How endocrine disruptors affect menstruation

2021-09-01

In 2017, a Korean media outlet decided to investigate the chemicals found in commercial menstrual pads, based on the advocacy and awareness-raising efforts of the Korean Women’s Environmental Network, who had pointed out that menstruating people seemed to be developing rashes, discomfort, and even infertility from the pads.

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• Women, gender minorities, and children are most likely to be exposed to endocrine disruptors because of the products they are more likely to use.

• People are exposed to many different types of endocrine disruptors, from phthalates to lead. Many are known to be harmful to human health.

• The solution is not as simple as deciding on acceptable thresholds of chemicals or replacing ingredients. The key question is: How were these materials permitted in the first place?

This group sent samples to reproductive toxicologists Jodi Flaws and Jay Ko at the University of Illinois, where I am also employed. Flaws and Ko found volatile organic compounds and phthalates in every single sample of sanitary pads and disposable diapers they received, and published their results in Reproductive Toxicology. The products they sampled were made in 2017 and came from Korea, the United States, Japan, Finland, France, and Greece; the researchers were kept ignorant as to the sources of their samples as they were conducting their analyses, to avoid bias. Although the quantities of volatile organic compounds were not too alarming—they weren’t too different than what we are already exposed to, and you can reduce them by letting these products air out a bit before using them—the phthalates were another story.

Phthalates, a class of endocrine-disrupting chemicals, are widely known to be harmful to human health. Phthalates are very common in plastics, cosmetics, and apparently menstrual pads, because certain phthalates (there are many of them) can help a substance dissolve or can make plastics harder to break. Women, femme-identified gender minorities, and children are most vulnerable to exposure because phthalates are so often found in the products they are more likely to use: cleaning products, cosmetics, baby toys, and more. (To be clear, this is a general statement based on how gender roles inform and even constrain choices.) Additionally, people who experience incontinence, from babies and toddlers to postpartum people to elders, are going to be exposed to diapers, and menstruating people (including nonbinary people and transmen) to menstrual pads. These put phthalates right up against our thin genital skin.

Endocrine-disruptor exposure also comes from the food we eat: Foods that are encased in plastic (wrapped produce, plastic water bottles) are likely to have absorbed the chemicals used to give that plastic its structure or softness. Some prescription and over-the-counter medicines are even coated in phthalates. When we receive intravenous fluids in the hospital, those fluids have been sitting in plastic made with phthalates, and although these injections do not seem to have significant short-term effects, rodent studies suggest that those literal injections of phthalates can have intergenerational effects on the health of our children and grandchildren.

Whenever I find myself discussing this issue with others, I tend to encounter two main reactions: Either people immediately want to know what they should throw out (and what they should use as replacements), or people throw up their hands at the futility of avoiding endocrine disruptors. I understand and have harbored both of these viewpoints at times. However, I think a third reaction is possible, one where we step back and recognize the broader structural problems that have brought us here. We must consider our varying responsibility and power within those structures that have put all of us at risk, but some of us especially so based on sexism, racism, and ableism, and sometimes just based on physiology. This approach means sitting with this knowledge for a minute, rather than immediately reacting. After all, these endocrine disruptors are not going

Periods on Phthalates

Krakow, Poland, is one of my favorite cities on the planet. It is one of the first places I ever visited on my own, and is the closest city to the rural mountainous region where I have conducted much of my fieldwork on menstrual cycles. I remember being picked up at the airport on my first visit in 2002 by my mentor and collaborator, public health researcher and anthropologist Grazyna Jasienska of Jagiellonian University, in part because of where she had parked in the city. Jasienska lived in a lovely apartment in the Old Town, and as a resident, she had a special permit to drive and park in the central part of the city. Although some of the initial decisions to limit traffic in Krakow were about tourism and support for local residents, one of the by-products of these driving and parking restrictions has been that it may reduce some local pollution. Because Krakow sits in a valley, air pollutants can drift in from surrounding industry and linger, and traffic emissions can stagnate there as well. The Old Town area is gorgeously preserved, with stone buildings that are many hundreds of years old and a city center with churches, flower sellers, and booths of traditional souvenirs such as amber jewelry and embroidered blouses. Air pollutants are bad for the buildings, bad for the inhabitants, and bad for tourism.

