Ethical Implications of fMRI In Utero

By Molly Ann Kluck

Image courtesy of Wikimedia Commons.

When my neuroethics mentor approached me with a publication from Trends in Cognitive Science called “Functional Connectivity of the Human Brain in Utero” (1) in hand, I was immediately delighted by the idea of performing an ethical analysis on the use of functional Magnetic Resonance Imaging (fMRI) on fetuses in utero. As of right now, I’m still conducting this ethical analysis. 

Using fMRI to look at human brains as they develop in utero is groundbreaking for a couple reasons. For one, there is a vast difference between the fMRI method currently used to investigate developing brains and previous methods that were used to examine fetal brain development. Research on developing brains had utilized preterm neonates, or babies born prematurely. While these data are valuable, there are issues with validity associated with this method: early exposure to an abnormal environment (e.g. being in the intensive care unit, where many preterm babies go after birth, being in an MRI machine, etc.) for a fetal brain, incomplete exposure to the essential nutrients and protection offered by the womb, and the plasticity of the fetal brain all can cause preterm neonates to experience differences in brain development (2). An accurate map of the brain as it typically develops will not be truly accurate if it is produced solely using preterm neonates. However, surveying a developing brain while it is still in utero, as can be done with fMRI in utero, is a different matter altogether. The chances of this research providing a more accurate picture of the developing brain increase due to the uninterrupted development of the fetus in utero. 

Secondly, the sheer amount of insight that can be gained by performing fMRI in utero opens doors to talk about consciousness. For example, fMRI allows for the functional connectivity of different brain structures like the default mode network (DMN) and the cognitive control network (CNN) to be observed. The DMN includes the connected regions of the brain thought to work together when the brain is at rest and is an area of interest for research on various mental disorders such as autism (3). The CNN on the other hand includes the connected regions of the brain that are active when you are exerting cognitive control over your thoughts and actions (12). Both of these functionally connective areas are of interest when exploring what sentience, consciousness, and (potentially) disease arise from. 

Image courtesy of Flickr.

Using fMRI in utero would assist in providing an accurate picture of how brain connectivity develops and would give insight into when these areas become operational. Potentially, attributes like "sentient" and "conscious" could be accurately applied, or conversely, removed from fetuses at specific developmental stages. The idea of fetal sentience would perhaps change the conversation about the way fetuses are popularly considered. Killing a sentient creature isn’t a particularly savory thought, and recently it’s only been a best guess as to when a fetus becomes sentient (10). With fMRI leading the charge on understanding when structures in the brain connect to generate sentience, the exact moment when a fetus becomes sentient, or the developmental stages in which degrees of sentience appear may become clearer. This would inform everything from policy on abortion to women’s health care and fetal moral status. Beyond the observation of sentience, there is evidence that a connectivity difference may be seen in adults with neuropsychological disorders such as ADHD (4) and schizophrenia (5). If the underlying structures for brain connectivity are understood, these disorders may be predicted as early as in the womb, which would make fMRI a relevant diagnostic tool that could be used in utero. 

An early diagnostic tool for neuropsychological disorders may also inform the abortion debate. A pregnant woman who is informed that the fetus she’s carrying will be born with a disorder may choose to abort (14). There are some who would claim it is her duty to do so (11) and others who would claim that selecting a fetus based on this potential for neurodevelopmental difference or disorder is a type of discriminatory act (12). 

As the scientific community continues to explore these possibilities and performs fMRI studies on pregnant women and their fetuses, the safety of the test subject (i.e. the pregnant mother) should be the priority. Some situations may place a pregnant woman at a higher risk of harm or stress than a non-pregnant woman would experience in the same situation. Fetuses are also vulnerable to these harms or stressors since a danger to the mother results in danger to the fetus (2). Three potential risks to the fetus are heat, sound, and stress due to multiple fMRI sessions. These three risks could be encountered by the fetus multiple times throughout the pregnancy, should the mother be enrolled in fMRI research for the duration of her pregnancy. For example, heat exposure in fMRI scanning may be difficult for a fetus to tolerate since fetuses are incapable of regulating body temperature (9). In the fetal stage, the growth of important structures of the fetus, like systems of muscles and nerves, can be reduced by abnormal exposure to heat. It has been noted that the nervous system may develop with defects due to heat exposure as well (6). Heat effects on embryos and fetuses have been studied using rats, guinea-pigs, hamsters, and other smaller rodents. In all these species, at all stages, fetuses were at risk for developmental delays or defects depending on when heat was administered (6). A fMRI will not cause a pregnant woman's body temperature to raise as much as the rodents experienced in the studies and certainly not for so long.

