Organochlorines are a group of compounds with similar chemical
structures, which includes polychlorinated biphenyls (PCBs), heaxacholorabenze
(HCB), and dichlorodiphenyldichoroethylene (pp’DDE), a metabolite of DDT (1).
They are persistent in the environment and can last for years to decades in
soil and lake sediments. These compounds are classified as endocrine disruptors
(EDCs) and are capable of interfering with normal tissue and reproductive organ
development, especially during critical periods of development across the life
cycle (3). It is hard to study the effects these chemicals have on the
endocrine system because many chemicals in the same class can exert different
effects. For example, different PCBs have been shown to have antiestrogenic,
estrogenic, androgenic, or antiandrogenic properties (3). There is research to show that PCBs, HCBs, and
pp’DDE disrupt the female reproductive system through multiple pathways including
ovulatory dysfunction and menstrual cycle disturbances which affect a woman’s
ability to get pregnant.
Medicalxpress.com published an article titled Study finds PCBs disrupt pregnancy on
November 9, 2016. Medicialxpress “is a web-based medical and health news
service that is part of the renowned Science X network”, which includes Phys.org.
The article described the results of a study
conducted by researchers at the University of Albany who sought to understand
the relationship between women’s exposure to organochlorines and impacts on
their menstrual and ovulary cycles. The researchers took samples from women in
the Akwesasne Mohawk Nation, which is a territory adjoining New York, Ontario,
and Quebec (2). Their land is located on the St. Lawrence River next to three
industrial sites where large amounts of PCBs where dumped into the river and
its three tributaries. One of these sites is a National Priority Superfund Site
and two are New York State Superfund sites (3). The river is so polluted that in 1980 the US FDA warned people not to eat
fish from the local waters or other wildlife that surround the river. Unfortunately,
the Akwesasne people relied on the fish and wildlife around the river as a
large part of their diet before the advisory went into effect (3). Since the
80s the Akwesasne people have expressed health concerns from their
environmental exposures. For years, women have reported problems with conceiving
and early pregnancy loses (3). The study found that most women had normal menstrual
cycles but certain organochlorines were associated with a risk of not ovulating
during their menstrual cycle. Concentrations of certain PCB congeners were associated
with decreased probability of ovulation. For every unit increase in a certain
class of PCBs, there was a 2.4 times greater chance that a woman would have a
non-ovulatory cycle (3). The researchers not find the same association for HCB
or pp’DDE and non-ovulatory risk.
The Medicalexpress article failed to mention that the
researchers looked at the relationship between exposure to HCBs and pp’DDE and
ovulation status. Instead they chose to discuss only the positive association
between exposure to PCBs and decreased ovulation status. The article also states
that the researchers believe their findings can be extended to all women in the
US, which is not something the researchers concluded in their study. I think it would be a stretch to extend these
findings to all US women, given that all US women do live in areas with high
PCB levels or rely on their dietary needs from areas with high exposures. Additionally,
Medicalexpress makes it seem like exposure to these PCBs and a obesity lead to
a decreased chance of ovulation, when regardless of exposure to any of the
toxicant studied obsese women have a lower probability of ovulation. My biggest
issue with the Medicalexpress article is that they wrote that PCBs can impair
the ability of women to conceive when the article results found that PCBs impair
ovulation during a menstrual cycle. Although conception and ovulation both have
to happen in order for a woman to be pregnant, conception is defined as “the inception
of pregnancy” or “fertilization”, while ovulation is defined as producing eggs
from an ovary (4)(5). Saying that PCBs impair the likelihood of conception leaves out
the potential impacts PCBs could have on men and their sperm, which is also a
necessary component for conception.
Given that medicalexpress promotes their site as a
health news service I would give the article a 5/10. The article mostly uses
quotes from the peer-reviewed journal, left out the fact that the researchers
also looked at HCBs and pp’DDE, and did
not come to many of their own conclusions. When the journal did make
conclusions, they seemed to me to be slightly inaccurate or misleading.
References
1. Center for Environmental Research & Children's
Health. (2011, December 13). DDT Pesticides, PCBs, & Other
Organochlorines. Retrieved from
http://cerch.org/environmental-exposures/ddt-and-other-organochlorine-pesticides/
2. Medicalexpress. (2016, November 9). Study finds
PCBs disrupt pregnancy. Retrieved from
http://medicalxpress.com/news/2016-11-pcbs-disrupt-pregnancy.html
3. Gallo, M. V. (2016). Endocrine disrupting chemicals and ovulation: Is there a relationship? Enviornmental Research, 410-418.
4. Dictionary.com. (2016). Retrieved from http://www.dictionary.com/browse/post-conception
5. Dictionary.com (2016.) Retrieved from http://www.dictionary.com/browse/ovulate
Interesting topic Stacey! I have to agree with your rating of the Medicalexpress article. Although the researchers made no conclusions about exposure to HCBs and pp’DDE, this was still an important part of the study. It feels as if the author of the Medicalexpress article cherry-picked the most shocking result and used that to their advantage instead of providing readers with a true representation of the entire study.
