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Environmental groups sue FDA over agency’s refusal to restrict phthalates

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Tuesday, January 7, 2025

A coalition of environmental groups has sued the US Food and Drug Administration (FDA) over the use of highly toxic phthalates in plastic food packaging because the chemicals have been found to leach at alarming rates and present a serious health risk, especially for developing children.The suit is the latest salvo in an ongoing eight-year battle in which advocates have pressured the FDA to ban the chemicals’ use in food packaging, but the agency has sided with industry that opposes the calls. Since 2016, the FDA has either illegally ignored petitions or rejected demands to revoke a 40-year-old authorization for the chemicals that is based on long-outdated science.The health groups in a statement called the FDA’s refusal to restrict the chemicals “unconscionable”.“The FDA is knowingly putting millions of people in the US at risk of life-altering health problems by continuing to greenlight uses of phthalates that contaminate our food,” said Katherine O’Brien, an attorney with Earthjustice, one of the suit’s lead plaintiffs. “FDA’s decision defies decades of science and the agency’s core purpose of keeping the food supply safe.”The FDA did not immediately respond to a request for comment.Phthalates are a class of nearly 30 chemicals used as plasticizers in plastic containers, kitchen utensils and food preparation materials, among other uses. Researchers have found them in most food samples tested in recent years, and very low levels of exposure are linked to birth defects and pre-term birth. They are thought to cause developmental harms for fetuses and children, especially the reproductive system and brain – kids who have been exposed risk reduced IQ, and boys risk genital defects and infertility.Phthalates are also particularly dangerous because they have been found to mimic the human body’s hormones.The European Union has banned or restricted some phthalate compounds in food contact, but few regulations exist in the US. However, three types of phthalates have been banned for use in kids’ toys in the US because children were ingesting the chemicals.The lack of regulations is due in part to industry pressure on the FDA, public health advocates allege. The American Chemistry Council, a trade group that represents chemical makers, has attacked research on phthalates’ ubiquity and dangers, and argues that not all phthalates present a risk. Claims that they do create “unnecessary public alarm about our nation’s food safety”, the council wrote in a statement.The FDA has largely agreed with that view. The coalition that filed the lawsuit first petitioned the FDA to revoke authorizations for phthalate use in food contact in 2016. It highlighted decades of scientific evidence linking the chemicals to health risks, especially for kids.The FDA did not respond to the petition for five years, violating the law, which requires a response within six months. The groups in 2021 sued the FDA, forcing it to respond. In 2022, the agency denied the petition, arguing that industry had already abandoned food contact use for most phthalates.skip past newsletter promotionafter newsletter promotionThe groups filed an appeal to reconsider, but the FDA upheld its decision in October 2024, allowing phthalates to continue to be used without restrictions. The agency wrote that it “found that available information does not support grouping all 28 phthalate chemicals into a single class assessment”.Public health advocates say the agency is echoing industry talking points.“The FDA has decided to ignore years of research and failed to take action to protect our health from these chemicals widely known to cause harm, allowing business as usual for companies who profit from their use,” said Maria Doa, an attorney with the Environmental Defense Fund, a co-litigant.The new suit asks a judge to order a ban on the chemical class.In the meantime, people can protect themselves by avoiding food in plastic containers, using glass containers in the kitchen, avoiding plastic kitchenware and eating fewer processed foods.

Agency has either ignored petitions or ruled against taking action against chemical that presents serious health risksA coalition of environmental groups has sued the US Food and Drug Administration (FDA) over the use of highly toxic phthalates in plastic food packaging because the chemicals have been found to leach at alarming rates and present a serious health risk, especially for developing children.The suit is the latest salvo in an ongoing eight-year battle in which advocates have pressured the FDA to ban the chemicals’ use in food packaging, but the agency has sided with industry that opposes the calls. Since 2016, the FDA has either illegally ignored petitions or rejected demands to revoke a 40-year-old authorization for the chemicals that is based on long-outdated science. Continue reading...

