Urban populations in Southern Californian are facing chronic exposure to toxic airborne "plasticizer" compounds — two of which have already been banned from children's products, a new study has found. Plasticizers are commonly used chemicals that serve the purpose of making materials more flexible, appearing in a wide range of products from food containers to shower curtains to gardening equipment to textiles, the authors noted. Despite regulatory efforts to minimize public exposure to the plasticizers most notorious for causing cancer, birth defects and reproductive harm, the presence of some compounds has persisted, according to the study, published in Environmental Research. “The levels of these compounds are through the roof,” said corresponding author David Volz, an environmental sciences professor at University of California, Riverside, in a statement. While previous research efforts in the Golden State have monitored the presence of specific types of plasticizers called "ortho-phthalates" — some of which were phased out of production due to health and environmental concerns — the scientists were interested in examining the presence of their replacements, known as "non-ortho-phthalates." But ultimately, they determined both types of plasticizers have persisted in the air throughout Southern California. To draw their conclusions, the researchers tracked two groups of UC Riverside undergraduate students, who wore silicone wristbands designed to collect airborne chemical exposure data. Each group commuted to the campus from different parts of Southern California. Members of the first group sported their wristbands for five days in 2019, while those in the second group wore two wristbands for five days each in 2020. All participants kept the bands on continuously as they went about their normal daily activities. At the end of each collection period, the researchers said they chopped the silicone bracelets into pieces and analyzed the chemicals they contained. For every gram of chopped-up wristband, the scientists found between 100,000 and 1 million nanograms of three types of phthalates: DiNP, DEHP and DEHT. A 2007 California law prohibited the manufacture, processing and distribution of children's products containing DEHP or DiNP in concentrations exceeding 0.1 percent as of January 2009. The federal government took similar action on these compounds through the Consumer Product Safety Improvement Act of 2008. DEHP and DiNP appear on California's Proposition 65 list, which publicizes chemicals known to cause cancer and reproductive issues. While DEHT was introduced as an alternative to these chemicals, the authors said its impacts on human health remain unclear. Regardless of DEHT's effects, the scientists stressed its promulgation has not done much to decrease the public's exposure to DiNP or DEHP. Concentrations of all three chemicals, they noted, were similar to those identified in unrelated studies on the East Coast. “No matter who you are, or where you are, your daily level of exposure to these plasticizer chemicals is high and persistent,” Volz said. “They are ubiquitous.”