The air pollution from traffic, particularly from higher-emission cars, comes from particulate matter (bits of dust, soot, and smoke of varying origins), sulfur dioxide, carbon monoxide, and nitrogen oxides. (See “Air Pollution and Sunlight Q&A,” January–February 2016.) A 2017 paper in the International Journal of Environmental Research and Public Health by Anna Merklinger-Gruchala of Krakow University, Jasienska, and Maria Kapiszewska, also of Krakow University, looked at these different types of air pollution together, to try and understand whether fossil fuel combustion from industry and heating, traffic fuel emissions, or both together produce cumulative effects on the menstrual cycle.

The sampling period was 2001 to 2003, right around the time of my first visit to Poland. My colleagues looked at the air pollution measures in Krakow at that time, based on municipal ecological monitoring data by the state, and menstrual cycle characteristics from 133 research participants living in the city. In this study, there were no effects on the menstrual cycle when considering any one pollutant on its own. However, the authors found that particulate matter and sulfur dioxide exposure together were associated with a shortened luteal phase (the second half of the menstrual cycle, starting at ovulation and ending at menses). These pollutants derive mostly from fossil fuel emissions—the kind that come from older heating units and factories. The effects on the menstrual cycle of the other pollutants studied—carbon monoxide and nitrogen oxides—were not statistically significant in this sample.

The authors mathematically estimated that exposure to air pollution at the level found in this study led to a shortening of the luteal phase by a third of a day. Given that nearly all embryo implantations occur within a three-day window in the middle of the luteal phase, a disruption by a third of a day could represent a significant biological event. A shorter luteal phase also means a shorter menstrual cycle, which means in the long run more ovulations and more periods. Some research has suggested that a higher frequency of ovulation may be associated with an increased risk of reproductive, particularly ovarian, cancer.

A number of other papers have looked at the effects of air pollution on fecundability (the probability of conception in a given cycle), fertility (number of offspring), and fetal and infant health, and they have all reached similar conclusions. Several studies looked at people who are occupationally exposed to certain pollutants. Nail salon workers experience occupational exposure to phthalates, phthalate alternatives, and volatile organic compounds; recent work published in Environmental Science and Technology found the problem may lie not only in nail product formulations but also in nail salons not adhering to proper ventilation guidelines. What’s more, the volatile organic compounds emitted from salons are probably contributing to volatile pollution more broadly, according to a 2019 paper in Indoor Air. Traffic police are exposed to particulate matter and other airborne pollutants; these subjects have been found to have lower estradiol concentrations (a type of estrogen), and higher follicle stimulating hormone concentrations (a hormone important to ovulation) than controls who are less exposed. Another study, published in 2017 in Human Reproduction, looked at mostly middle class white women from Michigan and Texas, and even with their relatively low exposure to air pollution compared to other people, the authors found some weak associations between acute exposure to some pollutants and how many cycles it took for couples to conceive. Similar research, published in 2018 in Human Reproduction, has shown reduced in vitro fertilization rates with increased exposure to certain air pollutants.

Then there are the endocrine disruptors in our water. Many communities in the United States are exposed to lead, cadmium, arsenic, and other heavy metals in the water they drink. (See “Arsenic, the ‘King of Poisons,’ in Food and Water,” January–February 2015; “First Person: Mona Hanna-Attisha,” September–October 2019; and “Moving Forward After Flint,” May–June 2016.) In many parts of the country, these exposures are considered to be under an acceptable threshold by, say, the U.S. Centers for Disease Control and Prevention (CDC), but not necessarily by the members of those communities. The CDC’s reference value for the acceptable quantity of lead in the blood, for instance, is 5 micrograms per deciliter and under. This is a recent shift from 10 micrograms per deciliter and under, and other experts recommend moving down this value even further to 2 micrograms per deciliter. Experts at the CDC and elsewhere are clear that there is no actual acceptable amount of lead or any other endocrine disruptor in the body: The tightrope they are walking is one of risk assessment (more on that later).

