As concerns mount over people's exposure to the plasticizer bisphenol A in everyday products, it's also contaminating the air near manufacturing plants: U.S. companies emitted about 26 tons of the hormone-disrupting compound in 2013.
Although research is sparse, experts warn that airborne BPA could be a potentially dangerous route of exposure for some people. Of the 72 factories reporting BPA emissions, the largest sources are in Ohio, Indiana and Texas, according to the Environmental Protection Agency's Toxics Release Inventory.
No one has measured what people in nearby communities are exposed to. But the exposures are likely to be localized and smaller than other sources of BPA.
BPA breaks down quickly in the environment. But it also can attach to particles that infiltrate lungs, said Bruce Blumberg, a University of California, Irvine, biology professor.
"Inhalation of compounds is a big exposure route that most people do not usually consider for BPA," he said.
BPA, used to make polycarbonate plastic, food can linings and some paper receipts, is found in almost all people tested. Low doses can alter hormones, according to animal tests, and exposure has been linked to a wide range of health effects in people, including infertility, cardiovascular disease, obesity and cancer.
In the air
In the only study of its kind, Japanese researchers reported that BPA was ubiquitous in the atmosphere worldwide. They suspected the emissions came from the manufacturing and burning of plastics.
In the United States, chemical manufacturing accounted for 54 percent of the BPA air emissions, while metal manufacturing and metal fabricating accounted for 21 and 20 percent, respectively, according to the EPA database. In addition, U.S. companies in 2013 reported releasing 3,313 pounds of BPA to surface waters, the EPA database shows.
The amount of BPA emitted into the air has been dropping in recent years. Although the number of companies reporting BPA emissions has remained about the same over the past decade, in 2013 the total tons declined 41 percent from 2012 and almost 66 percent from 10 years ago.
Kathryn St. John, a spokesperson for the American Chemistry Council, which represents chemical manufacturers, said the data don't reflect what people in surrounding communities might be exposed to. Factors such as the proximity of people to the plants and whether the emissions are continuous or intermittent are important when determining people's exposures.
St. John added that there is "no evidence that inhalation exposures are of concern." Studies have not provided any information on what happens to BPA if inhaled, such as whether it is absorbed in the lungs and if absorbed, whether it is metabolized.
But Wade Welshons, an associate professor at the University of Missouri who studies endocrine-disrupting compounds, said airborne BPA could be absorbed through the lungs as well as the skin.
Both and inhalation and skin absorption "would deliver more BPA to the blood than an oral exposure," he said.
Blumberg and Welshons said since these routes would bypass metabolizing organs such as the intestines and liver, airborne exposures may be more dangerous than food exposures.
"The liver is a great organ for metabolizing substances, lungs are for absorbing, not for metabolizing," Welshons said.
No one has investigated the potential health effects of inhaling BPA. Regulatory agencies only consider oral doses when analyzing potential effects, Blumberg said.
Concern for infants
Several communities with the biggest BPA emitters are also home to large volumes of other toxics from industrial plants.
Deer Park, Texas, had 4,100 pounds of BPA and 2.8 million pounds of other air toxics in 2013, while Defiance, Ohio, had 6,600 pounds of BPA and 387,454 pounds of others, according to the industry reports filed with the EPA. Freeport, Texas, home to a Dow Chemical plant, had 905 pounds of reported BPA air emissions last year and an additional 1.74 million pounds of other toxics.
Compared with exposure from consumer products such as polycarbonate plastic and food cans, there has been little concern about airborne BPA. "But this lower concern level is based on relatively little data," said Laura Vandenberg, an assistant professor of environmental health at the University of Massachusetts Amherst who studies health effects of BPA. "This is something I would say is not discussed in-depth on our field but it should be."
There isn't a lot of research on what happens to BPA when it's released into the air. BPA degrades fairly quickly, but it also can attach to dust particles, Vandenberg said.
Researchers tested for BPA in the dust of homes, dorms and labs at and around Murray State University and the University at Albany in 2011. They estimated that, while diet is the still the major exposure route, people's BPA exposures through dust are about the same as the low concentrations that cause health problems in lab animals. It's not clear how the BPA got into the dust; it could have been from indoor sources.
Sudan Loganathan, who led the study while a student at Murray State University, said the estimated daily exposure for people through dust was low compared with food exposure. But, she added, "when you look at the average dust intake for adults and then infants, this is more of a concern for infants. They are on the floor, and there's more hand-to-mouth contact."