Image courtesy of Flickr.

However, my concern isn’t that in one iteration the temperature will cause developmental damage to the fetus; my concern is what happens to a fetus developmentally after multiple exposures and an irregular amount of heat exposure over a long period of time. Due to fetuses being mobile subjects, multiple iterations of a fMRI session may be needed to capture a specific developmental period and to capture the brain at many different parts of the developmental time frame. With all the exposure to fMRI heat, sound, and the stress the mother may accrue, precautions should be in place to prevent overexposure to these risks. Additionally, the informed consent document for this research should mention that there may be potential long-term risks to participating that are currently unknown and thus possibly unaccounted for. 

While attending the 2017 International Neuroethics Society (INS) Annual Meeting, I was put in touch with a radiologist who suggested that to moderate the amount of heat energy the fetus and mother absorb during the fMRI trial, you must first note what type of pulse sequence is used. Pulse sequences in fMRI scans determine the contrast between different types of brain structures to provide better clarity, e.g. between grey and white matter (8). Furthermore, repeated and lengthy exposure to sounds above the threshold that fetuses hear has been linked to abnormal chromosomal development, hearing damage, and (as a result) poor sociability (7). The same radiologist offered his expertise here as well. He told me that modifying the pulse sequence modifies both sound and heat. As I mentioned in my first paragraph, my ethical analysis is still underway. Moving forward, I will be referring to experts in radiology on safe parameters and safety precautions. 

Stress that mothers experience over the course of a pregnancy may cause developmental problems, including, but not limited to, central nervous system damage (2). It’s possible that being involved in a longitudinal study may put extra stress on some, but certainly not all, pregnant women. Researchers should observe pregnant women closely for signs of stress and have follow-up interviews to watch for abnormal stress as well. I had the pleasure of speaking briefly with Dr. Thomason, one of the authors of the paper that sparked this journey, about her own test subjects. She claimed that her mothers did not feel abnormal stress throughout her fMRI studies. I think this is wonderful, but I would be remiss if I assumed this will always be the case. 

Moving forward, precautions need to be made to ensure that the well-being of the subjects is prioritized. Not only because this is the ethical path, but also because protecting the development of the fetus would also preserve the validity of the data collected. In addition, special attention should be paid to this research due to the insight it can provide regarding fetal brain structure and connectivity and even perhaps what qualifies as (morally relevant) sentience.

_______________

Molly is an undergraduate psychology major, in her third year, at George Mason University. Her minor is neuroscience and she has been interested in neuroethics research since her second year. She has been conducting psychology research in multiple labs on campus since right after her first year. She hopes to someday explore the ethical implications that come about from AI creation and wants to explore this question from the viewpoint of what consciousness is and if it is a relevant aspect of moral status.  









References

1. Heuvel, M. I. van den, & Thomason, M. E. (2016). Functional Connectivity of the Human Brain in Utero. Trends in Cognitive Sciences, 20(12), 931–939. https://doi.org/10.1016/j.tics.2016.10.001

2. Marques, A. H., Bjørke-Monsen, A.-L., Teixeira, A. L., & Silverman, M. N. (2015). Maternal stress, nutrition and physical activity: Impact on immune function, CNS development and psychopathology. Brain Research, 1617, 28–46. https://doi.org/10.1016/j.brainres.2014.10.051 

3. Buckner, Randy L., et al. “The Brain's Default Network.” Annals of the New York Academy of Sciences, vol. 1124, no. 1, Mar. 2008, pp. 1–38. NCBI, doi:10.1196/annals.1440.011. 