A coalition of environmental groups has sued the US Food and Drug Administration (FDA) over the use of highly toxic phthalates in plastic food packaging because the chemicals have been found to leach at alarming rates and present a serious health risk, especially for developing children.

The suit is the latest salvo in an ongoing eight-year battle in which advocates have pressured the FDA to ban the chemicals’ use in food packaging, but the agency has sided with industry that opposes the calls. Since 2016, the FDA has either illegally ignored petitions or rejected demands to revoke a 40-year-old authorization for the chemicals that is based on long-outdated science.

The health groups in a statement called the FDA’s refusal to restrict the chemicals “unconscionable”.

“The FDA is knowingly putting millions of people in the US at risk of life-altering health problems by continuing to greenlight uses of phthalates that contaminate our food,” said Katherine O’Brien, an attorney with Earthjustice, one of the suit’s lead plaintiffs. “FDA’s decision defies decades of science and the agency’s core purpose of keeping the food supply safe.”

The FDA did not immediately respond to a request for comment.

Phthalates are a class of nearly 30 chemicals used as plasticizers in plastic containers, kitchen utensils and food preparation materials, among other uses. Researchers have found them in most food samples tested in recent years, and very low levels of exposure are linked to birth defects and pre-term birth. They are thought to cause developmental harms for fetuses and children, especially the reproductive system and brain – kids who have been exposed risk reduced IQ, and boys risk genital defects and infertility.

Phthalates are also particularly dangerous because they have been found to mimic the human body’s hormones.

The European Union has banned or restricted some phthalate compounds in food contact, but few regulations exist in the US. However, three types of phthalates have been banned for use in kids’ toys in the US because children were ingesting the chemicals.

The lack of regulations is due in part to industry pressure on the FDA, public health advocates allege. The American Chemistry Council, a trade group that represents chemical makers, has attacked research on phthalates’ ubiquity and dangers, and argues that not all phthalates present a risk. Claims that they do create “unnecessary public alarm about our nation’s food safety”, the council wrote in a statement.

The FDA has largely agreed with that view. The coalition that filed the lawsuit first petitioned the FDA to revoke authorizations for phthalate use in food contact in 2016. It highlighted decades of scientific evidence linking the chemicals to health risks, especially for kids.

The FDA did not respond to the petition for five years, violating the law, which requires a response within six months. The groups in 2021 sued the FDA, forcing it to respond. In 2022, the agency denied the petition, arguing that industry had already abandoned food contact use for most phthalates.

skip past newsletter promotion

after newsletter promotion

The groups filed an appeal to reconsider, but the FDA upheld its decision in October 2024, allowing phthalates to continue to be used without restrictions. The agency wrote that it “found that available information does not support grouping all 28 phthalate chemicals into a single class assessment”.

Public health advocates say the agency is echoing industry talking points.

“The FDA has decided to ignore years of research and failed to take action to protect our health from these chemicals widely known to cause harm, allowing business as usual for companies who profit from their use,” said Maria Doa, an attorney with the Environmental Defense Fund, a co-litigant.

The new suit asks a judge to order a ban on the chemical class.

In the meantime, people can protect themselves by avoiding food in plastic containers, using glass containers in the kitchen, avoiding plastic kitchenware and eating fewer processed foods.

Read the full story here.
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Ancient Romans Breathed in Enough Lead to Lower Their IQs, Study Finds. Did That Toxin Contribute to the Empire’s Fall?

