Microplastics, environment and child health

Abstract

The substantial increase in scientific studies [1] in recent years has clarified and evidenced that the use of plastic material, widely employed in daily life due to the advantages it offers with respect to other materials, can cause environmental damage. In particular, several studies have focused on microplastics (MPs), defined on the basis of a size smaller than 5 mm. MPs are subdivided into two groups [2]: primary MPs, used both industrially as plastic pellets and in personal care products (i.e. toothpastes, nail polishes, sun creams, scrubs, bath gels) [3] and secondary MPs, derived from the plastic waste dispersed into the environment which undergoes progressive degradation because of photo and thermooxidative processes and mechanical abrasion [4]. These latter derive mainly from industrial packaging and textile fibers released into the washing water from machinewashed clothing [2]. Overall, it is estimated that between 75,000 and 300,000 t of microplastics are released into the environment each year in the EU alone [5]. It must also be borne in mind that MPs can release complex mixtures of chemicals into the environment as many types of additives are used in the industrial production of plastics to provide specific features (for example flame retardants, UV stabilizers, heat stabilizers, and plasticizers) [6]. Moreover, due to their hydrophobic surface, MPs can adsorb and concentrate to a high degree hydrophobic organic contaminants (HOCs) such as polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides and polychlorinated biphenyls (PCBs) [7]. They also accumulate heavy metals such as cadmium, zinc, nickel, and lead [8]. Several studies have shown the presence of MPs in marine waters [9], in terrestrial soil [10], in the air [11] and in tap water [12] in highly populated areas as in regions far from inhabited centers [13]. In other words, MPs are so ubiquitous [14] that scientists have suggested that they will represent an index of the geological era we are experiencing that some geologists define as anthropocene [15]. In addition, various researches have recently shown that MPs can be introduced into the human body, and are found in human organs and tissues [16]. Most commonly MPs are introduced into the body orally, and have been detected in several foods. Most studies have focused on foods of marine origin including invertebrates, crustaceans, and fish [17, 18] but MPs have been found also in sea salt coming from different countries [19], primarily fragments but also filaments and films. Moreover, polyethersulfone and polysulfone have been reported as common types of MPs detected in branded milk samples [20] and have been found in bottled water, honey, beer, plastic teabags and soft drinks in addition [21–23] as well as in fruit and vegetables (particularly in apples and carrots) [24]. Moreover, MPs have been identified in the feces of human volunteers [25]. Based on the consumption of foodstuff, bottled water and on inhalation it has been estimated that a person’s yearly intake in the USA is within a range from 39000 to 121000 particles of MPs [26]. The second mode of introduction of the MPs into the body is through inhalation. Using a Breathing Thermal manikin, Vianello et al. [27] concluded that MPs represent a non-negligible fraction of indoor airborne particulate, which can be both inhaled and ingested. Finally, the possibility of skin absorption should be considered even if there is no definitive evidence to prove this. Further experiences/studies on this aspect would be useful and are warranted [28]. At this stage the logical and fundamental question is: “what are the real risks of disease for humans having ascertained the presence of MPs within the body?” Based on current knowledge this question remains unanswered. However, although currently we are unable to give an exact answer, one must take into consideration the wide range of results obtained from studies in vitro