4. Uytun, M. C., Karakaya, E., Oztop, D. B., Gengec, S., Gumus, K., Ozmen, S., … Ozsoy, S. D. (2016). Default mode network activity and neuropsychological profile in male children and adolescents with attention deficit hyperactivity disorder and conduct disorder. APA PsycNET. https://doi.org/10.1007/s11682-016-9614-6 

5. Garrity AG, Pearlson GD, McKiernan K, Lloyd D, Kiehl KA, Calhoun VD. Aberrant “default mode” functional connectivity in schizophrenia. American journal of psychiatry. 2007 Mar;164(3):450-7. 

6. Edwards, M. J., Saunders, R. D., Shiota, K. (2003). Effects of heat on embryos and foetuses. International Journal of Hyperthermia, 19(3):295-324 

7. Krueger, C., Horesh, E., Crosland, B. A. (2012). Safe Sound Exposure In the Fetus and Preterm Infant. Journal of Obstretic, Gynecologic & Neonatal Nursing, 41(2):166-170 

“What Is FMRI?” What Is FMRI?, UC San Diego Center for Functional MRI, fmri.ucsd.edu/Research/whatisfmri.html. 

8. Asakura, Hirobumi. “Fetal and Neonatal Thermoregulation.” Journal of Nippon Medical School, vol. 71, no. 6, 2004, pp. 360–370. J-Stage, doi:10.1272/jnms.71.360. 

9. Sumner, W. I., & Feinberg, D. S. (1997). “A Third Way.” In The Problem of Abortion (3rd ed., pp. 98-117). Westminster Publishing Company. 

10. Savulescu, Julian. (2001) “Procreative Beneficence: Why We Should Select the Best Children.”Bioethics, vol. 15, no. 5-6, Oct. 2001, pp. 413–426. PubMed.gov, doi:10.1111/1467-8519.00251. 

11. Elizabeth Gedge, ‘‘Healthy’ Human Embryos and Symbolic Harm,’ In J. Nisker, F. Baylis, I. Karpin, C. McLeod, & R. Mykitiuk, eds. The ‘Healthy’ Embryo: Social, Biomedical, Legal and Philosophical Perspectives (Cambridge: Cambridge University Press, 2010). 

12. Cole, Michael W., and Walter Schneider. “The Cognitive Control Network: Integrated Cortical Regions with Dissociable Functions.” NeuroImage, vol. 37, no. 1, Apr. 2007, pp. 343–360.ScienceDirect.com, doi:10.1016/j.neuroimage.2007.03.071. 

13. Natoli, J. L., Ackerman, D. L., McDermott, S., & Edwards, J. G. (2012). “Prenatal diagnosis of Down syndrome: a systematic review of termination rates (1995-2011).” Prenatal Diagnosis, 32(2), 142–153. https://doi.org/10.1002/pd.2910

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Kluck, M. (2018). Ethical Implications of fMRI In Utero. The Neuroethics Blog. Retrieved on , from http://www.theneuroethicsblog.com/2018/05/ethical-implications-of-fmri-in-utero.html

The Brain In Context

By Sarah W. Denton

Sarah W. Denton is a research assistant with the Science and Technology Innovation Program at the Wilson Center. Denton is also a research assistant with the Institute for Philosophy and Public Policy at George Mason University. Her research primarily focuses on ethical and governance implications for emerging technologies such as artificial intelligence, neurotechnology, gene-editing technology, and pharmaceuticals. 

Tim Brown, University of Washington PhD student and research assistant with the Center for Sensorimotor Neural Engineering’s (CSNE) Neuroethics Thrust, introduced the session titled, “The Brain in Context,” at the International Neuroethics Society’s 2017 Annual Meeting moderated by Husseini Manji, Janssen Global Therapeutic Neuroscience Area Head. This session provided a multidisciplinary view of the challenges we face today in understanding the context of lived experiences and how our brains impact our environments. Getting at the heart of the context in which our brains develop and grow may help us to reduce stigma by increasing our understanding of how our environments impact our brains in a myriad of ways.

