Yadira Salcedo was born in Mexico to parents who did not know how to swim. As a child, she nearly drowned when she waded too deep in a backyard pool.

Now a mother of two in Santa Ana, Calif., Ms. Salcedo is “breaking the cycle,” she said, making sure Ezra, 3, and Ian, 1, never experience such terror. The family has qualified for Red Cross scholarships to a new program that teaches children who might not have other chances to learn how to swim.

On a recent day, Ms. Salcedo and her children climbed together into the Salgado Community Center pool, using kickboards and blowing bubbles with an instructor, Josue, who uses a mix of English and Spanish.

Drowning is the leading cause of death for children ages 1 to 4, according to the Centers for Disease Control and Prevention. Deaths are likely to surge this month, as they do every July, with children drowning just feet from their parents without a scream, struggle or splash. A 4-year-old at a Texas hotel pool, a 5-year-old in a California river, a 6-year-old at a Missouri lake and a 10-year-old at an Indiana public pool all drowned just this past week.

And yet, despite calls from the United Nations, the United States is one of the only developed countries without a federal plan to address the crisis. Thirty years of progress in decreasing the number of drowning deaths in the country appears to have plateaued, and disparities in deaths among some racial groups have worsened.

“It’s hard to imagine a more preventable cause of death. No one is going to say, ‘Oh, well, some people just drown,’” said William Ramos, an associate professor at Indiana University School of Public Health-Bloomington and the director of the school’s Aquatics Institute.

“It’s time to go deeper than the sad statistics and answer the ‘why’ and the ‘how,’” he said.

A parent who has never learned to swim yields an 87 percent chance that a child won’t, either, said Dr. Sadiqa A.I. Kendi, the division chief of pediatric emergency medicine at Boston Medical Center, who studies the cyclical nature of injury and inequity.

“This is anthropology,” said Mr. Ramos. “To start a new narrative around water is not an easy task.”

The National Institutes of Health recently published a call for research proposals to examine drowning prevention, writing that “little is known” about what intervention strategies work. The C.D.C. said it planned to do an in-depth analysis of childhood drownings in several states to better understand the contributing factors.

But epidemiologists point to an array of factors that could make it increasingly difficult to close the gap, including shrinking recreation department budgets, a national lifeguard shortage and an era of distraction on pool decks, as parents juggle child supervision with laptops and cellphones when they work from home.

In the longer term, the figures are likely to be exacerbated by climate change, said Deborah Girasek, a drownings researcher at the Uniformed Services University of the Health Sciences. More children are likely to drown in hurricane floodwater in Florida, fall through thin ice in Wisconsin or climb into restricted reservoirs in Yosemite for a reprieve from the increasing heat. (Research shows that drownings rise with every degree on a thermometer.)

Though overall drowning deaths have decreased by one-third since 1990, they have risen by 16.8 percent in 2020 alone, according to the C.D.C. There are still over 4,000 of them in the United States annually, and about a quarter of the deaths are of children. An analysis by the C.D.C. shows that Black children between ages 5 and 9 are 2.6 times more likely to drown in swimming pools than white children, and those between ages 10 and 14 are 3.6 times more likely to drown. Disparities are also present in most age groups for Asian and Pacific Islander, Hispanic, and Native American and Alaska Native children.

Socioeconomic factors are at play as well. A study of drownings in Harris County, Texas, for example, showed that they were almost three times more likely for a child in a multifamily home than in a single-family residence, and that drownings in multifamily swimming pools — like the one at the Salcedos’ apartment — were 28 times more likely than in single-family pools.

Ms. Salcedo said she often saw children swimming in the pool of her apartment complex unsupervised, the gate propped ajar with a water bottle or a shoe.

The leading theory to explain the inequities traces back half a century to the proliferation of municipal pools after World War II. When those gave way to suburban swim clubs and middle-class backyard pools, the historian Jeff Wiltse wrote in his book on pool history, white children began learning to swim in private lessons, while children in minority families saw public pools become dilapidated and aquatics budgets be slashed. Many of the facilities and education programs have never recovered.

Black adults in particular report having had negative experiences around water, with familial anecdotes of being banned from public beaches during Jim Crow-era segregation and brutalized during the integration of public pools.

A U.N. resolution issued in 2021 and a World Health Assembly decision this year to accelerate action urged every member nation to prioritize the fight against childhood drownings. Both the W.H.O. and the American Academy of Pediatrics have implored the United States government to catch up.

“Canada, U.K., Australia, New Zealand, South Africa — they all have a plan. We don’t,” said Mr. Ramos. “The message to Congress is: We need to fix this, and we can. But look at seatbelts, fire safety, smoking cessation. Legislation is what’s going to move the needle.”

Officials could add aquatics to gym class curriculums or mandate four-sided pool fences in backyards (since many victims still wander into pools from the exposed side facing the house). Ms. Girasek said she was eager to see legislation because “we see very clearly that it works.”

