Discussion: (0 comments)
There are no comments available.
View related content: Health Care
If you’re having trouble getting pregnant, plastics may be the culprit—at least that’s what a credulous reader might conclude based on recent news reports and a slew of website stories with headlines like: “New studies link BPA and phthalates to miscarriage and infertility.”
But as is often the case when journalists report on complex science issues, the headlines do not align with the facts. A careful reading of the actual studies and the established research history suggest that these substances do not pose any unusual dangers, despite bumbling efforts by the media and even some scientists to spin the findings to scare up publicity. But the misreporting of conflicting data is not just a case of bad journalism. The consequences are far more pernicious, as scare stories end up infecting the public discussion and the result is often bad legislation.
The source of the inflammatory news reports was a press release designed to hype last month’s annual meeting of the American Society for Reproductive Medicine (ASRM). The release publicized two obscure studies on the fertility impacts of exposure to bisphenol A (BPA) and a class of compounds known as phthalates. As often happens when so-called “endocrine disruption” chemicals are being discussed, the media went into scare overdrive. The flurry of misleading articles comes as the government is poised to make some critical decisions about how to regulate a ubiquitous plastic additive.
Let’s focus on one of the two reports that the media latched onto, the potential impact of the two chemicals on male and female fecundity. The as yet unvetted study followed 501 couples trying to become pregnant. The researchers documented the couples’ sex lives and provided urine samples to measure levels of the two chemicals in the crosshairs of activists.
Thin case claiming BPA, phthalates pose serious health risks
BPA is an ingredient used in bottles, can liners and dental fillings to make them clear and more durable. As I’ve discussed before at Forbes and Huffington Post, the chemical has been alleged to cause everything from cancer to reproductive problems. But the science is gradually moving in the opposite direction. Even as some reporters continue to flog the BPA-is-dangerous horse, independent government-funded studies investigating the ‘black box’ theory that BPA disrupts our endocrine system suggest that it is unlikely to have serious impacts on human health because the liver neutralizes the microscopic trace levels absorbed by humans.
Phthalates and other plasticizers are chemicals that improve the flexibility and strength of plastics. They are commonly found in medical devices, flooring, tubing, roofing, adhesives and even some cosmetics. While rodents exposed to phthalates (often through injections) have, in some cases, shown evidence of reproductive problems, these potentially serious effects have not consistently shown up in state-of-the-art human studies.
As in the case of BPA, phthalates have been accused of being so-called “endocrine disruptors.” Allen Godwin, a chemist, inventor with more than two dozen plasticizer patents and now a lecturer at Texas A&M University, estimates there are thousands of chemicals available for use in plastics, and some unknown number of them can interact with our endocrine system—as do many natural substances, like many nuts and soybeans and common synthetic products, like birth control pills. The question for scientists and regulators: Are there types of phthalates that impact the female reproductive system and if so could they cause serious disruption?
That’s the debate now raging among reproductive scientists who embrace the precautionary principle, which urges restrictions based upon concerns about potential harm even if there is no strong evidence of documentable dangers. Most toxicologists and the majority of mainstream scientists from other disciplines believe the links between certain chemicals and endocrine related health problems are often overblown. They urge that we rely on the totality of available evidence rather than be unduly swayed by the results of one-off studies that seem to point to a hazard but often fail to be replicated.
The ASRM meeting brought together endocrine disruptor theory true believers. According to the news release on the fertility study, men with high urine concentrations of phthalates experienced a 20% decline in fecundity and took longer to get their partners pregnant than men with lower concentrations.
What does that mean? Do humans face a serious health threat from these chemicals found in plastics and many other everyday products? The short answer is ‘no’.
Based on the brief summary of the still unreleased study, no links were found between BPA in the urine and reproductive impacts on men or women. None. In fact, phthalates actually boosted female fertility— a stunning finding that didn’t find its way into most news reports. That means that phthalates show no harmful estrogenic impacts—there is no evidence from this study that it’s an endocrine disruptor.
