Effect of Dioxin (TCDD) on Sex Ratio After Occupational Exposure

Persistent organic pollutants (POPs) are chemical substances that persist in the environment, bio-accumulate through the food chain, and are deleterious to the environment and to human health (1).  The Stockholm Convention, an international treaty signed in 2001, established a list of the 12 most serious POPs in order to enforce proper management/disposal, at the very least (1).  This “dirty dozen” includes dioxins, a family of industrial byproduct chemicals, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (2).  TCDD, previously linked to reproductive health issues (among other things), is found more abundantly as it moves up the food chain (2).

In August of this year, a study was published in Occupational & Environmental Medicine that studies the effect of TCDD exposure on the ratio of male-to-female offspring of those exposed (3).  The study back-calculated serum TCDD concentration of 244 voluntary participants who worked in an herbicide production plant between 1969 and 1984 (3).  The data ultimately analyzed included 355 births from 127 biological fathers and only 21 biological mothers (3).

While the results of the study found no statistically significant effect of serum TCDD concentration in women, they do indicate that a serum TCDD level above 20 pg/g in men was associated with the birth of fewer boys relative to girls (3).  However, limited studies on the endocrine/reproductive effects of TCDD, an overall scarcity of research in this area, and severe methodological drawbacks (e.g. model estimations of serum TCDD at time of conception), should be considered.

A month later, the Huffington Post published an article entitled “Men Exposed to This Herbicide Chemical May Be Less Likely to Have Sons” (4).  Despite the obvious click-bait nature of the title, the article is reasonably well-written.  The author, Lisa Rapaport, simplifies the science for a non-scientific audience, and includes caveats about sample sizes, contradictory studies, and an overall lack of available research (4).  For example, she concisely defines dose-dependence as, “the higher the dioxin exposure, the bigger the effect” (4).  Fruther, she is critical of the sample size of women in the study, mentions that few studies of this nature have been done, and that some of the others do not observe the same effects.

Rapaport is a member of the Center for Health Journalism, an organization that extensively trains journalists how to approach science in the news. She presents the information effectively while being critical of the underlying science.  As a result, despite HuffPo’s sensationalist nature and several missed opportunities to be even more critical, I give this article an 8/10 for Rapaport’s reasonably critical and efficient approach to the study.

Works Cited

1.    "Persistent Organic Pollutants (POPs)." UNEP. United Nations Environment Programme, n.d. Web. 25 Nov. 2016. <http://www.unep.org/chemicalsandwaste/POPsold/tabid/1059787/Default.aspx>.

2.    "Dioxins and Their Effects on Human Health." World Health Organization. World Health Organization, n.d. Web. 25 Nov. 2016. <http://www.who.int/mediacentre/factsheets/fs225/en/>.

3.    Mannetje, Andrea ‘T, Amanda Eng, Chris Walls, Evan Dryson, Manolis Kogevinas, Collin Brooks, Dave Mclean, Soo Cheng, Allan H. Smith, and Neil Pearce. "Sex Ratio of the Offspring of New Zealand Phenoxy Herbicide Producers Exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin." Occup Environ Med Occupational and Environmental Medicine (2016): 1-6. Web.

4.    Rapaport, Lisa. "Men Exposed To This Herbicide Chemical May Be Less Likely To Have Sons." Huffington Post. Huffington Post, 30 Sept. 2016. Web. 25 Sept. 2016. <http://www.huffingtonpost.com/entry/men-exposed-to-this-herbicide-chemical-may-have-fewer-sons_us_57eea9d7e4b024a52d2ec72a>.

Study finds PCBs disrupt pregnancy

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

How Eating Tuna Can Weaken Your Immune System

Persistent organic pollutants (POPs) are carbon-based chemical substances that remain in the environment over a long period of time. They can be transported over long distances and can bioaccumulate through the food web, storing in fatty tissues of living organisms. POPs are widely distributed over large regions around the globe due to human activity. Effects of POPs includes damage to the nervous system, reproductive system damage, immune system damage, cancer, and allergies (1). Some POPs are also endocrine disruptors, damaging the hormonal system leading to damage within the reproductive system as well as the offspring. Common POPs can include crude oil and petroleum refined products (gasoline, motor oil, kerosene) polyaromatic hydrocarbons (from coal power plants, manufacturing gas plants), PCBs (polychlorinatedbiphenyl ethers), pesticides/ insecticides/ herbicides, detergents, plastics, and alcohols (1). 