After former Secretary of State James Baker’s 7-year-old granddaughter Virginia Graeme Baker was trapped by the suction of a hot tub drain and drowned, a federal law was named in her honor that required public pools and spas to be equipped with drain covers that meet certain standards. It seemed to all but eradicate such deaths.

The U.S. National Water Safety Action Plan, launched by a group of nonprofits last week, is the country’s first-ever attempt to construct a road map to address the crisis. Its 99 recommendations for the next decade serve as a sobering guide through the country’s various gaps in research, funding, surveillance and parental education, compiled by earnest advocacy groups on shoestring budgets that aren’t equipped to fill them alone.

Connie Harvey, the director of the Aquatics Centennial Campaign at the American Red Cross, held a Capitol Hill briefing recently alongside other experts, she said, “to let our leaders know that there is a plan — that this plan exists.”

Representative Debbie Wasserman Schultz, Democrat of Florida and a longtime advocate for drowning prevention, was the only member of Congress to attend.

In the meantime, some local governments have adopted their own interventions. This summer, Seattle is piloting a new initiative based on the nonprofit No More Under, which connects hundreds of low-income and foster children with swim lessons. Broward County, Fla., which has some of the highest drowning rates in the state, is offering free vouchers. And Santa Ana plans to pull more than $800,000 from its Cannabis Public Benefit Fund this year to bring its aquatics program back under its domain.

The city, with a population that is nearly 80 percent Hispanic nestled between wealthier Orange County suburbs, has historically epitomized racial and economic health disparities. One of its public pools is 63 years old. But its Parks and Recreation Department recently hired an aquatics supervisor and 36 new life guards — several of whom the supervisor needed to first teach to swim.

Under the new Santa Ana program, Ms. Salcedo, a waitress, and her husband, a post office employee, who live in a three-generation household, secured scholarships that brought the cost of swim lessons down to $15 per child every two weeks. They plan to attend all summer.

Ezra, who is 3, cried on the first day of lessons. Now he shares facts about hammerheads between strokes during the “Baby Shark” singalong. Ian, the 1-year-old, has not yet mastered walking on land. Still, he paddled after an orange rubber duck, with his mother — now a proficient swimmer — keeping him afloat.

The American practice of setting off fireworks on July 4 stretches back to the first Independence Day celebration in Philadelphia in 1777. Today, it’s a beloved tradition that almost seems impossible to replace.

But with concerns over air quality, wildfires and supply chains, some cities are doing just that.

This year Salt Lake City is replacing its fireworks with synchronized dancing drone displays to avoid worsening air quality and setting off more wildfires. Boulder, Colo., is switching to drones, too, and Minneapolis is opting for lasers, simply because those technologies have been easier to source than fireworks in recent years.

And as wildfire smoke from Canada again blanketed much of the United States last week, New York City officials debated whether to set off fireworks on the 4th but, as of Monday night, had not called them off.

Across the border, Montreal canceled July 1 Canada Day fireworks, citing poor air quality from the more than 100 wildfires burning across Quebec.

“They’re definitely going to compound those existing sources of air pollution,” said Grace Tee Lewis, an epidemiologist at the Environmental Defense Fund who specializes in air pollution and public health.

Fireworks cause a spike in a form of air pollution called particulate matter, the same type of pollution that is elevated from wildfire smoke. While there’s not much research on the risks of fireworks specifically, particulate matter less than 2.5 microns wide (about one-30th the width of a human hair) is known to enter people’s lungs and bloodstreams and cause breathing problems and inflammation. Children, older people and those with existing health conditions like asthma and chronic heart disease should take special care, Dr. Tee Lewis said.

“Watch it from a distance,” she recommended. “The closer you are, the more particulate matter exposure you’re going to have.”

Dr. Tee Lewis added that since the spread of the coronavirus, more people may be more vulnerable to air pollution, especially people suffering from long Covid or heart complications as a result of their infections. For those determined to get their pyrotechnic fix, wearing the same N95 face masks that protect against the virus is one way to protect yourself from smoke and air pollution, she said.

On July 4 and 5, fine particulate matter levels across the country rise by 42 percent on average, according to a 2015 study by the National Oceanic and Atmospheric Administration. Alongside the fireworks party, particulate matter pollution can rise as much as 370 percent.

These levels often exceed what’s allowed by the Environmental Protection Agency for day-to-day outdoor air quality, but local, state and tribal governments are generally allowed to flag one-time events like fireworks, as well as wildfires, as “exceptional events” and avoid officially violating national air standards.

Other countries see similar spikes in air pollution around their own major holidays, said Dian Seidel, an author of the 2015 study and a retired NOAA climate scientist.

Background air pollution from wildfire smoke is certainly something for cities to consider as they plan fireworks or alternative celebrations like drone shows, Dr. Seidel said. “Maybe there are ways not to be a party pooper, but to still have something pretty in the sky to look at, and not cause a big amount of pollution,” she said.