I found examples in Korea, Mexico, Canada, and the United States where lead exposure that led to a blood concentration of less than 5 micrograms per deciliter still had a negative effect on children’s cognition, growth, and development. And despite the known risks, much higher exposures are experienced by kids in Nigeria whose cough syrups are often contaminated with lead, or by child laborers in Pakistan who work in battery recycling plants, an occupation with significant exposure to lead. These kinds of effects, from learning disabilities to shorter stature to delayed growth or menarche (age at first period), have downstream effects. Although lead is discussed most frequently in terms of the significant harm it causes to child development, this endocrine disruptor can also influence the reproductive systems of adults. Lead exposure does not seem to lower the concentrations of estrogens in the body; instead, it interferes with estrogen receptors in a way that can block ovarian follicle development or embryo implantation, and suppress hormone secretion during puberty.

From here, we could find ourselves going back to where we started: the endless endocrine disruptors found in plastics, cleaners, cosmetics, and food. Bisphenols and phthalates, parabens, polychlorinated biphenyls, heavy metals, and all sorts of other chemicals are in our pesticides, packaging, and pore-refining serums. (See “Plastics, Plastics Everywhere,” September–October 2019.) Exposure to some endocrine disruptors seems to delay menarche, yet exposure to others largely accelerates it. Phthalates and bisphenols in particular are implicated in endometriosis and endometrial cancer because both, as weak estrogens, can disrupt the natural estrogen-to-progesterone ratio in the body and therefore encourage extra growth of uterine tissue. Phthalates, even at lower doses, influence adult reproduction in mice. Most of us are exposed to many different types of endocrine disruptors that may all exert slightly different and even opposing effects, so it is hard to say for sure which ones cause the most harm, or, if you are a company relying on these chemicals, whether they really cause any harm at all.

Phthalates and bisphenols are implicated in endometriosis and endometrial cancer.

Endocrine disruptors even have effects across generations. In the case of lead, much of it is stored in bone. Because bone turnover increases in pregnancy and because lead can pass through the placenta, fetuses can experience significant lead exposure if their mothers were previously exposed. Researchers have just started measuring the epigenetic effects of phthalates across the generations—that is, the ways in which the expression of genes can be modified, and those modifications passed down, even without changes to the DNA itself. Epigenetic effects have the potential to occur not only in, say, a prenatally exposed generation, but also in the unexposed offspring of the following generation: the grandchildren of the originally exposed parents. Exposure to endocrine disruptors, then, can affect generations of children who are completely unexposed, which means that even with tighter regulation today, some populations may continue to experience disruptions of development, puberty, menstrual cycle function, and reproduction for years to come.

Many of us in the United States, with our individualistic culture, continue to think of these problems as ones that affect individuals, and therefore as having individual solutions. In addition to the fact that I now vent my disposable menstrual pads in my bathroom to let them release volatile organic compounds before I place them against my body, I have switched my toddler to a combination of reusable and disposable bamboo pullups, and my kids now eat off stainless steel instead of using plastic plates and utensils. But you might also have noticed that although many of these exposures come from household objects we are bringing into our homes, other exposures are not up to us. Air and water pollution get into our homes and can be found not only in our food and water but also in the dust under our beds. There are ways our built environment, landscape, and neighborhoods can protect us, but even here we can see that gender and race continue to play a role in who can access risk-reducing resources.

