Daily exposure of chemical substances

Today, there are over 50 million types of chemical substances, with new ones being added to the list on a daily basis. Here, I would like to look at the chemical substances that make up familiar, everyday products and discuss the impact they have on us as well as on our environment. Most of the chemical substances that we use to make our lives comfortable and convenient are artificially synthesized. Generally speaking, most chemicals will break down as they pass through atmospheric, soil, aquatic, biological, or other environmental systems, but the refractory properties of certain chemicals make them resistant to breaking down in this way. These substances are making their first appearance on the planet in its 4.6 billion years of history, and have no decomposers on earth, which decompose at an extremely slow pace. Many of these chemically stable substances are extremely useful in industrial contexts—meaning that the impact they have on the environment once they are produced and used in massive quantities is far from insignificant. Polychlorinated biphenyls (PCBs) and dichloro-diphenyl-trichloroethane (DDT) are just two examples of refractory chemical substances that are making headlines as so-called residual organic pollutants. Fluorocarbons (Freon), said to destroy the ozone layer, is an example of a refractory gas that does not easily break down in the environment either. Freon was originally developed to replace ammonia as a refrigerant in household refrigerators. It is extremely stable chemically and resistant to heat, and was therefore widely used in air conditioners and refrigerators as a refrigerant as well as an aerosol propellant and solvent. Unfortunately, we now know that when waste Freon is released into the atmosphere, it goes into the stratosphere and destroys the ozone layer—so the gas has been subject to a blanket ban since January 1996^[1]. The history of Freon illustrates a characteristic of ecological problems, which is that we finally identify their causes only after we have put huge amounts of the offending substance into the environment and witnessed its significant negative impacts.

Light, durable, convenient plastic products

Plastics have come into the spotlight in recent years as a substance driving environmental pollution. One of the most familiar examples is the ubiquitous plastic shopping bag. These bags are light, durable, and water resistant; take up very little space when folded up; and can be dyed to create colorful patterns or fashioned into custom designs. They are also cheap. When you really think about it, plastic bags are really in a class of their own when it comes to convenience. Light, strong, convenient plastic products are everywhere in our daily lives—from toys to everyday necessities. However, the plastics used to make these products are almost all refractory substances. Biodegradable plastics do exist, but they have only found limited application, since they still have not been able to surpass our existing products in terms of performance and cost. As the developing countries of the world experience economic growth, we are seeing the use of non-biodegradable plastics skyrocket, with the result that plastic garbage is rapidly piling up all over the world.

The scattering of micro-sized plastics

The substances that we emit into the environment eventually flow into our oceans, and the same is true of the plastics that we fail to recover and recycle. It has actually been reported that more than 70% of the waste in our oceans is plastic^[2]. When plastic enters the ocean, it tends to drift along the surface for a while, gradually becoming smaller over time as it is exposed to physical and chemical stimuli (including sunlight and wave action). Pieces of plastic that have been reduced to 5 mm in size or less are called microplastics, but some become so tiny that they cannot be seen by the naked eye. At this point they are indistinguishable from living plankton, and zooplankton may even ingest them^[3]. Microplastics are now found floating throughout the world’s oceans, and they eventually settle to the seafloor—since drifting microplastics form a biofilm of microorganisms that makes them heavier and heavier until they sink^[4]. Biofilms are masses of bacteria, much like the gooey layer that forms in a kitchen drain after some time. In this way, our plastic trash is becoming micro-sized and invisible, drifting throughout the world’s oceans, settling into the deep sea, and then scattering across every possible coastline in beach sand and debris.