Socioeconomic Status and the Brain

Martha Farah, Director of the Center for Neuroscience & Society at the University of Pennsylvania, kicked off the panel discussion by speaking about her recent research on the relationship between socioeconomic status (SES) and the brain. The factors affecting the brain not only arise from our physical bodies, but also include our social environments [1]. Specifically, Farah has focused her attention on socioeconomic status and how it affects everything, from life expectancy to education to income – all of which are inherently connected to the context and the environments in which our brains develop.

The way the brain develops is a causal pathway to a variety of outcomes. For instance, there is a surprisingly strong relationship between cognitive ability, as measured by IQ and school achievement, and SES [2]. Farah’s lab performed three studies that aimed to characterize SES disparities in terms of cognitive neuroscience’s model of mind, rather than through intelligence and standardized test scores [3,4,5]. Cognitive neuroscientists employ the ‘information processing’ view of the mind, which is a fundamental construct of cognitive psychology that “refers to the rule-governed transformation of [both unconscious and conscious] metal representations” (e.g., explicit perception, implicit learning, implicit memory [6]. This view of the mind appeals to computational methods in both cognitive psychology and neuroscience to understand the molecular mechanisms implicated in information processing [7].

Developed from a slide shown during Farah’s panel 

discussion titled, “Socioeconomic Status and the Brain,” 

at the 2017 International Neuroethics Society Annual Meeting 

on November 10, 2017 at the American Academy for the 

Advancement of Science (AAAS) building in Washington, D.C.

Farah’s findings suggest that the most pronounced socioeconomic-derived disparities were both executive function associated with the prefrontal cortex and declarative memory associated with the hippocampus. We know that the brain is usually discussed in a descriptive and mechanistic way, but this conception may be unhelpful. Although there are currently no unique implications, research moving towards a more illustrative and actionable understanding of the brain in context is adding to the weight of evidence that our environment, including SES, has profound affects on our brains. Thus, neuroethics and neuroscience policy is relevant precisely because it increases the weight of evidence. The end goal of Farah’s research program is to understand poverty using insight from neuroscience in order to help “break the cycle” and guide future policy decisions. 

Prenatal Programming of Human Fetal Brain Development 

The second panelist, Moriah Thomason, Director of the Perinatal Neural Connectivity Unit of the Perinatology Research Branch with the Detroit Medical Center and Wayne State University School of Medicine, built upon this discussion and defined the first context of our brain – the womb. Her research centers around prenatal programming of human fetal brain development and has found that alterations in brain development in utero have significant cognitive effects.

Earlier this year, Thomason published a study in Scientific Reports that suggested differences in how certain brain regions communicate with each other in fetuses that were later born prematurely when compared to fetuses that were carried to term [8].

Thomason’s research team used fMRI to determine which brain regions were involved in synchronized activity between brain regions, which suggests that these regions are well connected and share information [9]. The brain in utero is essentially in a state of becoming and sets the stage for our future abilities even before we take our first breaths outside of the womb. For instance, a mother experiencing high levels of stress seems to imprint this stress on the fetal brain [10]. This fetal programming affects the functional connectivity in the fetal brain prior to birth. Her “Prenatal Imaging of Neural Connectivity (PINC)” study has found that the prenatal stress score (depression, perceived stress, satisfaction with life, and anxiety) is correlated to fetal brain connectivity in several notable brain areas, including three subregions of the cerebellum.

Image courtesy of Pexels.

One implication of Thomason’s research is that we no longer need to limit the brain to a postnatal context– neural connectivity begins prior to birth. This suggests that prenatal brain development is intimately tied to the mother’s environment and psycho-physio state, which may have a wide range of implications that have yet to be explored. This is just the beginning for Thomason and prenatal neuro-connectivity research, and I am eager to see neuroethicists explore the implications of the brain in the context of the womb.

Do Brains Matter Using Screens?

The final panelist, Hervé Chneiweiss, Research Director at École des Neurosciences Paris Île-de-France, moved us from the brain in the context of the womb to the brain in the context of our increasing use of technology – particularly screens like those found in our phones, televisions, and tablets. The social context is perhaps the most important while we learn; yet, our increasing reliance on screens as an educational tool may hinder our ability to learn how to interact with others in our physical environments [See 11,12,13].