Going Green

When I was in graduate school, the nearest park with running paths was eight blocks from my apartment. Between union organizing, teaching, and lab work, I had a lot of long days and so I often wanted to work out early. But the nearby East Rock Park in New Haven, Connecticut, was a bit creepy to run in alone, so I tended to go to the gym or run with a friend; even with a friend along, we often opted to run at the nearby high school track instead of going to the park. Green spaces are supposed to be good for us: They provide ways to reduce air and noise pollution, avoid indoor pollution, and get some physical activity. These are all good for menstrual health. But who can use them? Women, gender diverse, and gender nonconforming runners do not feel comfortable running alone in many settings, for good reason: They have both legitimate and acculturated fears for personal safety. I’ve had cars pull over and men yell at me to smile; an acquaintance recently shared a time a driver pretended to hit her in a crosswalk. And sexism is not the only factor that can put you at risk when you try to enjoy the outdoors. Tamir Rice was playing in a park. Ahmaud Arbery was going for a run.

Green spaces are supposed to be places for people to reduce their psychosocial stress and improve their mental health, but people who are not men don’t necessarily experience them that way. In one study, published in 2014 in Landscape and Urban Planning, researchers had participants go through a classic stress test, and then exposed them to realistic, three-dimensional videos of neighborhoods with varying amounts of greenery to measure whether greenery exposure had any effect on participant recovery from the stress test. The researchers found that the men who participated had mild improvements in recovery, but the women did not. In another paper, published in 2014 in the Journal of Epidemiology and Community Health, researchers looked at green space availability within neighborhoods as well as a number of mental health indicators: Again, there were different relationships between mental health and green space by gender. For men, the relationship was linear, meaning the more green space in their neighborhoods, the better their mental health. For women, however, the relationship was U-shaped, where better mental health was associated with moderate rather than low or high green space. The greatest benefit of green space for mental health in men was seen starting in their early thirties and remained fairly stable throughout their lives; for women, there was no benefit of green space until their mid-forties, and the benefit then increased with age. As a woman in my forties, I can say that my experience with street harassment has dropped off considerably, and I can’t help but wonder if that helps explain the gender difference.

When it comes to endocrine disruptors, one of the main things a green space should do is serve as a literal buffer between a person and these pollutants. And this buffering has been supported in two recent studies published in Environmental Research, one out of the United States and one out of Iran. These papers have shown that exposure to air pollutants is associated with lower anti-Müllerian hormone levels—this hormone is often used as a rough estimate of one’s “ovarian age,” and a lower value of anti-Müllerian hormone generally corresponds to fewer eggs. This finding matches the aforementioned literature that many endocrine-disrupting pollutants can compromise menstrual health.

Both studies have also shown that green space in one’s neighborhood is associated with an increase in anti-Müllerian hormone; in the U.S. sample, the green space effect was only true if the air pollutants were also low. Air pollution and green space are differentially distributed in the United States by socioeconomic status and race. So, not all communities with access to green space are able to reap their health benefits (which extend far beyond buffering from pollution exposure), because of the ways air pollution or safety concerns nullify any of the effects.

Is Resisting Phthalates Futile?

If any of you are like me, you’ve hit this portion of the article and wanted to go on a shopping spree to replace all the plastic in your home. A menstrual cup might reduce one’s exposure to some endocrine disruptors—but only when one buys the most expensive cups, because medical-grade silicone is not a strongly regulated material and in some cases could still contain endocrine disruptors. These cups can still leak, so a heavier bleeder will need a backup, but most disposable and many reusable backups also contain plastic. Green space will help—but only if one is rich enough to live in a lower-pollution area, and if one’s body (usually white, usually male) is not threatened regularly. Maybe some of these things will reduce your exposure.

But this framing around individual product replacement is a scam for two reasons. First, this idea of personal responsibility tends to be gendered, falling in particular on women and gender-diverse people. Women often perform the labor of minding risks and trying to reduce them, and many studies of intergenerational harms are framed in ways that blame mothers for their own exposures.

The second reason is that this individual framing misses out on the chance to notice the structural one. To see the structural problem clearly, it helps to look back to a time when plastics were not widely disposable or a major source of pollution.