Using Arctic ice core samples, researchers estimate silver mining and smelting released enough lead during the Pax Romana to cause a 2.5- to 3-point drop in IQ

At the same time as the Romans were building the Colosseum, they were also breathing in high amounts of toxic lead from silver mining and smelting operations. Hussain Didi via Wikimedia Commons under CC BY-SA 3.0 Did lead poisoning contribute to the fall of the Roman Empire? It’s a question historians have long debated, since the Romans sweetened their wine with lead acetate and sipped tap water that flowed through lead pipes. Now, new research suggests the Romans were also breathing in large amounts of lead from silver mining and smelting operations. The toxic metal polluting the air likely got into children’s blood, leading to “widespread cognitive decline,” researchers write in a new paper published Monday in the journal Proceedings of the National Academy of Sciences. Lead in the air might have caused an estimated 2.5- to 3-point drop in IQs throughout the Roman Empire, per the research. The new paper doesn’t solve the mystery of whether lead poisoning played a role in Rome’s downfall. But it does add new evidence to the debate. “I’m quite convinced lead was one of the factors that contributed to the decline of the Roman Empire, but it was only one factor,” says Bruce Lanphear, a health scientist at Simon Fraser University in Canada who was not involved with the study, to NBC News’ Evan Bush. “It’s never just one thing.” Researchers say their findings also represent the first documented example of human-caused industrial pollution in history. To estimate lead pollution levels in ancient Rome, researchers turned to ice core samples taken from Greenland and Russia. For decades, scientists have been using large drills to penetrate Arctic ice sheets and extract columns of ice up to 11,000 feet long. These columns function like frigid time machines: As snowflakes fall, they capture chemicals and particles from the air. When the snow touches down in the Arctic, it compresses and solidifies into thin layers of ice—with those chemicals and particles still trapped inside. By studying these layers, scientists can effectively peer back in time. “You built up this layer cake year after year of environmental history,” study co-author Joe McConnell, a climate and environmental scientist at the nonprofit Desert Research Institute in Nevada, tells NBC News. The team looked at layers of Arctic ice that corresponded to the period between 500 B.C.E and 600 C.E. They saw an increase in lead pollution around the year 15 B.C.E., which lines up with the early years of the Roman Empire. Lead levels remained high until 180 C.E., which marks the end of a period of relative peace known as the Pax Romana. During the roughly 200-year stretch of the Pax Romana, the Romans were extracting and smelting a lot of silver to make coins. These processes are known to emit large amounts of lead into the atmosphere. “If you produce an ounce of silver, you’d have produced something like 10,000 ounces of lead,” McConnell tells the New York Times’ Katherine Kornei. Using the lead levels they found in the ice samples, the researchers were able to work backward and estimate how much lead the Romans must have been spewing into the air. Atmospheric modeling suggests between 3,300 and 4,600 tons of lead were released each year during the Pax Romana, per the New York Times. The scientists estimate that lead pollution was the worst in areas next to mining and smelting operations, reaching concentrations of at least 150 nanograms per cubic meter of air. The toxins would have also spread across Europe—they estimate average concentrations of lead air pollution were greater than 1 nanogram per cubic meter over the continent. Next, they used modern data to estimate how much lead would have built up in the blood of ancient Roman children. They were then able to extrapolate how these accumulations might have affected their IQ. The researchers focused on children in particular, because kids are especially vulnerable to the health consequences of lead exposure. Today, global health experts agree that no amount of lead is safe for kids. The heavy metal can build up in the body and cause health problems. In addition to lowering IQ, lead accumulation in children can lead to slowed growth, anemia, hearing problems, hyperactivity and behavior and learning problems. “We have actual data on IQ scores in kids with different blood-lead concentrations,” Deborah Cory-Slechta, a neurotoxicologist at the University of Rochester Medical Center who was not involved with the paper, tells the New York Times. Roman children likely had an extra 2.4 micrograms of lead per deciliter of blood from the empire’s air pollution. That correlates to a drop in IQ of between 2.5 and 3 points. Factoring in background lead exposure, their blood levels of lead may have been as high as 3.5 micrograms per deciliter, the researchers estimate. And that doesn’t take into account other sources of lead exposure, so the team’s findings are probably an underestimate, reports NBC News. For reference, American children had around 15 micrograms of lead per deciliter of blood during the 1970s, before lead paint and leaded gasoline were banned. Those levels likely resulted in a 9-point drop in IQ, per the New York Times. “A 2.5- to 3-point reduction in IQ may not sound like much but it was across the entire population and would have persisted for the nearly 180 years of the Pax Romana,” McConnell tells the Guardian’s Ian Sample. “I leave it to epidemiologists, ancient historians and archaeologists to determine if the levels of background atmospheric lead pollution and health impacts we have identified … were sufficient to change history.” But even factoring in these new findings, some experts remain skeptical that lead poisoning caused the Roman civilization to collapse around 476 C.E. “While the magnitude of exposure and the correlated blood lead levels were enough to negatively affect the cognitive function of that population, this is still a far cry from causing the downfall of the Roman Empire,” says Amy L. Pyle-Eilola, a pathologist at the Ohio State University who was not involved with the research, to New Scientist’s Christa Lesté-Lasserre. Caleb Finch, a neurobiologist at the University of Southern California who was not involved with the research, remains similarly unconvinced. “The conclusion of ‘widespread cognitive decline’ from an estimated three-IQ point decrease does not match the huge productivity of the Roman Empire, when lead production was maximal,” he tells Science’s Taylor Mitchell Brown. Get the latest stories in your inbox every weekday.

