Endocrine Disruption In Scientific Research

The topic of endocrine disruption, and the potential consequences for human health, is a popular area of investigation for many scientific researchers. Endocrine disrupting chemicals (EDCs) are compounds that have the capability of modifying hormone signaling while possibly effecting the development of both the nervous and reproductive systems, as well as enabling the development of cancer (Site 1). Of all the possible EDCs, phthalates seem to be one of the best-studied and most habitually encountered EDC. According to a study that investigated EDCs and asthma-associated chemicals in consumer products, phthalates are commonly used as solvents in personal care products, adhesives, detergents, lubricants, as well as pesticides despite the short

half-life (Dodson et al., 2012). Nonetheless, phthalates are most commonly known for their strong association with plastic-derived products that are regularly found in the environment (site 1). Due to the diversity in phthalate locality, potential routes of exposure include: ingestion, dermal, inhalation, intravenous, house dust, as well as developmental and early-life exposure (Dodson et al., 2012). Therefore phthalates, in particular, have a variety of negative health implications including susceptibility of/to developing asthma, which is why research is being done to investigate the association between EDCs and respiratory disorders (Gascon et al., 2014).
Whyatt et al. (date) is an epidemiological study that investigates exposure to phthalates, during periods of susceptibility, amongst an inner city population of women and children. This study explores the relationship between phthalate exposures with/and the potential development and further diagnosis of asthma in children (Site 2). Though evidence that links phthalate exposure to the proposed adverse effects on respiratory health are limited, several researchers have suggested the possible interference of phthalates with cytokine expression, their association with oxidative stress and/or other epigenetic mechanisms (North et al., 2014). Furthermore, the ubiquity of phthalates, in addition to the increasing knowledge presented in studies such as the study reviewed and the concerns they pose to human health have resulted in clinicians taking preventative measures by educating and counseling patients in attempt to limit their phthalate exposure (North et al., 2014).
The objective of this study was to investigate the possible association between asthma-diagnosed children and prenatal exposures to butylbenzyl phthalate (BBzP), di-n-butyl phthalate (DnBP), di(2-ethylhexyl) phthalate (DEHP), and diethyl phthalate (DEP) (site).

It was hypothesized that exposure to phthalate metabolites DnBP, DEHP, DEP and BBzP would be linked to asthmatic children (cite). Three hundred inner-city women, along with their children, participating in the Columbia Center for Children’s Environmental Health longitudinal cohort were recruited to participate in the current study. In the aforementioned women, phthalate metabolite concentrations were measured using a spot urine sample during the third trimester, as well as from the children at ages 3, 5, and 7. The urine samples were then sent to the CDC for further analysis of the four metabolites formerly mentioned. At 5, 6, 7, and 11 years of age, information was gathered from the mother via a reliable questionnaire pertaining to the asthma-like symptoms of their child (cite). Additionally, a pulmonologist and allergist assessed the children following the first maternal account of wheeze and/or any other respiratory symptom, and/or the use of an asthmatic inhaler in the previous 12 months on recurrent follow-up questionnaires. During examination, physicians used standardized diagnostic criterion to classify the children as having or not having present-day asthma (site). Contrastingly, the children who hadn’t

reported wheezing or any asthma-related symptoms, at the time of the most recent negative questionnaire, were categorized as non-asthmatic. Additionally, relative risks controlling specific gravity and prospective confounders were estimated using regression analyses. Also, specific. Of the 300 children participating in the study, 154 children were subsequently examined by a physician due to reports of wheeze, other asthma-like symptoms and/or due to use of an inhaler. Moreover, the physician diagnosed 94 children as having current asthma and 60 were categorized as not having current asthma while the residual 154 children were characterized as non-asthmatic. There were significant findings indicating an increase in prenatal BBzP and DnBP concentrations of children with a history of asthma-like symptoms and/or children categorized as current asthmatics in comparison to lower concentrations found in non-asthmatics. Finally, children with maternal pre-natal BBzP and DnBP metabolite concentration falling within the third versus first tertile, results revealed a 70% greater risk of having current asthma (cite).
This study is the first to examine the association between pre-natal exposure to phthalates and childhood asthma; therefore, this study does not contradict any other findings (Whyatt et al., 2014). Instead, previous studies have investigated pre-natal phthalate exposure and the possible association with adverse developmental effects such as testicular disease, pubertal abnormalities, obesity, and ovarian disease acting via epigenetic mechanisms in the murine model (North et al., 2014). Additionally, few epidemiological studies have suggested a potential, but indefinite, relationship between phthalate exposure and asthma (Whyatt et al., 2014). However, the results of this study build upon recent reports of a Taiwanese study demonstrating an association between children, of age 6-9, with a parenteral-reported account of wheeze and increased urinary phthalate concentration (Whyatt et al., 2014). Finally, this analysis adds to the results of an earlier study indicating an increase in lung inflammation and oxidative stress, as well as exacerbation of allergic disease in children age 5-10 (Kato, et al., 2013).
The data that is presented in this study supports the author’s original hypothesis whilst allowing a feasible way to test the hypothesis. The authors had a sufficient sample size and suitable methodology to successfully carry out this study. Additionally, the discussion was extremely detailed, the results were interpreted well, and the authors did a great job making connections between their findings and the findings of other studies investigating similar relationships. However, the design of this study had some drawbacks too. As the authors mention, the misclassification of exposure groups was possible because only a single sport urine measurement of metabolite concentration was used. Also, the authors mentioned that some data was missing or lost due to the lack of follow-up by the participants, which could alter the data. Lastly, the urine samples collected from the mother were obtained during the third trimester, which may not be the most critical window of susceptibility.
The strengths and weaknesses of this study are also important to note.

This study was only executed in the inner city, which would limit the diversity of the population being tested. Furthermore, the authors include a table representing the characteristics of the participants and one can see that the location of the study only includes African American or Dominican participants. Therefore, the lack of ethnic diversity prevents one from generalizing the results across all other ethnicities. Lastly, the authors screened the women participants prior to involvement in the study. The authors only wanted women who were non-smokers, which is another weakness because including these women could have potentially shown a distinct difference between developing asthma as a child of a non-smoker versus smoker. Contrastingly, this study had several strengths. The authors used numerous sources to support the background information provided in the beginning of the paper, which was important because it demonstrates the extensive research they’ve done on the topic. Additionally, the authors mentioned and adjusted for potential confounders that would affect the results of this study, which further validated the results. Also, the overall presentation of the paper was very useful to the audience. For example, the subdivisions underneath the results section were helpful because it allowed me to view the results of each category separately instead of having them presented all at once in one long

paragraph. Lastly, the authors presented their results in both figures and tables; however, the figure presented the data the most efficiently. In comparison to the hectic table full of numbers, the figure presented the data in a way that is easily understood.
As Whyatt et al. acknowledge, this is the first study of its kind to investigate pre-natal phthalate exposure and child asthma risk; therefore, replication is required to validate results. Additionally, it is important to investigate the association between phthalate exposure and respiratory distress nation-wide instead of being limited to one region of the country like this study. Also, this study indicates the increased risk of exposure to phthalates in the inner city, however, it would be interesting to execute the same study in rural regions and compare the results. As author (date) mentions, phthalates are one of several EDCs that have been studied for their potential link to adverse effects on respiratory health. Therefore, studying the effect of these EDCs together, as a whole, would be an interesting experiment in the future because the mixture of EDC exposure may have more effect on respiratory health than one EDC alone. Lastly, future experiments that utilize animal models would be useful to better understand the mechanism used by the aforementioned EDCs.