Blueberries have joined green beans in this year’s Dirty Dozen list | CNN

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CNN
 — 

Blueberries, beloved by nutritionists for their anti-inflammatory properties, have joined fiber-rich green beans in this year’s Dirty Dozen of nonorganic produce with the most pesticides, according to the Environmental Working Group, a nonprofit environmental health organization.

In the 2023 Shopper’s Guide to Pesticides in Produce, researchers analyzed testing data on 46,569 samples of 46 fruits and vegetables conducted by the US Department of Agriculture. Each year, a rotating list of produce is tested by USDA staffers who wash, peel or scrub fruits and vegetables as consumers would before the food is examined for 251 different pesticides.

As in 2022, strawberries and spinach continued to hold the top two spots on the Dirty Dozen, followed by three greens — kale, collard and mustard. Listed next were peaches, pears, nectarines, apples, grapes, bell and hot peppers, and cherries. Blueberries and green beans were 11th and 12th on the list.

A total of 210 pesticides were found on the 12 foods, the report said. Kale, collard and mustard greens contained the largest number of different pesticides — 103 types — followed by hot and bell peppers at 101.

Dirty Dozen 2023

2023 Dirty Dozen (most to least contaminated)

  • Strawberries
  • Spinach
  • Kale, collard and mustard greens
  • Peaches
  • Pears
  • Nectarines
  • Apples
  • Grapes
  • Bell and hot peppers
  • Cherries
  • Blueberries
  • Green beans
  • “Some of the USDA’s tests show traces of pesticides long since banned by the Environmental Protection Agency. Much stricter federal regulation and oversight of these chemicals is needed,” the report said.

    “Pesticides are toxic by design,” said Jane Houlihan, former senior vice president of research for EWG. She was not involved in the report.

    “They are intended to harm living organisms, and this inherent toxicity has implications for children’s health, including potential risk for hormone dysfunction, cancer, and harm to the developing brain and nervous system,” said Houlihan, who is now research director for Healthy Babies, Bright Futures, an organization dedicated to reducing babies’ exposures to neurotoxic chemicals.

    There is good news, though. Concerned consumers can consider choosing conventionally grown vegetables and fruits from the EWG’s Clean 15, a list of crops that tested lowest in pesticides, the report said. Nearly 65% of the foods on the list had no detectable levels of pesticide.

    2023 Clean 15

    2023 Clean 15 (least to most contaminated)

  • Avocados
  • Sweet corn
  • Pineapple
  • Onions
  • Papaya
  • Frozen sweet peas
  • Asparagus
  • Honeydew melon
  • Kiwi
  • Cabbage
  • Mushrooms
  • Mangoes
  • Sweet potatoes
  • Watermelon
  • Carrots
  • Avocados topped 2023’s list of least contaminated produce again this year, followed by sweet corn in second place. Pineapple, onions and papaya, frozen sweet peas, asparagus, honeydew melon, kiwi, cabbage, mushrooms, mangoes, sweet potatoes, watermelon, and carrots made up the rest of the list.

    Being exposed to a variety of foods without pesticides is especially important during pregnancy and throughout childhood, experts say. Developing children need the combined nutrients but are also harder hit by contaminants such as pesticides.

    “Pesticide exposure during pregnancy may lead to an increased risk of birth defects, low birth weight, and fetal death,” the American Academy of Pediatrics noted. “Exposure in childhood has been linked to attention and learning problems, as well as cancer.”

    The AAP suggests parents and caregivers consult the shopper’s guide if they are concerned about their child’s exposure to pesticides.

    Houlihan, director of Healthy Babies, Bright Futures, agreed: “Every choice to reduce pesticides in the diet is a good choice for a child.”

    Nearly 90% of blueberry and green bean samples had concerning findings, the report said.

    In 2016, the last time green beans were inspected, samples contained 51 different pesticides, according to the report. The latest round of testing found 84 different pest killers, and 6% of samples tested positive for acephate, an insecticide banned from use in the vegetable in 2011 by the EPA.

    “One sample of non-organic green beans had acephate at a level 500 times greater than the limit set by the EPA,” said Alexis Temkin, a senior toxicologist at the EWG with expertise in toxic chemicals and pesticides.