That didn’t stop ASRM leaders from spinning the data. “These studies … show that these chemicals are a cause for concern to all of us,” said Linda Giudice, an obstetrician, gynecologist and reproductive endocrinologist at University of California San Francisco Medical Center and president of the ASRM. She made an additional point of insisting phthalates are potentially dangerous because they are known endocrine disruptors.
What does the independent science say? The findings of ever so slightly diminished male fertility could well be random or at most they point to a very weak association. Even a strong association would not be cause for alarm, as that’s not the same as causation. In other words, from a public health standpoint, this is a classic case of a ho-hum study with contradictory results that did not justify the spate of alarmist headlines.
The data interpretation aside, one wonders about the wisdom of scientists putting much weight on any study that has as its central premise that urine data is an important measure of toxicity. The presence of miniscule levels of phthalates (or BPA for that matter) in urine simply does not have significant health related consequences. Humans consume all sorts of potentially toxic substances, such as the 30+ carcinogenic ingredients in coffee. The liver and other bodily processes render these substances harmless in almost all cases.
Toxicologists and regulators regularly warn the public not to overreact to biomonitoring urine studies. According to the Centers for Disease Control and Prevention, “Phthalates are metabolized and excreted quickly and do not accumulate in the body.” In other words, the temporary presence of minute quantities of a substance in the urine is not necessarily or even likely a danger signal.
Real world research doesn’t suggest humans face any serious dangers from phthalates. Children and pregnant women are considered the most vulnerable populations and are most likely to be impacted by endocrine-effecting chemicals. In its phthalate summary, the CDC cited a comprehensive study conducted in 2004 by the Children’s National Medical Center and the George Washington University School of Medicine that showed no adverse effects in organ or sexual functioning in adolescent children exposed as neonates to the chemical. The same team evaluated infants in a 2010 study and reconfirmed those negative findings. Another recent study has shown that even high levels of phthalates have shown no effect on the genital development of marmosets, let alone humans.
I broached the complicated issue of the research value of biomonitoring data with Germaine Buck Louis, Director of the Division of Epidemiology, Statistics and Prevention Research at the National Institutes of Health, the co-author of the questionable study. Perhaps because it is among the hottest questions in her field—many studies on BPA and phthalates, including her own, would be considered of limited value if the emerging consensus prevails—she refused to respond. “I prefer to wait for the full paper to be out before further comments,” she emailed me.
But even a casual review of the study pointed to another lethal flaw: It does not distinguish between the impact of different types of phthalates, or even acknowledge that there are different substances within the phthalate class with different toxic profiles.
Journalists hype sensational findings even when data are weak
Scientists and regulators but rarely journalists draw distinctions between so-called low molecular weight ones—DEHP, BBP, DBP and DIBP— and high weight ones such as such as DINP, DIDP and DPHP. Despite the public perception and even the assumptions of many reproductive scientists, there are significant differences in chemical attributes, technical performance, end use applications and potential toxicity between various classes of phthalates. Although the potential danger of all classes of phthalates appears minimal, there is general belief that low ones might be more problematic.
The low-weight phthalates, used in personal care products such as cosmetics and perfume and in blood bags and IV tubing are slightly more volatile and can release minute amounts of off gasses. Some regulatory bodies have instituted precautionary bans on low molecular weight phthalates based on rodent studies. Congress has permanently banned three of the low weight phthalates (DEHP, DBP, BBP) in any amount greater than 0.1 percent in children’s toys and certain child care articles.
The long-term regulatory fate of the high-molecular weight phthalates is less sure. The chemicals are ubiquitous, used in PVC/vinyl products as well as in automobile trim, flooring, roofing, hoses, shoe soles, wire and cable insulation, sealants and many industrial processes. From a chemical perspective, high-weight phthalates are more stable and more resilient than low-molecular phthalates.
Under the eye of activist groups and required by order of Congress, the United States Consumer Product Safety Commission (CSPC) research organization known as the Chronic Hazard Advisory Panel or CHAP is expected to issue an updated scientific review any time now. Pending the results of the CHAP review, there now exists a temporary ban on any child-care article that contains more than 0.1 percent of DINP, DIDP or DNOP.