In this context, neuro-education has evolved from two-dimensional to five-dimensional; but now we are moving back to 2D screens. Moreover, there is a correlation between excessive screen time and the development of psychiatric disorders, lack of sleep, and impaired cognition [14]. Beyond the potential cognitive effects of excessive screen-time, Chneiweiss is also concerned about the marketing of attention, i.e., the subjection to excessive screen time in the workplace and nonmaleficence in advertising the educational benefits of brain training apps.

On the latter, Chneiweiss is particularly concerned about the vague educational benefit claims made by many apps directed at vulnerable populations like children and seniors [15]. The democratization of screens has created two new kinds of pathology: nomophobia, phobia of being without a phone; and fomo, the fear of missing out, fear of being disconnected of the social network. While these characterizations are a bit tongue-in-cheek, they highlight real problems that can significantly affect our cognitive abilities.

Image courtesy of Pixabay.

As a general rule of thumb, owning a console or tablet presents more risks than benefits, such as insomnia and social-skill development, for children under the age of six [16]. But, by the time they reach their teenage years, certain action-oriented games can indeed improve cognitive abilities such as visual attention and decision-making [17]. To address this discrepancy, we must educate children and their parents on how their brains work and how screens affect their brain functions.

Conclusion



All three panelists presented neuroscience research in the social context. Martha Farah’s presentation showed how social and other environmental factors, like income, can have significant effects on brain development. Moriah Thomason’s presentation of her research went even farther – connecting stress levels of mothers to prenatal brain development. Finally, Hervé Chneiweiss spoke on how the use of screens, like those found in television sets and iPhones, can not only affect child and adolescent brain development but can also affect how they interact in the social environments around them.
The primary takeaway from this session is that our brains do not develop in a neuropsychiatric vacuum– our social and cultural environments can have significant implications for neuroscience. In the Q&A after the presentations, I found it of particular interest that each panelist agreed that the social context is the most important context when it comes to understanding the brain and conducting neuroscientific research.

Now, as we move forward, we should approach neuroscience research and its findings in the context of our social environments if we are to create a more holistic understanding of the brain.

References

[1] M. Farah. 2012. “Neuroethics: The Ethical, Legal, and Societal Impact of Neuroscience,” The Annual Review of Psychology: University of Pennsylvania, 63: pp. 571-91 [https://neuroethics.upenn.edu/wp-content/uploads/2015/06/farah-Neuroethics-The-Ethical-Legal-and-Societal-Impact-of-Neuroscience.pdf ]; B. Avants, et al. 2012. “Early childhood environment predicts frontal and temporal cortical thickness in the young adult brain,” presentation at The Society for Neuroscience 2012 Meeting, abstract can be found here: [http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=734b1ccd-cfcf-4394-a945-083ca58f8033&cKey=7b3e8587-f590-4d94-ae3f-e050d52e8488&mKey=%7b70007181-01C9-4DE9-A0A2-EEBFA14CD9F1%7d]; M. Mariani. 2017. “The neuroscience of inequality: does poverty show up in children’s brains?” The Guardian, (13 July) [https://www.theguardian.com/inequality/2017/jul/13/neuroscience-inequality-does-poverty-show-up-in-childrens-brains].

[2] Martha Farah, Socioeconomic Status and Brain. University of Pennsylvania, Center for Neuroscience & Society. [https://neuroethics.upenn.edu/martha-j-farah-phd/research/socioeconomic-status-and-brain/].

[3] K. Nobel, M.F. Norman, and M. Farah. 2005. “Neurocognitive correlates of socioeconomic status in kindergarten children,” Developmental Science, 8(1): pp. 74-87. [https://neuroethics.upenn.edu/wp-content/uploads/2015/06/Development-kindergarten.pdf].

[4] M. Farah, et. al. 2006. “Childhood poverty: Specific associations with neurocognitive development,” Brain Research, 1110: pp. 166-174. [https://neuroethics.upenn.edu/wp-content/uploads/2015/06/Development-povertyassociation.pdf ].