ReplyDeleteGreat choice on topic! I also thought it was interesting that the Medical express article made their own conclusions about how these findings could be related to all women in the United States. I definitely think that the Medical express authors would definitely need to back up this conclusion with further data and analysis.
ReplyDeleteI agree that they should have backed up their claims especially since medicalexpress claims to be more a scientific journal
DeleteI'm curious to why the HCB and pp'DDE did not show any non-ovulatory risk. The chemical structures are different between the PCBs, HCBs, and pp'DDEs, but not overly different. What property or function makes PCBs most effective?
ReplyDeleteI don't know exactly how to answer your question because I'm not super familiar with the chemistry behind all these chemicals. But the authors of the journal article wrote a little bit about this in their discussion. The authors were also surprised to find that HCBs and pp'DDE did not affect ovulatory status while the PCBs did because they all chlorinated compounds. The best answer I can give you is that a lot of endocrine disrupting chemicals can act through many different mechanisms (estrogenic, anti-estrogenic, androgenic, and anti-androgenic) and when someone is exposed to more than one of these chemicals a different result may be seen than when someone is just exposed to one singular chemical.
Deletenice post! its interesting to see how different types of chemical can influence the body hormonally. I agree that the article left out key information that the peer review article included. It would be interesting to see how these chemicals could influence the male reproductive system.
ReplyDeleteI agree. I hope someone looks at the men in this community to see if they are any changes in their sperm quality/quantity and if it affects women getting pregnant.
DeleteWith studies like this one, it's always dangerous to extrapolate data to a larger population than the one studied. Like you mentioned, though, it's interesting that the researchers don't actually make that leap, but the authors of the popular science article. This is especially strange since the website is a science-based source. One thing that I think would be interesting in the study would be to look at some other organic pollutants that are created as byproducts of industrial operations. If any of those were present, it might also have affected their results. Nice job!
ReplyDeleteYes I agree. Medicalexpress doesn't seem like a very legit science-based news source to me but I didn't look at any of their other articles. I didn't think about that. I wonder if there were any other chemicals that companies dumped into the St Lawrence River. I know they chose they three chemicals specifically because the companies polluted the river with these.
DeleteI liked this post! Very timely with increasing awareness of the ubiquitous and persistent nature of these chemicals in our environment (and in our bodies).
ReplyDeleteIssues like these remind me how important the Clean Water Act was and how much the environment improved after it went into effect. Apparently General Electric dumped between 500,000 and 1,500,000 pounds of PCB's between the 40's and 70's and fought really hard to avoid doing clean up. Craziness.
Yes that is crazy and unfortunately these PCBs are probably still present in the environment today since these chemicals tend to stick around for a long time.
DeleteGoing off of Josh's comment, when I first read the post I didn't immediately think that these different classes of compounds were all that structurally similar. In fact, being chlorinated is the only thing they have in common. Generally with halogenated organics the concern is the formation of reactive radical species due to carbon - halogen bond homolysis (we talked about this in the context of the atmosphere). However each of these species are examples of aromatic or vinylic carbon - halogen bonds, which have higher bond dissociation energies (BDEs) than aliphatic carbon - halogen bonds. If simply being chlorinated was the issue then all three should have a deleterious effect, and they don't as the study showed. I'm guessing there's a different mechanism at play here that differentiates the biphenyl analog from the benzene and stilbene analogs.
ReplyDeleteIt is interesting to see that this is the presumably the first study that has been done on establishing a relationship between PCB levels and human ovulatory patterns. Although, like you mentioned, the author of the medxpress article took too big of a leap in jumping to the conclusion that these studies should apply to all women in the US facing PCB exposure. Without a larger and more diverse sample population, other variables (ex: genetic effects, eating habits) that are specific to this ethnic group of residents may likely bias the results of this study.
ReplyDeleteHi Stacy, nice post. I agree with your modest rating - I think a media source that specializes in medical and health-based news should be more careful in the conclusions they draw. Here I think they purposefully phrased their article to be more fear-inducing than education or informative. I liked how you clarified that exposure to PCBs does not prevent conception, just ovulation (assuming that if there was ovulation, the chances of fertilization wouldn't vary significantly between women exposed/not exposed to PCBs). I also agree with Lindsey's comment that it would be interesting to see how PCBs may affect men's health. I am also curious as to how to the birth rate of the Akwesasne Mohawk Nation changed after 1980.
ReplyDeleteThis is quite an interesting article. I think that currently there are many other situations throughout the country that is similar to this story. For example the Pennsylvania Keystone pipeline that was not built as a result of it running through tribal land and the fear that it would disrupt natural resources that they rely on. And now the Dakota Access Pipeline is a big issue as well. They believe that again this pipeline can disrupt natural resources that the tribe for generations has relied on (among other things). I think this research article is a testament to their concerns.
ReplyDelete