

Beware, too, of the misuse of raw data. Figures from the Vaccine Adverse Event Reporting System appear in many papers and posts asserting vaccine harms. But this system was set up only as an early warning system. Anyone can submit a report on a suspected reaction. If a hint of a pattern emerges, then researchers will investigate to determine if the signal represents an actual risk. As its own website warns, the initial reports may be “incomplete, inaccurate, coincidental, or unverifiable.” People may be apt to connect an event that occurs shortly after vaccination with the shot itself, for example, especially if they personally fear the safety of vaccines. To demonstrate the system’s fallibility, a doctor filed a report saying he turned into the Incredible Hulk after receiving a flu vaccine. The entry was initially accepted into the database.

Cherry-picking

One study circulating in the anti-vax community was led by David Geier, the same figure tapped by Kennedy to head his federal autism and vaccine investigation. The study found a connection between autism and vaccines containing the preservative thimerosal. But it hinges on a critical flaw: Cases of autism and the comparison group came from different time periods. Because vaccination rates changed dramatically over time, the design introduced a spurious association.

Among myriad ways to manufacture a desired conclusion is the strategic choice of time frame, analysis method or how the data are presented. By plotting only convenient variables or truncating inconvenient values, for example, you can tell the story of your choosing. One COVID-era graph appeared to show that vaccines did not prevent deaths. The trick? It compared vaccine uptake with cumulative deaths — a number that can only rise over time, and so of course would broadly move in the same direction as the uptake rate of a desperately needed new vaccine that the public is clamoring for.

Another sleight of hand to play down the size of a problem: Acknowledge a not-so-unusual number of outbreaks while ignoring how large or how deadly those outbreaks were, just as Kennedy did in February with measles.

Correlation vs. causation

A widely shared study recently referenced by Kennedy reports a link between vaccination and neurodevelopmental disorders among 9-year-olds in Florida. This one, too, is riddled with problems — namely, its failure to account for other factors that could explain the results. Children whose parents more regularly use the healthcare system, for example, are more likely to get both vaccinated and diagnosed. Healthcare engagement confounds the relationship. So, we can’t say the vaccine caused neurodevelopmental disorders any more than we could say that increased consumption of margarine resulted in a higher divorce rate in Maine. These are cases of correlation, not causation.

Something similar and even more interesting cropped up when people compared death rates by COVID-19 vaccination status. At first glance, an unexpected pattern emerged: The vaccinated were dying at about twice the rate of the unvaccinated. The catch here? The analysis didn’t account for age. Older people were more likely both to die and to get vaccinated. Once researchers broke the data down into age groups, a more accurate — and reverse — picture emerged: The unvaccinated were dying at higher rates.

Context and conflicts

Talk of an uptick in autism diagnoses often skips crucial context: expanded awareness, broader diagnostic criteria and financial incentives for diagnosis. There could well be a surge in the number of cases without any surge in the true incidence of the disorder.

Also, discussions motivated by a desire to explain autism or to oppose vaccines tend to omit the robust studies that have debunked any link between vaccines and autism — because those would be unhelpful to the agendas. Vaccine opponents may further ignore the glaring conflicts of interest behind many of the studies still pushing that autism narrative. Geier had a study retracted, in part, for not disclosing his involvement in vaccine-related litigation.

Conflicts of interest surround Kennedy as well. He has spent years pushing anti-vaccine claims despite overwhelming evidence of vaccine safety and despite not being a doctor or a scientist. Now that he is in a position of authority over public health, he should at least be held to the same ethical standards as a scientist. Modern scientific practice calls for statisticians to specify their hypotheses and analysis plans before data are collected. This ensures transparency and objectivity, and reduces the risk of data dredging and misleading results. Statisticians follow where the data lead rather than mold or seek out data to fit a predetermined narrative.

Kennedy’s team appears to be following a different playbook. According to a former top vaccine official, Kennedy’s team requested a wish list of data seemingly to justify their autism theory: The team asked for cases of brain swelling and deaths caused by the measles vaccine. The official said there are no such cases. Someone who keeps hunting for evidence to back up his discredited theory is not conducting science.

Our stories should be malleable. Our statistics should not.

Lynne Peeples, a science writer, is the author of “The Inner Clock: Living in Sync With Our Circadian Rhythms.”