Plastic production suffered a great increase since it started to be commercialised 70 years ago. In the beginning, the overall production reached about 0.5 million tons per year. However, in 2017, it increased up to 348 million tons. Along with plastic production, one big concern has arisen: environmental pollution.
Anthropogenic plastic pollution is a major problem worldwide as plastics accumulate at an alarming rate. People started to notice plastic accumulation not only in terrestrial but also in marine environments. Even though specific laws and regulations were made to tackle this problem, scientists still find large quantities of microplastics (MPs) that are hazardous to the environment and human health.
What Are Microplastics And Where Do They Come From?
Microplastics (MPs) are plastic debris with less than 0.5 cm of size. They are generally classified according to their sources. Primary MPs, for example, come from MPs-containing products, as is the case of microbeads in our toothpaste and other cosmetics. On the other hand, secondary MPs result from the degradation of larger plastics. Plastic suffers a slow degradation through photo, oxidative and hydrolytic processes, thus breaking down and originating the smaller pieces known as MPs.
Due to their low density, they are usually found floating in the marine environment. Up to the moment, they have been found in the open ocean, as well as in enclosed or semi-enclosed seas. Even in more remote areas, such as the Arctic, Antarctica, and deep-sea sediments, MPs are present. Polyethylene (PE), polypropylene (PP), and polystyrene (PS) are among the most frequent sampled MPs.
Rivers are important reservoirs for plastics that will further enter the oceans. A study indicated that 1.15 to 2.41 million tons of plastic float from the rivers to the oceans per year. Poor waste management is often the main cause for this.
What Are The Consequences Of MPs To The Marine Environment?
Because of their small size, MPs are easily ingested by marine organisms, including lugworms, mussels, amphipods, barnacles, sea cucumbers, and fish. Besides, some microplastic shape and size resemble prey that fish feed on. Once MPs are ingested, they can be either excreted or retained in the tissues, especially in the gastrointestinal tract. They have also been found in the stomach, oral and ventilation areas of some marine organisms. In case of retention, trophic transfer and accumulation in the food chain may occur.
One should also consider the fact that plastics are frequently manufactured with other substances in its composition that might be hazardous. The concern increases due to the fact that MPs may function as vehicles for the transport of toxic metals, persistent organic pollutants (POPs), or dangerous microorganisms that possibly will be transferred to organisms.
The ingestion of MPs by marine organisms can block their digestive system, thus decreasing feeding activity. Studies have shown that MPs have carcinogenic and endocrine-disrupting effects. Besides, it decreases fish populations and richness of species, and also affects the growth and reproduction of some animals. Eggs, embryos, and larvae, as well as filter feeders, are considered more susceptible to MPs.
What Risks Do MPs Represent To Human Health?
Humans can be exposed to MPs directly through the environment. Nevertheless, the main route of exposure is by ingestion of food items, such as fish, sugar, table salt, bottled water, among others. MPs can also be inhaled, and it has been found in cancer biopsies. However, it hasn’t been proved a connection between these two events. Dermal contact is less frequent.
Exposure to MPs can cause chronic inflammatory lesions. Studies showed that, among other consequences, they can cause disruption of cellular processes and tissues, and dermatitis. In addition, they can disturb energy and lipid metabolism, and cause oxidative stress. In vivo studies showed that MPs may be associated with the increased incidence of some immune and neurodegenerative diseases. Besides, it is suggested that microplastic internalization by cells may occur, thus interfering with important intercellular structures.
Moreover, MPs can suffer translocation to distant tissues, especially during an inflammation process. When in circulation, they might cause pulmonary hypertension, vascular occlusions, increased coagulability as well as cytotoxicity. In addition, MPs can potentially cause asthma, cardiovascular disease, dyspnea or respiratory irritation.
What Measures Are Being Implemented To Tackle Microplastic Pollution?
One of the United Nations Development Goals is to “Ensure access to water and sanitation for all”. To achieve this, among other targets, they aim to reduce water pollution and eliminate the release of hazardous materials and chemicals to water.
In fact, several regions have created regulations in order to reduce the production of primary microplastics as well as single-use plastics. For instance, the Netherlands, Ontario (Canada), France and the United States of America banned or declared their intent to control the use of microbeads that are frequently present in cosmetic products. Nevertheless, secondary MPs are a major source of environmental pollution and more regulation is needed.
Additionally, the Group of 7 (G7) including Canada, France, the United Kingdom, USA, Japan, Italy, and Germany work hard to develop an action plan to reduce marine litter and waste produced by land- and sea-based activities.