To the best of our knowledge, this is the first study investigating colored plastic food utensils as a potential source of Cd and Pb exposure in children, with no other studies of these plastic materials available in the literature. In the present study, the results showed that high concentrations of these metals determined by XRF had major potential for specific migration into simulant solutions and commercial beverages. Similar studies have been conducted involving plastic packaging for storing foods. Kiyataka et al. (2014) detected Pb levels of 30-40 mg.kg−1 using specific migrations tests, whereas cadmium concentrations proved below the limit of detection for the method.
Of the 674 items analyzed in the present study, 287 contained detectable concentrations of the metals (Table 1) and, of this total, 87 had levels which exceeded permitted limits. It is important to emphasize, however, that while levels in some items tested were within allowed limits, this does not rule out the possibility of samples containing some degree of contamination by Cd, Pb or other PTE not measured in this study.
The XRF results (Tables 1-4) were cause for concern, revealing mean Cd and Pb concentrations far exceeding limits allowed by U.S. and Brazilian law (Brazil 2008; US 1997; WHO 2010). A number of studies have been carried out on plastic toys as a source of exposure. Greenway and Gerstenberger (2010) evaluated lead contamination using XRF in toys from 50 day care centers in the USA. Results showed around 5.4% contained concentrations that exceeded legally allowed limits, with yellow items exhibiting the highest lead levels. The present study found the highest Cd concentration in green items (Table 3) and the highest Pb levels in orange and yellow utensils (Table 2). According to the National Institution of Metrology, Quality and Technology (INMETRO 2015), inorganic lead-based pigment can be used to confer paints yellow, orange and red hues. These pigments represent a low-cost option compared to other types of pigmentation, perhaps explaining the high concentrations of these metals in colored utensils.
Although the highest percentage of utensils exceeding the legal limit for lead (22.8%) were found in the district of Pari, the highest mean Pb concentrations were found in the city of Osasco, where both these regions had similar socioeconomic characteristics according to their IPVS. The ANOVA results showed a statistically significant difference between Groups 2 and 3 (p = 0.006). This finding was expected, given that mean Pb values for the Group 2 regions of Osasco and Pari were 4 times higher than those detected in the Group 3 districts of São Miguel and Capão Redondo (Group 3), despite the higher IPVS of the latter. Other factors to take into account include the low cost of the utensils and the location in which they were purchased, constituting major commercial hubs of Greater São Paulo. Socioeconomic aspects such as educational level, income bracket, besides other factors, are known to be directly associated with a host of chemical exposure scenarios (Carvalho et al. 2017). Shoppers often travel to these commercial centers to buy this type of product and thus exposure to these Pb and Cd-contaminated items extends beyond the local population.
The highest migrations were detected for acetic acid 3% solution (m/v), with 99.9% of utensils exhibiting specific migration that exceeded permitted limits for both Cd and Pb (Table 6). Whitt et al. (2015) investigated specific migration of heavy metals from recycled polyethylene terephthalate using deionized water as the simulant solution. The levels of Cd and Pb which migrated into the simulant proved below the limit of detection of the method. In the present study, levels of migration of Cd exceeded allowed limits for 54.55% of the utensils tested, with an even higher proportion for Pb, at around 91% of items tested. All of the migration test results using simulant solutions exceeded the allowed levels established by Brazilian law of 0.005 mg.kg−1 and 0.01 mg.kg−1 for Cd and Pb, respectively. No contamination was detected in the analytical blanks, thus confirming the major potential bioaccessibility of the metals previously quantified in loco using XRF analyses (Table 5).
The migration tests on consumable beverages were performed for Pb only. The results found for these tests were even more alarming (Table 7). For orange juice, migration values were 360 times higher than the legally allowed limit, while all the other beverages also exceeded migration limits on tests for sample fragment area and overall area of both cups and mugs. These beverages were chosen because they are routinely consumed by children using the utensils in both home and school environments, where children can spend up to 10 hours a day at day care centers (Olympio et al. 2018). Notably, the analyses of commercial beverages showed they contained Pb and Cd levels which were below the limit of detection.