[5] K. Noble, B. McCandliss, and M. Farah. 2007. “Socioeconomic gradients predict individual differences in neurocognitive abilities,” Developmental Science, 10(4): pp. 464-480. [https://neuroethics.upenn.edu/wp-content/uploads/2015/06/Development-gradiants.pdf]

[6] D. David, M. Miclea, and A. Opre 2004. “The Information-Processing Approach to the Human Mind: Basics and Beyond,” Journal of Clinical Psychology, 60(4): pp. 355,357. [https://www.ncbi.nlm.nih.gov/pubmed/15022267].

[7] "The Philosophy of Neuroscience" The Stanford Encyclopedia of Philosophy, Chapter 6: A Result of the Co-Evolutionary Research Ideology - Cognitive and Computational Neuroscience. 2010. [https://plato.stanford.edu/entries/neuroscience/#ResCoEvoResIdeCogComNeu].

[8] M. Thomason et. al. 2017. “Weak functional connectivity in the human fetal brain prior to preterm birth,” Scientific Reports, 7(39286). [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5221666/]. Of course, these findings are preliminary, but Thomason is enthusiastic and plans to continue this research with larger sample sizes.

[9] G. Miller. 2017. “Pioneering study images in fetal brains,” Science Magazine, (9 January). [http://www.sciencemag.org/news/2017/01/pioneering-study-images-activity-fetal-brains].

[10] M. Thomason et. al. 2017. “Weak functional connectivity in the human fetal brain prior to preterm birth,” Scientific Reports, 7(39286). [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5221666/].

[11] J.E. Brody. 2015. “Screen Addiction is Taking a Toll on Children,” The New York Times (6 July) [https://well.blogs.nytimes.com/2015/07/06/screen-addiction-is-taking-a-toll-on-children/]

[12] USC Center for Work and Family Life, “Sleep Deprivation in the Age of Electronics,” [http://cwfl.usc.edu/wellness/sleephandouts/Sleep_Deprivation_in_the_Age_of_Electronics-CWFL.pdf]

[13] G.S. Goldfield, et al., “Screen time is associated with depressive symptomatology among obese adolescents: a HEARTY study,” European Journal of Pediatrics, v. 175(7): pp. 909-919 (July) [https://link.springer.com/article/10.1007/s00431-016-2720-z].

[14] P. Reany. 2011. “Not Getting Enough Sleep? Turn off the Technology,” Reuters (7 March) [https://www.reuters.com/article/us-sleep-technology/not-getting-enough-sleep-turn-off-the-technology-idUSTRE7260RH20110307].

[15] R. Robbins. 2016. “U.S. Cracking Down on ‘Brain Training’ Games,” Scientific American, STAT (6 September) [https://www.scientificamerican.com/article/u-s-cracking-down-on-brain-training-games/]; E. Yong. 2016. “The Weak Evidence Behind Brain-Training Games,” The Atlantic (3 October) [https://www.theatlantic.com/science/archive/2016/10/the-weak-evidence-behind-brain-training-games/502559/].

[16] K. Subrahmanyam, et al. 2000. “The Impact of Home Computer Use on Children’s Activities and Development,” The Future of Children, (Fall/Winter): Princeton University [https://www.princeton.edu/futureofchildren/publications/docs/10_02_05.pdf].

[17] I. Granic, et al. 2014. “The Benefits of Playing Video Games,” American Psychologist, (January) [https://www.apa.org/pubs/journals/releases/amp-a0034857.pdf]; D. Bavelier, et al. 2011. “Brains on video games,” Nature Reviews Neuroscience, 12: pp. 763-768 (18 November) [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4633025/]. 

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Denton, S. (2018). The Brain In Context. The Neuroethics Blog. Retrieved on , from http://www.theneuroethicsblog.com/2018/03/the-brain-in-context.html

Overexposed: The role of environmental toxicants on your brain

By Carlie Hoffman

It
is often said that we are products of our environment: who we are is
shaped by the things, people, and situations with which we surround
ourselves. However, whatever we may like to think, we are not in
control of every facet of our environment. In fact, we are unknowingly
and involuntarily exposed to dozens of man-made environmental chemicals,
called toxicants,
each day that can negatively alter our bodies and even our very brain
matter. In essence, we are becoming literal products of our environment.