Besides air pollution, fireworks come with other risks. Dogs and other household pets are known to hate July 4, and many humane societies and animal shelters prepare for an influx of lost or runaway pets after the holiday. Fireworks lead to problems for wild animals, too. A 2022 study of wild geese in Europe found that during crucial rest stops on their long migrations, many birds abandoned their sleeping sites on New Year’s Eve.

In 2022, Americans suffered an estimated 10,200 fireworks-related injuries and 11 reported deaths, according to the U.S. Consumer Product Safety Commission. Many of the injuries resulted from smaller firecrackers and sparklers set off by people at home, not during large public or commercial shows.

But the adrenaline rush of sparks, whistles and booms, and a little bit of danger, socially acceptable for one day, is exactly why so many people love fireworks. Even Dr. Tee Lewis said her children set off small July 4 fireworks at their grandparents’ house, where they are legally allowed.

She and Dr. Seidel don’t want to stop the holiday festivities. They simply urge caution, and for people to consider alternatives.

In the end, holiday fireworks lead to just a couple of days of particularly visible air pollution. Around the country and around the world, communities deal with less visible but still unhealthy air daily or seasonally from things like vehicle traffic, industrial pollution and wildfires.

This year, the E.P.A. proposed strengthening its air quality standard for fine particulate matter to better protect public health, but said it would still allow special consideration for “exceptional events.”

The Food and Drug Administration has approved a blood test that can identify pregnant women who are at imminent risk of developing a severe form of high blood pressure called pre-eclampsia, a leading cause of disability and death among childbearing women.

The condition disproportionately affects Black women in the United States and may have contributed to the recent death of Tori Bowie, a track star who won gold at the 2016 Olympics. Two Black teammates of Ms. Bowie — Allyson Felix and Tianna Bartoletta — also developed pre-eclampsia during their pregnancies.

The new test may offer an early warning, identifying which of the many pregnant women who have suggestive symptoms will go on to develop the life-threatening disease within the next two weeks.

“It’s groundbreaking. It’s revolutionary,” Dr. Doug Woelkers, a professor of maternal fetal medicine at the University of California, San Diego, said of the test. “It’s the first step forward in pre-eclampsia diagnostics since 1900, when the condition was first defined.”

To what extent the test will improve outcomes and save lives is not clear, however, as there is no effective treatment for pre-eclampsia, which usually eases after birth.

“We don’t have a therapy that reverses or cures pre-eclampsia other than delivery of the baby, which is more like a last resort,” Dr. Woelkers said.

The new blood test, made by Thermo Fisher Scientific, has been available in Europe for several years. It is intended for pregnant women who are hospitalized for a blood pressure disorder in the 23rd to 35th weeks of gestation.

The test can tell, with up to 96 percent accuracy, who will not develop pre-eclampsia within the next two weeks and so can safely be discharged from the hospital. Two-thirds of the women who get a positive result, on the other hand, will progress to severe pre-eclampsia in that time, and their babies may need to be delivered early.

Distinguishing between the two groups of women is a challenge that has long vexed physicians.

“The warning signs of pre-eclampsia are not very specific,” said Dr. Sarosh Rana, a professor of obstetrics and gynecology at the University of Chicago who has studied the test. “A lot of women will have edema and headaches.” (Edema means swelling.)

“But we don’t really know who among those patients is at higher risk for the really adverse outcomes,” she said.

Pre-eclampsia affects about one in 25 pregnancies, and the incidence has been on the rise in recent years in the United States. The problem usually starts about halfway through a pregnancy, though it can also occur after childbirth. It can lead to a condition called eclampsia, which can lead to seizures and death.

Black women in the United States have pre-eclampsia rates much higher than those of white women, and they are three times as likely as white women to suffer kidney damage or death from pre-eclampsia. Black women are also more likely to lose their babies.

The blood test measures the ratio of two proteins that are produced by the placenta. A study published in NEJM Evidence in November tracked 1,014 pregnant women hospitalized with a hypertensive disorder of pregnancy at 18 medical centers in the United States from 2019 through 2021. Just under one-third were Black, and 16 percent were Hispanic.

The researchers found that the two proteins were greatly unbalanced in the blood of women who developed severe pre-eclampsia. Those with the widest ratios had a 65 percent chance of progressing to severe pre-eclampsia and of delivering their baby within two weeks, either spontaneously or through induction.

“If your levels are among the highest, you deliver in a few days,” said Dr. Ravi Thadhani, an author of the study.

Women who have symptoms suggesting pre-eclampsia but who test negative can be reassured and sent home, but they may need to have the test repeated every two weeks, Dr. Rana said.

Pre-eclampsia develops precipitously, and without the blood test, the warning signs can be vague.

“A woman can go from feeling fine and being completely healthy and having normal kidney and liver function, and within 24 to 48 hours those organs can fail and she develops brain swelling and seizures,” Dr. Thadhani said. “That is the scary part of the disease.”