Europe and other countries, which take a broad, precautionary approach to chemical regulation, are actually backing away from tightening restrictions. Last summer, the European Chemicals Agency (ECHA) issued its reevaluation of high molecular weight phthalates, concluding “DINP and DIDP are safe for use in all current applications.” Last year, an Australian review of DINP, relying heavily on CPSC’s own data, concluded that humans did not face any serious health concerns. Those are two of more than a half dozen studies over the past decade that have drawn sharp distinctions between high- and low-molecular weight phthalates, repeatedly finding the high weight ones are safe as commonly used.
One way to distinguish potential junk science from reliable data in the phthalates controversy is whether scientists distinguish in their analysis between high and low molecular versions. Based on a list emailed to me by Dr. Louis, she and her research team did not distinguish between the two types of phthalates both in designing the study and in performing the analysis. It’s not clear they even know the differences exist. Unless they measured these different substances and examined their effects separately, they have no idea what might have caused both an increase in female fertility and a decrease in male fertility. Perhaps one type of phthalate provides fertility benefits and another is potentially harmful. Or most likely, their findings are just statistical noise.
Yet, the problems with this study eluded the ever-hungry sensationalist media, which issued a spate of scare headlines. “There is striking tendency for poor-quality studies—those that appear to point to some adverse effect—to get this kind of attention, whereas much more pain-staking and rigorous studies that find essentially nothing never get this kind of attention,” I was told by Geoffrey Kabat, Columbia University epidemiologist and author of Hyping Health Risks: Environmental Hazards in Daily Life and the Science of Epidemiology. “It’s this inverse relationship between quality and newsworthiness that I find striking.”
In fact, the overwhelming majority of studies over the past decade show that exposure to products containing high molecular weight phthalates poses no serious health risks to children, pregnant women or adults.
What if the CPSC feels pressured to react to junk science studies and news media pressure and extends the ban to even more products? Activists would be thrilled, as they are often indifferent to the economic consequences and the health trade-offs that could result. Plastic products, from flooring to auto dashboards, would still need to be produced; but they would be made with less well-tested and less effective substitutes. A less tested plastic additive would need to be substituted for a phthalate such as DINP or DIDP, both of which have long histories of safe use over the past 40 years.
“The forced conversion to non-phthalates would force reformulation to products that will cost more or offer poorer performance or both,” professor Godwin told me. “The poorer performance could mean reduced product lives. They won’t last as long. Because the substituted additives are more volatile, as the plasticized PVC product ages, it becomes brittle. If this were a childcare article or toy, it could potentially become a choking hazard. If it’s made from organic materials, it could develop an unpleasant oily finish and odor.”
One key application for high phthalates is in house wiring, which could pose an additional hazard. When someone builds a house, the expectation is that the building wire installed into the house, will last a very long time because of the safety risks and the high costs to rewire a house. You hope that as you build, you will outlive the wiring. The current building wire products made with DIDP or DPHP plasticized PVC jackets and trimellitate or trimellitate/phthalate blends for the PVC wire insulation have a long history of safe use. Anything replacing them would not have this kind of safety record.
Are there serious health or safety trade offs? “The new products could also be more hazardous,” Godwin said. “For example some alternatives are more volatile than the higher molecular weight phthalates.”
Is the CSPC even considering the risk of possible substitutes and holding them to the same standards and safety assessments that phthalates have been subjected to over the years.
Advocacy groups, often brandishing scare news reports, try to muddy the regulatory waters, invoking precautionary concerns that all phthalates are potentially dangerous “endocrine disruptors.” Fueled by the misleading hype over phthalate studies—that’s what happened at the reproductive association gathering—CSPC is under increasing pressure from activist groups to make the ban on high-molecular weight phthalates permanent. Will CPSC follow the science or the scares?
There are no comments available.
1150 17th Street, N.W. Washington, D.C. 20036
© 2014 American Enterprise Institute for Public Policy Research