Synthetic
chemicals and toxicants are ubiquitous within our surroundings. While some toxicants come from obvious
sources, like cigarette smoke and car exhaust, other sources of exposure
are more subtle. For instance, electrical equipment (like computers
and cell phones), beauty products (like makeup and shampoo), mattresses,
and furniture all contain flame retardants, chemicals used to reduce flammability [3, 13]. Bisphenol A (BPA) and phthalates,
chemicals used to harden plastics, can also be found in dental
sealants, cigarette filters, soda bottles, and the linings of canned
foods [4, 8, 12]. Additionally, dichlorodiphenyltrichloroethane (DDT),
a pesticide commonly used in the mid-1900s to combat outbreaks of
pests, malaria, and lice, was banned in 1972 in the US and yet is still currently present within both the environment and human tissues [12].

Pesticides not only harm insects, but certain doses can also have harmful effects on the human body.

The presence of chemicals within almost every facet of our society means we are
subjected to varying levels of environmental exposure throughout our lives– from the womb to the grave. A growing desire to
characterize the effects of this lifetime of exposure resulted in the
creation of a new concept: the “exposome.”
Defined in 2005 by Dr. Christopher Wild as “every exposure to which an
individual is subjected from conception to death,” this definition was
expanded by Dr. Gary Miller and Dr. Dean Jones
in 2014 to be “the cumulative measure of environmental influences and
associated biological responses throughout the lifespan, including
exposures from the environment, diet, behavior, and endogenous
processes” [9, 14, 15]. Indeed, some say the exposome profile may
tell a narrative about our individual lives with astounding accuracy–
including where we’ve traveled, what we’ve eaten, and trends in our
overall behavior.

As Dr. Wild stated, our environmental exposures, and our lives, begin in the womb. After this point, the developing fetus is subject to many
of the environmental chemicals and toxicants to which the mother is
(knowingly or unknowingly) exposed. A study described by CNN illustrated this point and found that pregnant mothers were exposed to pesticides and air
pollutants while engaging in everyday activities.  Some of these chemicals were also able to pass through the umbilical cord and enter into the bloodstream of the fetus, resulting in an average of 232 chemicals being found in the cord blood of 10 babies born over the course of the study.  Pregnant mothers were also exposed
to chemicals from unexpected sources, like taking a shower, cleaning the
house, and putting on makeup.  Some of these chemicals also made it into the fetus and were found in the fetal cord blood.  However, it
is important to note that the mere presence of such chemicals within the
blood is not necessarily harmful to human health. Instead, toxicity is
dependent upon the concentration and duration of exposure a person, or
fetus, is subjected to– meaning the presence of exposure does not always lead to the occurrence of detrimental health effects.



That
being said, certain types of environmental exposure can result in
numerous negative consequences for the brain. For instance, exposure to certain
amounts of air pollutants and pesticides during development has been associated with a
reduction in white matter volume in the brain, slower information
processing speed, behavioral problems, attention deficit/hyperactivity
disorder (ADHD) symptoms, and an alteration in mental and psychomotor
development [7, 10]. One study retrospectively examined a group of
adults in Cape Cod, Massachusetts who experienced prenatal and early
childhood exposure to drinking water contaminated with
tetrachloroethylene, a chemical solvent used in dry cleaning, and found
that early exposure was associated with impaired vision, increased
reports of impulsive behavior, and increased risks of developing bipolar
disorder and post-traumatic stress disorder (PTSD) in adulthood [1, 2,
6]. In addition, excessive prenatal exposure to BPA and phthalates has
been found to alter sexually dimorphic development of the brain and can also lead to alterations in anxiety, hyperactivity, and emotional control [4, 8, 12].  Thus, exposure to environmental chemicals can influence how our brains function, affect our mental health, and alter how we interact with the world around us.