Many authors have implicated plastic objects as potential sources of exposure. Turner (2018) analyzed around 200 toys made of recycled plastics in the European Union and found high levels of PTEs in the base material. In a study conducted in Kazakhstan, Akimzhanova et al. (2020) found levels of lead contamination in children´s plastic jewelry of 50 mg.kg−1. Guney and Zagury (2013) investigated bioaccessibility of both Pb and Cd in plastic toys and found values in the 642-647 mg.kg−1 range for Pb and 1.31-1.34 mg.kg−1 for Cd. In a Chinese study of specific migration of lead in plastic toys, Kang and Zhu (2015) found a level of 95 mg.kg−1. Cui et al. (2015), in a study of bioaccessibility of Pb in toys from the Chinese market, found levels of 3.19 mg.kg−1 for Pb and 0.86 mg.kg−1 for Cd. All of the above-cited studies, consistent with the present investigation, confirmed plastic toys and jewelry as a potential source of Cd and Pb exposure, as well as domestic utensils routinely used for feeding children.
The International Agency for Research on Cancer (IARC 1993) classifies Cd as a substance carcinogenic for humans whose childhood exposure is associated with adverse health effects in adult life, such as renal problems (Schoeters et al. 2006). Moreover, the United States Centers for Disease Control (CDC) has established a blood lead reference value of 5 µg.dL−1, calculated according to the 97.5th percentile based on the National Health and Nutrition Examination Survey (NHANES) (CDC 2012). However, the toxic effects of lead can be seen in children at concentrations lower than this reference value. According to Paulson and Brown (2018), this value is in the process of being revised to the lower limit of 3.5 µg.dL−1. Plastic utensils are one of many sources and routes of exposure for children. In a study of 50 day care centers with 2397 children, the authors found blood lead levels of around 2.16 µg.dL−1 and a 97.5th percentile of 13.9 µg.dL−1 (Olympio et al. 2015; Olympio et al. 2018). In a later investigation involving a subsample of the Olympio et al. (2018) study, Silva et al. (2018) explored potential sources of lead exposure, identifying sources that included paint coatings of walls, floors, doors, windows, as well as plastic toys and utensils handled by children at day care centers and within their homes. Other studies have investigated the associations of blood lead levels with exposure of children aged 1-4 years by analyzing 24h diet in school and household settings. The results showed Pb levels of 2.71 µg.dL−1 in blood, 1.61 – 2.24 µg.kg−1 in the diet, and bioaccessibility for Pb, Cd and As of 0.18 ± 0.11 µg.kg−1, 0.08 ± 0.04 µg.kg−1 and 0.61± 0.41µg.kg−1, respectively (Leroux et al. 2018a; Leroux et al. 2018b). In addition, another route of exposure to these metals occurs in the form of informal home-based work. For example, in the production of jewelry and fashion jewelry in the city of Limeira, São Paulo state, children or other members of the household are exposed to elements such as Pb, Cd, As, among others (Ferreira et al. 2019; Pereira et al. 2020; Salles et al. 2021).
Therefore, there is a clear need for further studies investigating plastic utensils for use by children as a source of exposure not only to Cd and Pb, but also to other PTEs these materials may contain. Moreover, as outlined previously, contamination of these materials by Cd and Pb is not a problem specific to Brazil, but an issue documented in many other countries including the USA, China and Kazakhstan (Guney and Zagury 2013; Kang and Zhu 2015; Cui et al. 2015; Turner 2018; Akimzhanova et al. 2020). In the present study, a large proportion of the plastic utensils tested were imported, predominantly from China, a major trading partner for Brazil.
Only the simulant solutions of water and acetic acid 3% (m/v) were employed in the present investigation. Official Brazilian guidelines recommend that, for fatty foodstuffs such as milk, ethanol-based solutions be used at the appropriate concentrations according to the type of food under analysis. It is important to point out, however, that the regulatory body states that the use of acetic acid 3% (m/v) as a simulant solution suffices for performing migration tests. Another important factor is the temperature at which experiments are conducted, where suggested temperatures are provided by the legislation and EN standards cited.