Exxon Mobil sues California Atty. Gen. Rob Bonta over plastic recycling claims

Exxon lawsuit accuses California's attorney general, the Sierra Club and others of defaming the oil giant with negative comments about plastic recycling.

Oil giant Exxon Mobil has filed a defamation lawsuit against California Atty. Gen. Rob Bonta, claiming Bonta falsely accused the company of deceiving the public about the potential for plastic recycling.The suit, filed Monday in federal court in the Eastern District of Texas, amounts to a counterpunch against a suit Bonta filed against Exxon Mobil last September accusing the company of greatly exaggerating the extent to which plastics can be recycled by portraying them as universally recyclable.Exxon claims that accusations by Bonta and environmental groups have damaged its reputation with customers.“With apparently no appreciation for the irony of their claim, Mr. Bonta and his cohorts are now engaging in reverse greenwashing,” according to the complaint, which also names environmental groups including the Sierra Club and the Surfrider Foundation. “While posing under the banner of environmentalism, they do damage to genuine recycling programs and to meaningful innovation,” the lawsuit says.The legal battle underscores a widening rift between California and oil companies. Plastics are a product of the petroleum industry, created by processing chemicals found in hydrocarbons.Bonta‘s suit against Exxon goes beyond issues of consumer deception to address plastic manufacturing itself. Plastic waste is increasingly recognized as a serious global pollution problem. The Bonta suit seeks financial penalties “for the harm inflicted by plastics pollution upon California’s communities and the environment.”Bonta alleged the company “falsely promoted all plastic as recyclable” while the recycling rate of plastics in the U.S. is below 10%. Exxon has disputed those claims. The battle against Big Oil has become a hallmark of the administration of Gov. Gavin Newsom. He’s accused oil companies of price gouging, although state efforts to prove it have thus far born no fruit. Newsom coaxed the state Legislature in two special sessions to create a price gouging investigation unit and to require oil refineries to keep extra stocks of gasoline on hand to prevent price spikes when refineries shut down for maintenance.The governor is seeking to keep gasoline prices down as the state increasingly squeezes its oil refineries with its electric vehicle mandate. In 2020, Newsom ruled that automakers increase sales of new zero-emission vehicles over time until 2035, when state policy will ban sale of new traditional gasoline and diesel fueled cars and light trucks.At the same time, California is increasing financial penalties on the state’s oil refineries through its Low Carbon Fuel Standards program.The Big Oil battle raises questions about future gasoline supply and prices at the pump if more oil companies abandon the state. In October, Phillips 66 announced plans to shut down its Los Angeles-area refinery, although it will retain its service stations here. The oil company said market conditions, not recent state policies, drove the decision.