    When last tested in 2014, blueberries contained over 50 different pesticides. Testing in 2020 and 2021 found 54 different pesticides — about the same amount. Two insecticides, phosmet and malathion, were found on nearly 10% of blueberry samples, though the levels decreased over the past decade.

    Acephate, phosmet and malathion are organophosphates, which interfere with the normal function of the nervous system, according to the US Centers for Disease Control and Prevention.

    A high dose of these chemicals can cause difficulty breathing, nausea, a lower heart rate, vomiting, weakness, paralysis and seizures, the CDC said. If exposed over an extended time to smaller amounts, people may “feel tired or weak, irritable, depressed, or forgetful.”

    Why would levels of some pesticides be higher today than in the past?

    “We do see drops in some pesticides since the early ’90s when the Food Quality Protection Act was put into place,” Temkin said. “But we’re also seeing increases of other pesticides that have been substituted in their place which may not be any safer. That’s why there’s a push towards overall reduction in pesticide use.”

    Chris Novak, president and CEO of CropLife America, an industry association, told CNN the report “willfully misrepresented” the USDA data.

    “Farmers use pesticides to control insects and fungal diseases that threaten the healthfulness and safety of fruits and vegetables,” Novak said via email. “Misinformation about pesticides and various growing methods breeds hesitancy and confusion, resulting in many consumers opting to skip fresh produce altogether.”

    The Institute of Food Technologists, an industry association, told CNN that emphasis should be placed on meeting the legal limits of pesticides established by significant scientific consensus.

    “We all agree that the best-case scenario of pesticide residues would be as close to zero as possible and there should be continued science-based efforts to further reduce residual pesticides,” said Bryan Hitchcock, IFT’s chief science and technology officer.

    Many fruits and veggies with higher levels of pesticides are critical to a balanced diet, so don’t give them up, experts say. Instead, avoid most pesticides by choosing to eat organic versions of the most contaminated crops. While organic foods are not more nutritious, the majority have little to no pesticide residue, Temkin said.

    “If a person switches to an organic diet, the levels of pesticides in their urine rapidly decrease,” Temkin told CNN. “We see it time and time again.”

    If organic isn’t available or too pricey, “I would definitely recommend peeling and washing thoroughly with water,” Temkin said. “Steer away from detergents or other advertised items. Rinsing with water will reduce pesticide levels.”

    Additional tips on washing produce, provided by the US Food and Drug Administration, include:

    • Handwashing with warm water and soap for 20 seconds before and after preparing fresh produce.
    • Rinsing produce before peeling, so dirt and bacteria aren’t transferred from the knife onto the fruit or vegetable.
    • Using a clean vegetable brush to scrub firm produce like apples and melons.
    • Drying the produce with a clean cloth or paper towel to further reduce bacteria that may be present.

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    Understanding how mosquitoes smell humans could save thousands of human lives | CNN



    CNN
     — 

    Of the more than 3,000 species of mosquitoes in the world, just a small number have evolved to specialize in sucking human blood.

    How human-biting mosquitoes track us down so effectively isn’t currently known, but it matters, since they don’t just make us itch. They also carry dangerous diseases such as Zika, dengue, West Nile virus and malaria that can be deadly.

    In fact, stopping these pesky insects in their tracks could save up to half a million lives lost to those diseases each year.

    “In each of those cases where a mosquito has evolved to bite humans — which has only happened two or three times — they become nasty disease vectors,” said Carolyn “Lindy” McBride, an assistant professor of ecology and evolutionary biology at the Princeton Neuroscience Institute in New Jersey.

    That’s why she wants to understand how they find and target humans.

    “Mosquitoes mostly choose what to bite based on odor,” said McBride, whose lab focuses on the Aedes aegypti mosquito species that evolved to bite humans specifically.

    Only female mosquitoes suck blood since they need it to produce their eggs. Knowing how a potentially disease-carrying female mosquito sniffs out a person, while ignoring other warm-blooded animals, is a key query.

    Once that’s better known, much more effective repellents — or bait to lure mosquitoes away from humans — could be made, saving lives, said Christopher Potter, associate professor of neuroscience at Johns Hopkins University’s Center for Sensory Biology.