Blumberg said air quality monitoring should expand to test for BPA.
"There are a lot of people studying inhalation exposure with things like particulate pollution, ozone and other major components of exhaust, but not much at all when it comes to chemical exposure like BPA," Blumberg said. "That's a big open area right now."
Ohio, Indiana and Texas are home to the nation's top emitters of bisphenol A. In all, about 26 tons were released into the air in 2013, according to industry reports filed with the Environmental Protection Agency.
1. Sunoco Haverhill North Coke Co./Haverhill Chemicals
Franklin Furnace/Haverhill, Ohio
Petroleum coal products manufacturing/chemicals manufacturing
2013 BPA emissions: 13,500 pounds
Sunoco Haverhill North Coke Co. is now called SunCoke Energy and representatives said the report listing the company as the nation's top air emitter is incorrect. Spokesperson Lisa Ciota said the emissions are from nearby Haverhill Chemicals, which manufactures BPA. She said the facility, formerly owned by Sunoco, changed ownership in 2011 but their emissions were erroneously lumped in with Sunoco facilities in the 2013 report. The company is working with the EPA to fix the report. Haverhill Chemicals did not return a request for comment. Their website states that they have manufactured 100,000 tons of BPA.
2. Manitex Sabre Inc.
2013 BPA emissions: 10,429 pounds
Manitex Sabre did not return requests for comment. The company's website says it designs and manufactures liquid storage containers, called "frac tanks," which are commonly used to store liquids when oil and gas wells are pumped.
3. GM Defiance Casting Operations
2013 BPA emissions: 6,600 pounds
GM Defiance did not return requests for comment. The plant manufactures cylinder blocks and heads and crankshafts, according to its website.
4. Momentive Specialty Chemicals Inc.
Deer Park, Texas
Chemicals, plastics manufacturing
2013 BPA emissions: 4,100 pounds
Momentive Specialty Chemicals reduced its BPA emissions by 21 percent in 2013 compared with 2012, said John Kompa, vice president of investor relations and public affairs. Kompa didn't comment on how the company reduced emissions but said "regulatory bodies around the world have reviewed the science and have found BPA to be safe." The company also released 278 pounds of BPA at a plant in Alexandria, La., and 390 pounds at a plant in Bedford Park, Ill.
5. Arnette Polymers LLC
Plastics, resin manufacturing
2013 BPA emissions: 1,861 pounds
Arnette Polymers did not return requests for comment. The company supplies epoxies and polyurethanes to the plastics industry, according to its website.
6. Esco Corp.
2013 BPA emissions: 1,602 pounds
Lisa Calais, a spokesperson for Esco Corp., said their emissions are probably not as high as reported. Calais said they based their BPA emissions since 2000 on information from a resin supplier. But, she said, the supplier recently tested emissions and concluded that "we have been grossly overestimating our emissions of BPA and that our actual BPA emissions are likely insignificant or immeasurable."
7 and 8. Sabic Innovative Plastics US LLC.
Burkville, Ala., and Mount Vernon, Ind.
Chemicals, plastics, resin manufacturing
Released: 1,412 pounds (Burkville) and 1,350 pounds (Mount Vernon)
Michael Wheeler, a spokesperson for Sabic Innovative Plastics, said in an emailed response that the company has installed controls to limit BPA emissions, but did not go into specifics. He said the company is "subject to stringent state and federal environmental permits and safety regulations. Based upon available scientific research, we are confident that these emissions do not pose a risk to our employees or our communities."
9. Huntsman Advanced Materials Americas Inc.
Chemicals, lastics, resin manufacturing
2013 BPA emissions: 1,200 pounds
Huntsman Advanced Materials did not return requests for comment. It is a chemical company that specializes in epoxy, acrylic and polyurethane products for manufacturers, including aerospace, automotive, construction, electronics and sporting equipment, according to its website.
10. Dow Chemical Co.
2013 BPA emissions: 905 pounds
Dow Chemical did not return requests for comment. Its website calls the Freeport, Texas, site the largest "integrated chemical manufacturing complex in the Western Hemisphere." The site is adding a propylene plant nearby in response to increasing supplies of shale gas. The plant also accounted for 64 percent of all BPA releases into surface water in 2013.