Opinion: What antiabortion activists want next

The Supreme Court said states should decide access to abortion, but activists are mounting lawsuits and lobbying Washington for what could amount to a national ban.

The state of Texas filed a major lawsuit on Dec. 12 against a New York doctor who mailed abortion pills to a Collin County, Texas, woman, arguing that the doctor was practicing medicine without a Texas license and violating the state’s abortion ban. The suit raises messy legal questions about whether one state can haul a doctor abiding by the law in another state into its courts, or enforce a judgment if it wins. More than that, however, the suit is a window into the next battlefield over abortion rights — and how abortion pills and telemedicine are reshaping the politics of abortion in America.The antiabortion movement’s endgame is establishing fetal personhood — the idea that life and constitutional rights begin at the moment sperm fertilizes an egg. Fetal personhood was referenced in the 2024 GOP platform and embraced in a strategy endorsed by most leading antiabortion groups. It has been a focal point of the movement’s efforts for 50 years.But with blue states and many red states reaffirming a right to abortion, fetal personhood doesn’t seem like it’s going to come to pass anytime soon. In the meantime, abortion opponents have set their sights on shutting down access to abortion pills — mifepristone and misoprostol. The Supreme Court rebuffed one Texas lawsuit targeting mifepristone in June (on the basis of standing), but as the new case indicates, that hasn’t discouraged the antiabortion movement. Here’s why: Medication abortion, also called chemical abortion, has made it difficult to enforce abortion bans in the states where they exist — indeed, even with Roe vs. Wade reversed, studies show an increase in the number of abortions performed annually in the U.S. Abortion pills also make it harder to frighten doctors and harder to stigmatize the termination of pregnancy.When all abortions were surgical, the procedure had to take place in bricks-and-mortar facilities. The clinics became targets for protest and sometimes violence and vandalism. Abortion pills, however, can be prescribed remotely, through a telehealth consultation, and they are taken at home very early in a pregnancy. Pills make abortion more private, distancing patients from clinic protests, and their effects may resemble miscarriage, which already occurs in up to 20% of known pregnancies — so much so that physicians have no reliable way of telling the symptoms apart. Along with backlash against the reversal of Roe, the nature of medication abortion seems to be reshaping how Americans think about terminating a pregnancy: The number of those who see abortion as a moral decision has increased in recent years.The Texas lawsuit is part of a much broader antiabortion strategy that will unfold in the new year. Besides targeting telemedicine and pills, antiabortion groups plan to pursue anyone who aids or abets abortion — for example, internet service providers that allow websites to provide information about abortion pills and where to get them. Other proposals copy a Louisiana law that designates safe and effective drugs used in abortion as “controlled substances.” In addition to these maneuvers, look for abortion opponents to lobby the Trump administration to reinterpret the Comstock Act, a 19th century obscenity law, to make it illegal to send anything used in abortions by mail. That could create the equivalent of a nationwide ban, which Congress so far won’t legislate and voters don’t want.And there are other steps the Trump administration could take that would dramatically change abortion access. In 2023, the Food and Drug Administration made changes to the restrictions governing mifepristone and telemedicine abortion appointments. Ever since, antiabortion groups have developed a grab-bag of arguments against the FDA’s rules. They argue that the consensus of peer-reviewed studies is wrong and that mifepristone is extremely dangerous. They also have argued that mifepristone and fetal “remains” are an environmental hazard polluting groundwater. Robert F. Kennedy Jr., who would have oversight of the FDA if he is confirmed as Trump’s pick to be secretary of the Department of Health and Human Services, said he was pro-choice on the campaign trail, but he also has signaled openness to the antiabortion movement. Claims about drug safety and environmental hazards might resonate with Kennedy, who is an opponent of Big Pharma and once worked in environmental law.The Supreme Court decision overturning Roe has done nothing to end abortion battles; instead, it has given them new life. Fights over telemedicine consultations, mail-order access to abortion pills and FDA safety rules could make abortion bans far more effective, reshape the procedure in states that protect abortion rights and expand the power of one state to dictate policy in another.Most important: If abortion opponents succeed in making abortion pills inaccessible, the stigma surrounding abortion may well increase, and access to the procedure decrease. That’s why antiabortion groups have been relentless in their pursuit of pills. Nothing less than Americans’ view of abortion itself is on the line.Mary Ziegler is a law professor at UC Davis. Her latest book, “Personhood: The New Civil War over Reproduction,” is scheduled for publication in April.