The temptation so often when dealing with pollutants is to imagine an “away” where they do no harm.

In 1956, Lloyd Stouffer, then-editor of the magazine Modern Packaging, encouraged a room full of attendees at a conference of the Society of the Plastics Industry to start thinking about one-time use plastics as the key to get continuing customers. “The future of plastics is in the trash can,” he said, meaning that disposable plastics would gain more consumers and make more money than multiuse plastics that one buys only once. In 1963, Stouffer wrote a review for the Society’s annual conference reflecting on that talk and where plastics had gone. “It is a measure of your progress in packaging in the last seven years that this remark will no longer raise any eyebrows. You are filling the trash cans, the rubbish dumps and the incinerators with literally billions of plastics bottles, plastics jugs, plastics tubes, blisters and skin packs, plastics bags and films and sheet packages—and now, even plastics cans.” He continued, “The happy day has arrived when nobody any longer considers the plastics package too good to throw away.”

Because that’s just it, isn’t it? The temptation so often when dealing with pollutants is to imagine an “away” where they do no harm. But as Max Liboiron of Memorial University in Canada says in their recent book Pollution Is Colonialism, there is no “away.” (For more on Liboiron’s work, see “How Climate Science Could Lead to Action,” January–February 2020.) People live near landfills; people rely on polluted waterways for food and income. Pollutants from landfills leach into groundwater. We are at the point where we have polluted our planet, affecting not just our species but entire ecosystems.

In the early days of conservation efforts by settler scientists in the United States, researchers applied locational data on the Ohio River to our understanding of how pollution gets into (and supposedly out of) our water more broadly. They developed a threshold model, where there is a quantity of pollution you can pump into a river, under which the river can still recover. As Liboiron points out, both the eager corporate development of disposable plastics and the well-meaning conservationists’ threshold model assume one has access to Indigenous Land to put pollutants. Here, Liboiron does not just mean current tribal lands and reservations, but rather the land that was originally occupied by Indigenous peoples, and that settlers took from them. The assumption that this land is available to take and use as settlers wish, and that they consider some parts of the land acceptable for storing pollutants (to protect some but not all people, places, and beings), undergirds the entire mitigation strategy of the United States. In other words, the disposable model from the plastics industry and the threshold model from conservationists are both permission-to-pollute models that never really asked permission.

Pollution, then, is an ongoing and essential component of colonialism. “Colonialism is more than the intent, identities, heritages, and values of settlers and their ancestors,” Liboiron writes. “It’s about genocide and access.” And although endocrine disruptors are everywhere, they are unevenly distributed, causing additional violence toward Indigenous communities.

When scientists participate in pollution science, or in a discussion, say, about phthalate exposure, we enable a process of what Patricia O’Brien, in her classic 1993 Professional Biologist article “Being a Scientist Means Taking Sides,” called assimilative capacity assessments rather than alternatives assessments. An assimilative capacity assessment would ask how much pollution scientists have decided the planet can tolerate, whereas an alternatives assessment would entail imagining a path where scientists and nonscientists together decide that no harm to people, other beings, or land is acceptable. As of now, most of the replacements for phenols and phthalates appear to be as bad, if not worse, than the originals. An alternatives assessment here is not as simple as replacing an ingredient. We need to reconsider the ubiquity of endocrine disruptors in our society as a whole.

Taking this broader view, you could consider getting a menstrual cup (not everyone can tolerate them and it takes time to find the right one), and also teaching others to use them, because there is a significant learning curve. Maybe get a water filter if you can afford one (the ones that filter lead can be expensive), and also discuss with your local politicians about allocating more funds to your community’s infrastructure. Changing the frame allows us to see and act in solidarity across many communities and constituencies affected by the production, distribution, and dumping of polluting substances. What do you see when you change yours?

americanscientist.com, 1 September 2021
; https://www.americanscientist.org