On April 21^st, 2016 Emily Gertz from Alternet posted an article titled “How Eating Tuna Can Weaken Your Immune System”. This article was based off of the work lead by Amro Hamdoun. Starting off, the article states that eating any seafood that has been tainted with long-lasting environmental contaminants can weaken the body’s defense system. Emily talked about how the study tested how the exposure to 10 POPs can impact an important protein, P-gp, in animals (3). The purpose of P-gp is to eject toxins from the body but the researchers found that the 10 POPs can weaken this protein’s protective role. Throughout the article Emily provides quotes and facts directly from the peer reviewed article. She states what the purpose of the study was and the conclusions it made. She also gave some background information on POPs at the end of her article. 

The peer reviewed article titled “Global marine pollutants inhibit P-glycoprotein: Environmental levels, inhibitory effects, and cocrystal structure” focused on P-glycoprotein (P-gp) and how 10 different POPs interact with the drug outflow transporter, P-gp (2). The researchers identified specific types of organochloride pesticides, polychlorinated biphenyls, and polybrominated biphenyl ethers which inhibit P-gp in organisms. P-gp is a key protein for xenobiotic elimination in all animals. Within the discussion section the researchers described that the P-gp along with P450 is expressed on apical plasma membranes at sites of toxin uptake such as the intestine (2). The inhibition of P-gp by POPs can cause a decrease in critical cellular defense. P-gp protein was extensively studied with the interaction of inhibitory pollutants, polybrominated diphenyl ether (PBDE)-100 (2). This provided the first view of a pollutant binding to a drug transporter. The structure of P-pg also reviled a high degree of conversion within POPs binding residues. They determined the environmental levels of these POPs in yellowfin tuna from the Gulf of Mexico. Primarily tuna was studied because it is one of the most exported fish in that area. The study concluded that there is an inhibition of the transporters by POPs found in fish (2). 

I feel that Emily did a good job stating the facts and getting to the point of the peer reviewed article but she did leave out many other important facts that the study concluded that she did not include. I wish she would have talked about solving the cocrystal structure of P-gp bound to a pollutant. Also, I believe that Emily should have focused more on P-gp and its inhibition from POPs since this was the main focus of the study. I did like that she included direct quotes from the peer reviewed article and that she did give some further information that was not stated in the article as well including links to other articles involving the same topic. Overall, I would rate this article a 7/10 for the reasons previously stated. 

1) "The 12 Initial POPs under the Stockholm Convention." Stockhold Convention. N.p., n.d. Web. 12 Nov. 2016. <http://chm.pops.int/TheConvention/ThePOPs/The12InitialPOPs/tabid/296/Default.aspx>.

2) Nicklisch, Sascha, Steven Rees, Aaron McGrath, Tufan Gokirmak, Lindsay Bonito, Lydia Vermeer, Cristina Cregger, Greg Loewen, and Amro Hamdoun. "Global Marine Pollutants Inhibit P-glycoprotein: Environmental Levels, Inhibitory Effects, and Cocrystal Structure." Science Advances 2.4 (2016): n. pag. Global Marine Pollutants Inhibit P-glycoprotein: Environmental Levels, Inhibitory Effects, and Cocrystal Structure | Science Advances. 15 Apr. 2016. Web. 14 Nov. 2016. <http://advances.sciencemag.org/content/2/4/e1600001.full>.

3) Gertz / TakePart, Emily J. "How Eating Tuna Can Weaken Your Immune System." Alternet. N.p., 21 Apr. 2016. Web. 12 Nov. 2016. <http://www.alternet.org/food/how-eating-tuna-can-weaken-your-immune-system>.