Your prescription drugs could be leaching toxic chemicals into wastewater

Researchers found that chemicals from pharmaceuticals that include PFAS are entering into wastewater — which can end up in drinking water during times of drought.

The widespread use of pharmaceuticals in America is introducing even more toxic “forever chemicals” into the environment through wastewater, according to a study released Monday, and large municipal wastewater treatment plants are not capable of fully filtering them out.The plants’ inability to remove compounds known as organofluorines from wastewater before it enters drinking water supplies becomes even more pronounced during droughts and could affect up to 23 million people, scientists wrote in an article published Monday in Proceedings of the National Academy of Sciences. Most of the compounds came from commonly prescribed medications including antidepressants and statins, the researchers found.They found that the organofluorines — a group that includes per- and polyfluoroalkyl substances, or PFAS — were found in wastewater in eight large municipal treatment plants. The wastewater continued to contain high concentration of organofluorines and other compounds that meet the definition of PFAS even after treatment.The researchers found up to three-quarters of the extractable compounds were from 12 commonly prescribed fluorinated medicines, including antidepressants, statins and medications used to treat Type 2 diabetes and HIV. The facilities removed less than 25 percent of the compounds during treatment, the researchers found.Follow Climate & environmentBridger Ruyle, the study’s lead author, said that the fluorinated chemicals from pharmaceuticals aren’t fully metabolized and leave the body with waste. They then enter the wastewater stream and the environment.“That means that downstream aquatic organisms and potentially people drinking drinking water may also now be exposed to these pharmaceuticals,” Ruyle said.The American Chemical Society and the Product Quality Research Institute did not immediately respond to requests for comment.PFAS, also known as forever chemicals, are a class of thousands of carbon-fluorine bonded compounds manufactured to make products and coatings that repel grease, water, oil and heat. The persistent chemicals are found in hundreds of household items including nonstick cookware, menstrual products, dental floss and medicines.In the spring, the Environmental Protection Agency finalized the nation’s first drinking water standard for PFAS, limiting six specific PFAS chemicals from a class of thousands. The agency acted after mounting evidence suggested those chemicals in water can pose a health risk to people at even the smallest detectable levels of exposure.Wastewater collected from homes, industrial sites and businesses is typically transported to wastewater treatment plants. There, the wastewater is filtered, disinfected and discharged into streams and rivers. Some communities — particularly in times of drought — draw on water that includes the discharge for drinking water.But drought only exacerbates the amount of organofluorines found in treated wastewater that is used for drinking, the researchers found. This is because natural water supplies are diminished and do not dilute the treated wastewater before it enters the drinking water supply.Ruyle said the problem could become more pronounced as water becomes scarcer and populations grow, making it more difficult for natural water systems to dilute waste and communities more reliant on using treated wastewater for drinking.In the wastewater he tested, Ruyle said, regulated PFAS only made up about 8 percent of the PFAS found. The rest of the fluorinated compounds and PFAS present in the wastewater are not regulated by the EPA, he said. Some included precursor chemicals that can chemically transform into the regulated PFAS once in the environment, he said.Per- and polyfluoroalkyl substances have been linked to several kinds of cancer, infertility, high cholesterol, low birth weights, and negative effects on the liver, thyroid and immune system.The National Association of Clean Water Agencies, which represents wastewater treatment plants, said that in drought-stricken areas, the connection is closer between drinking water sources and wastewater.“Anything we eat, drink or put into our bodies … whatever types of compounds, chemicals, pollutants, whatever words you want to use, that’s all going to make its way to a wastewater treatment plant,” said Adam Krantz, the association’s chief executive. “It’s all one water. The water cycle remains the water cycle, and there’s only as much water as we currently have on Earth.”Krantz said water utilities and wastewater facilities are responsible for following the Safe Drinking Water and Clean Water acts.He said water utilities and wastewater management systems should not bear the brunt of fixing PFAS-related problems; instead, it should be up to manufacturers, which are “the primary source and the ones making the money off of these products to begin with.”“The major way to avoid all of those concerns is to take the bad stuff out from the source and to make the polluter pay for that, because these things are coming into the water and wastewater treatment plants from manufacturers,” Krantz said.Water and waste utilities around the country are working to tackle chemicals in drinking water, said Ralph Exton, executive director of the Water Environment Federation, an association of water and wastewater professionals.“These utilities are largely involuntary receivers of contaminants of emerging concern … like PFAS and pharmaceuticals,” Exton said. “For example, pharmaceuticals tend to enter the waste stream through human excrement and the improper disposal of medications.”The group has urged Congress to provide more funding for research and innovation so that the cost of mitigation does not fall on utilities and their customers.Carrie McDonough, an assistant professor of chemistry at Carnegie Mellon University, said the study highlights the prevalence and persistence of fluorinated pharmaceuticals. She said we need to consider using these chemicals only when they are essential, because dilution does not reduce them to low levels.“Traditional wastewater treatment techniques that work pretty well for a lot of other wastewater-associated contaminants aren’t going to break apart a carbon-fluorine bond,” she said.While very little is known about the long-term exposures of pharmaceutical waste on people living downstream or how such waste definitively affects drinking water, Ruyle said there needs to be more research done to consider the environmental persistent secondary exposures to pharmaceuticals.“I think what this study really emphasizes is how prevalent these chemicals are in major PFAS sources and highlights the need for us to better understand what exposures and potential risks are to these classes of chemicals,” Ruyle said.