Given
these documented detrimental health effects, we should seek to avoid
excessive environmental exposures. However, while we can limit our
interaction with known sources of environmental
chemicals, such as by avoiding areas that have recently been sprayed
with pesticides or not living in areas subjected to large amounts of car
exhaust, how do we protect ourselves from environmental toxicants coming from largely unknown and unavoidable sources?  And why are chemicals are being added to
commonly-used household items in the first place when such substances
have the potential to negatively alter our brains and neurodevelopment?

The
answer to this latter question can be traced to the years surrounding
the Great Depression and World War II. In this era, the fields of human
industry and farming began to employ synthetic chemicals for numerous
beneficial purposes, like controlling pest populations, reducing
flammability, and acting as additives in paints and wood finishes. These
potential useful applications led to the quick introduction of such
compounds to widespread use without thorough examination of their
possible negative impacts on human health. The reason for rapidly adding
these chemicals was described in the 1930s by the president of
the Halowax Corporation: “The problem so far as the chemical
manufacturer is concerned is a question of timing… should we take a
product of which you have developed, say, 5 or 10g and spend $50,000 on
research to determine whether or not it is toxic, or should you wait
until you have determined whether you have a market for it?...You can
see that would run into box car numbers in the way of dollars and cents
until you ever sold any” [12]. Essentially, adequate chemical testing
was not performed because it was not cost-effective, resulting in the
public remaining largely unaware of the adverse health effects that could arise from excessive exposure to these added chemicals.

Unfortunately, this cost-driven lack of investigation still describes how chemical research is performed today.  An article in The New England Journal of Medicine
stated that only 200 of the 80,000 chemicals added to products sold
within the US in 2011 were sufficiently tested for carcinogenicity, not to mention the number of chemicals that were inadequately tested for other, non-cancer-related negative outcomes arising from excessive exposure [5].

EPA

This mass-production of chemicals without adequate toxicity testing continues in part because of the vague chemical testing regulations that govern chemical companies in the United States. According to
the Environmental Protection Agency’s (EPA) chemical testing policy,
chemical companies are responsible for determining whether their
substances “may present an unreasonable risk of injury to health or the
environment.” The nebulous wording of this regulation, the lack of a
precise definition of “unreasonable risk,” and the increased cost
associated with increased research has resulted in many chemical
companies simply testing their chemicals for acute toxicity (which
involves giving experimental animals large doses of a chemical and
checking for a decrease in lifespan or the presence of illness), instead
of performing long-term testing (which involves giving experimental
animals small doses of a chemical over a long period of time). Thus,
the effects of gradual exposure, as would be experienced through daily
contact with a chemical over the course of a lifetime, are not examined
and the effects of such gradual exposure are only determined as people
are exposed to these chemicals for many years.

Thankfully,
this problem of non-consensual daily exposure to toxic chemicals is not
one without a solution– though working toward this solution will not be
easy. One of the first steps toward a less-polluted and more hospitable future is to
continue characterizing the human exposome. Several organizations
within the United States and Europe, including the HERCULES
exposome research center at Emory University, operate under this goal.
These organizations seek to develop a better understanding of the role
of the environment on brain disease onset and progression, to discover
chemicals that cause disease, and to remove or diminish exposures to
such chemicals [11]. More stringent regulations on chemical testing and
increased collaboration between chemical companies and neuroscientists
will also move chemical testing in the right direction, helping to
elucidate the long-term effects of environmental chemicals on the brain
and leading to more detailed chemical toxicity characterization.
Unfortunately, increased chemical testing is often viewed as an
unnecessary hindrance and is perceived as being less cost-effective than
rapidly mass-producing a chemical. However, more thorough testing and
increased chemical regulation will result in an improved quality of
life, better brain development, and an increase in human liberties for
individuals throughout our society and the world– and that is priceless.

Works Cited



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Hoffman, C. (2015). Overexposed: The role of environmental toxicants on your brain. The Neuroethics Blog. Retrieved on , from http://www.theneuroethicsblog.com/2015/09/overexposed-role-of-environmental.html