Carriers of microplastics

Today, we are finding plastic in the stomachs of almost every sea creature, from pelagic seabirds to deep-sea organisms. As plastic pollution spreads, it starts travelling farther and farther up the food chain, eventually reaching the animals at the top. Microplastics have now been detected in more than 90% of northern fulmar seabirds in Hokkaido^[5][6], and a new danger associated with them is now becoming clear after further detailed study. While these microplastics are drifting throughout the environment, they are also absorbing and concentrating residual organic pollutants like PCBs and DDT. One report stated that these chemical substances could eventually reach a million times their environmental concentrations^[3]. What started out as simple plastic garbage has now taken a long journey and ended up as a microplastic housing concentrated toxic chemical substance—and sadly, it then gets inside animals as well. These chemicals have now been detected in the abdominal adipose tissue of seabirds that have ingested microplastics and shown to be traveling throughout their bodies^[7]. All of you reading this are smart enough to know what is coming next… microplastics have apparently been found in the oysters and shellfish we love to eat as well. A study on umbilical cords of Japanese babies in the womb showed the presence of PCBs (0.107 ± 0.040 ng/g wet weight), DDT (0.006 ± 0.002 ng/g wet weight), Bisphenol A, known as the environmental hormone (4.425 ± 5.037 ng/g wet weight), heavy metals, and more^[8]. Not all of these substances become plastic waste, but they do tell us that we are being exposed to toxic chemicals in our mother’s womb before we are even born.

Avoid or reuse plastic shopping bags

It has been said that in the next ten years, the amount of microplastics we release into the environment has the potential to increase threefold. Even if they are not currently at a level that is harmful to human health, history has already taught us what will happen if we keep tossing out plastic garbage at the current rate. Meanwhile, the basic way of how to reduce garbage is following the 3R method—reduce, reuse, and recycle. Japan is said to collect 80% of its plastic bottles, making it a world leader in that regard. Of course, it’s important to aim for a 100% collection rate, but it would be extremely difficult to get it higher than it is now. Recycling saves energy, but of course the most effective method is to reduce our consumption in the first place. My request to the readers is whenever possible, reduce garbage by refusing to use plastic bags, and if you do take them, make sure to reuse them at least twice before throwing them away. Environmental problems will improve when we all chip in and do our part however small. Just that tiny action of vowing to not use plastic bags any more than necessary may just save us—and save future generations as well.

Works Cited

1. ^ “Protect the Ozone Layer and Prevent Global Warming. Ministry of Economy,” Trade and Industry. 2005
2. ^ OSPAR Pilot Project on Monitoring Marine Beach Litter.Monitoring of marine litter in the OSPAR region
3. ^ Microplastics in marine environments: Occurrence, distribution and effects. Nerland, Inger Lise et al., Research report NIVA-rapport 6754. 2014
4. ^ Plastic Accumulation in the North Atlantic Subtropical Gyre. Kara Lavender Law et al., Science 329, 1185-88. 2010.
5. ^ Monitoring plastic ingestion by the northern fulmar Fulmarus glacialis in the North Sea. van Franeker JA et al. Environ Pollut. 159, 2609-15. 2011.
6. ^ Northern fulmars as biological monitors of trends of plastic pollution in the eastern North Pacific. Avery-Gomm S et al., Mar Pollut Bull. 64, 1776-81. 2012.
7. ^ Physical and chemical effects of ingested plastic debris on short-tailed shearwaters, Puffinus tenuirostris, in the North Pacific Ocean. Yamashita, R et al., Mar. Pollut. Bull. 62, 2845–2849. 2011.
8. ^ Necessity to establish new risk assessment and risk communication for human fetal exposure to multiple endocrine disruptors in Japan. Tokada et al., Congenital anomalies 42, 87-93. 2002.

Kahoko Nishikawa
Professor, Faculty of Commerce, Chuo University
Areas of Specialization: Microbial ecosystems and aquatic environments

Kahoko Nishikawa was born in 1966 in Yamagata Prefecture. In 1989, she graduated with a Bachelor of Agriculture from the Faculty of Applied Biological Science, Hiroshima University, going on to complete her master’s degree in The Graduate School of Home Economics, Ochanomizu University with a concentration in Food Sciences and Environmental micorobiology in 1991. In 2002, she completed the doctoral program (Doctor of Science) in Human-Environmental Studies in the Graduate School of Humanities and Sciences, Ochanomizu University. She took a position as a visiting research assistant studying microbe proteomics in the Department of Biochemistry, Cambridge University in July of 2006, going on to work as a specialized assistant in the Graduate School of Humanities and Sciences, Ochanomizu University and as an assistant instructor and then full-time lecturer in the Department of Traumatology and Critical Care medicine, National Defense Medical college Hospital before taking up her current position in 2015. Professor Nishikawa concurrently works as Guest Researcher, National Institute of Health Sciences. Her current research topics are the impact assessment of environmental chemical pollutants on aquatic ecosystems and the evaluation of techniques for mitigating environmental costs.