    If scientists can control their sense of smell, “we can really control what these mosquitoes are doing,” said Potter, who studies another human-specific mosquito, Anopheles, which carries malaria.

    It’s not an easy question to answer, since any animal smell is made up of hundreds of chemical compounds mixed together in specific ratios.

    “The actual chemicals that are found in human odor are basically the same as the chemicals found in animal odor — it’s the ratios and the relative abundance of those compounds in human mixtures that’s unique,” said McBride, whose research focuses on those issues.

    Each time a hungry female mosquito flies by, it’s doing complex chemical math in its tiny brain, figuring out what’s a human, what’s dog and what’s a flower.

    “To investigate, we decided to record neural activity in the brain of females while exposing them to natural human and animal odor extracts,” wrote Zhilei Zhao, a graduate student in McBride’s lab, in a Twitter thread describing the lab’s work. It took four years to develop “the necessary genetic reagents, odor delivery systems, and analytical approaches,” Zhao wrote.

    (From left) Noah Rose, a postdoctoral researcher at Princeton, and Gilbert Bianquinche survey a tree hole near Kedougou, Senegal, for Aedes aegypti larvae. More than half of the world's population lives in areas where Aedes aegypti mosquitoes are present.

    McBride’s lab team created a library of the chemical composition of animal odors. “That data set doesn’t really exist — so we decided to go out and collect it ourselves,” said Jessica Zung, a graduate student in McBride’s lab.

    Zung has collected scent samples from about 40 different animals so far, including guinea pigs, rats, quail and more.

    Comparing some of those to the 16 human samples, something jumped out. Decanal, a simple, common compound, is particularly abundant in human skin, Zung said.

    Ubiquitous in the natural world, in humans, decanal comes from another, more complex compound. Zung dug into the archives to find research from the 1970s (much of it originally done to find an acne cure) that detailed how when one component of our skin’s natural oils, sapienic acid, breaks down, decanal is left over. This acid (as indicated by its name) is only found in human beings. It’s what likely leads to the high levels of decanal that help the mosquitoes smell their way to us, but more studies need to be done.

    Understanding what the mosquitoes are sniffing out is only part of the story; knowing how they do it is also important. To see exactly how mosquitoes use this sense, scientists bred genetically modified Aedes aegypti mosquitoes “so that we could cut open their little tiny heads and put them under a fancy microscope and actually watch neurons firing when they’re exposed to human and animal odors,” McBride said.

    The research team already knew that mosquitoes have about 60 different types of neurons that sense odors, so when they looked in the insects’ brains, they thought they might see a lot of activity. But it was surprisingly quiet, meaning that the signal was perhaps quite simple, down to just a couple types of neurons.

    “One type of neuron responded really strongly to both humans and animals. Another type of neuron responded to both — but it responded much more strongly to humans than animals,” McBride said of that work. So it may be as simple as that mosquito’s brain comparing just two types of neurons.

    This kind of research has only been possible since the technology to study mosquito brains in detail became available, which only happened recently. “It’s been traditionally very hard to study this at the level we’re doing it now,” Potter said.

    Incredibly, mosquitoes that target humans have evolved to be able to do this in just the last 5,000 years, so it’s a “really amazing example of rapid evolution,” McBride said.

    The Aedes aegypti, aka “yellow fever mosquito” also carries dengue, Zika and chikungunya. The critter originated in Africa and likely made its way to its current range in the southern United States and Central and South America on slave ships during the 1600s, according to McBride.

    These diseases combined kill and sicken thousands of people a year, which is why mosquitoes have been called “the world’s deadliest animal” by the US Centers for Disease Control and Prevention. McBride and Potter both hope their work could be used by others working on repellents and attractants to prevent disease.

    As far as insider knowledge on how to keep from being bitten in your own backyard, McBride said she uses a fan.

    “Have it blow air over where you’re sitting outside or over the barbecue or under the table where they’re biting your feet.” It’s not that you’re blowing the scent around to knock the mosquitoes off track, she said.

    It’s simply because these deadly creatures, McBride said, “are not great fliers.”



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