Study: Sulfur helps gold reach Earth’s surface

Scientists have long suspected that sulfur, which forms strong chemical bonds with gold, allows it to be transported up to the surface.

Gold deposits are often found in places with intense volcanic activity, and scientists have long known that the sparkly substance gets there with the help of magma, the molten rock that fuels volcanoes. But gold is a dense metal that originates in Earth’s mantle, far beneath the surface. So how does it manage to rise up to form gold deposits on the surface?That question has long vexed scientists, but a recently published analysis in PNAS offers an explanation. The study, conducted by an international team of researchers, developed a thermodynamic model that predicts why gold gushes upward with volcanic activity.The action occurs in deep-sea subduction zones where tectonic plates collide. As one plate slips beneath its neighbor, volcanic activity can move magma from Earth’s mantle — the geologic layer that sits between Earth’s hot core and its crust — upward.Usually, gold is locked within Earth’s mantle. But scientists have long suspected that sulfur, which forms strong chemical bonds with gold, allows it to be transported in magma up to the surface.The new thermodynamic model quantitatively predicts what happens in these subduction zones. The researchers discovered that sulfur in the mantle can combine with gold, creating a stable complex that can transport large amounts of gold upward from Earth’s mantle to its crust through magma.The complex, known as a gold-trisulfur complex, “acts as an extremely effective agent to transport and concentrate” gold, the researchers write, extracting up to 100 times more gold from the mantle than areas without the fluid.“The same types of processes that result in volcanic eruptions are processes that form gold deposits,” Adam Simon, a University of Michigan professor of Earth and environmental sciences and a co-author of the study, said in a news release. “This thermodynamic model that we’ve now published is the first to reveal the presence of the gold-trisulfur complex that we previously did not know existed at these conditions,” Simon said.It’s the “most plausible explanation” for high gold concentrations in places like the gold-rich Ring of Fire region of the Pacific Ocean, which has abundant active volcanoes, he adds.

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