A pediatric health risk assessment of children's toys imported from China into Nigeria

Overview

This Heliyon paper measures total Pb, Cd, and As in the surface-paint coatings of 30 low-cost “made in China” children’s toys purchased from supermarkets and street vendors in Port Harcourt, Nigeria, by flame atomic absorption spectrophotometry (PerkinElmer AAS-700) after concentrated HNO₃ digestion. All thirty samples report measurable Pb (4.16–9.747 mg/kg), Cd (1.942–6.50 mg/kg), and As (1.459–6.318 mg/kg) in the scraped paint, with every value below the EU Toy Safety Directive 2009/48/EC migration limits cited by the source as 90 mg/kg (Pb), 23 mg/kg (Cd), and 47 mg/kg (As). USEPA-style oral and dermal hazard quotients (HQ), total target hazard quotients (TTHQ), hazard indices (HI), and lifetime cancer risks were computed using exposure parameters from the Risk Assessment Information System (RAIS) for a 6-year-old, 15-kg child; all HQ/HI values are below 1 (HI range 0.126–0.409) and all total cancer risk values are within the 1×10⁻⁶–1×10⁻⁴ acceptable range. The authors conclude that these particular “made in China” toys lately imported into Nigeria do not add measurably to children’s body burden of these metals, while noting that bioaccumulation under chronic exposure may still be relevant — particularly for Pb, which has no safe blood level.

Key numbers

All metal concentrations are total elemental Pb, Cd, and As in scraped surface-paint coatings of finished toys, measured in triplicate by flame atomic absorption spectrophotometry (PerkinElmer AAS-700) following concentrated HNO₃ digestion. Per-sample paint mass ranged 15–25 mg before digestion to 25 mL final volume. Units in mg/kg of paint coating.

Per-sample concentrations (Table 3, p. 3; N = 30)

EU Toy Safety Directive 2009/48/EC migration limits cited in the same table for reference: Pb 90 mg/kg; Cd 23 mg/kg; As 47 mg/kg.

Distribution summary across the 30-sample set (computed from Table 3; source-reported ranges)

The source does not report per-metal mean, SD, or percentile statistics for the 30-sample set; it reports the range (min/max) only.

Exposure-assessment parameters (Table 1, p. 2; with rationale from RAIS and USEPA)

Reference doses and cancer slope factors used (Table 2, p. 3)

Sources: RAIS (2013) for Pb dermal/CSF oral and As; Walkes and Rehm (1994) for Cd CSF oral; AERIS Software Inc. (1991) for Pb oral, Cd, As oral RfD and Cd dermal RfD. Pb dermal CSF and Cd dermal CSF are not reported by the paper (entered as ”—” in Table 2).

Hazard quotient, total target hazard quotient, and hazard index (Tables 4 + 5; selected high/low samples)

Per-sample oral CDI, oral THQ (Pb/Cd/As), oral TTHQ (sum), dermal CDI, dermal THQ, dermal TTHQ, oral and dermal cancer risk, total cancer risk (TCR), and total hazard index (HI = oral TTHQ + dermal TTHQ) for all 30 samples are tabulated in Tables 4 and 5 of the paper.

Across-sample range summary computed from Table 5 of the paper:

Source-body summary statement (Discussion p. 4): “The HI of Pb, Cd and As from via oral and dermal routes ranged from 0.126–0.409 indicating es no significant non-carcinogenic health risk. The total cancer risk (TCR) of Pb, Cd and As were within the generally acceptable risk range of 1.4 × 10⁻⁴ – 1.4 × 10⁻⁶.” The HI range matches the per-sample table. The TCR-range bounds the source reports in the body (1.4 × 10⁻⁴ – 1.4 × 10⁻⁶) do not exactly correspond to the per-sample TCR min/max in Table 5 (4.5 × 10⁻⁵ – 1.5 × 10⁻⁴); the body wording appears to invert min/max ordering and the upper bound 1.4 × 10⁻⁴ is close to but not the same as the per-sample max 1.5 × 10⁻⁴. The acceptability conclusion (all TCR < 1 × 10⁻⁴ acceptable-upper-bound threshold) holds at the per-sample level: every per-sample TCR in Table 5 is between 4.5 × 10⁻⁵ and 1.5 × 10⁻⁴, with most samples below 1 × 10⁻⁴.

Comparative literature values reported by the source (Discussion, p. 4)

The authors interpret their lower values, relative to the two earlier Nigerian datasets (Omolaoye 2010, Oyeyeola 2017), as evidence of a downward trend in toy heavy-metal contamination over the decade following the 2007 US CPSC recall of ~6 million toys and the subsequent strict CPSC regulation of Pb in children’s products (and the 2010 ~12-million McDonald’s-cup Cd recall and the 2010 voluntary bracelet recall). Studies elsewhere (Hillyer et al. 2014, Mateus-Garcia and Ramos-Bonilla 2014, Cui et al. 2015, Negev et al. 2018) are cited as also reporting higher levels than this study.

Methods (brief)

Sampling (Section 2.1, p. 2). Market-basket method. Thirty low-cost “made in China” toys purchased January–February 2018 from supermarkets and street vendors in Port Harcourt, Nigeria. Plastic toys included teethers, balloon, toy cars/planes, and rattles; brittle/pliable items included playdough, crayon, and watercolour pen. Paint coatings were scraped from a plastic toy car and from building blocks.

Sample preparation (Section 2.2, p. 2). Toy surface paint was removed by scraping with clean razor blades; fresh blades and underlying paper were used for each toy to prevent cross-contamination. Per-sample paint mass 15–25 mg. Samples placed in test tubes with 5 mL trace-metal-grade nitric acid and two small boiling chips. Initial heating at 90–100 °C until fuming stopped, then vigorous digestion in an oil bath / heating block at >120 °C for 3 h (Weidenhamer 2009). Samples cooled and diluted to 25 mL in volumetric flasks with four 4-mL water rinses; settled ≥0.5 h before analysis; further dilution with 5% trace-metal-grade HNO₃ if needed to fit the calibration range.

Instrumental analysis (Section 2.2). Pb, Cd, and As concentrations measured in triplicate using a PerkinElmer AAS-700 atomic absorption spectrophotometer (flame mode per the AAS-700 designation; the paper does not specify graphite-furnace or hydride-generation modules for As, though hydride generation is the conventional approach for As at this concentration range — this is a methods gap the paper does not address).

Speciation. Total elemental Pb, total Cd, total As. No speciation of inorganic vs organic As (no iAs/tAs distinction). The paper’s discussion of As toxicity invokes inorganic-As carcinogenicity (skin, lung, liver, bladder cancers) implying inorganic As as the toxicologically relevant species, but the analytical method measures total As without speciation, and the toxicological assumption is read into the risk assessment by using the inorganic-As oral CSF (1.5 (mg/kg-day)⁻¹) against total As measurements.

Quality control (Section 2.3). Method accuracy validated using soil Certified Reference Materials TraceCERT® 16595 (Pb), 51994 (Cd), and 39436 (As). CRM analysis results required to fall within the 95% confidence interval of the corresponding certified values. Relative standard deviation (RSD) measured in triplicate CRM analyses under repeatability conditions; reported RSD between replicate analyses <4%. The CRM was also used as a quality-control sample in each measurement series. No LOD/LOQ values explicitly stated.

Risk assessment framework (Sections 2.4–2.8). USEPA model per Risk Assessment Information System (RAIS) 2007, supported by USEPA IRIS toxicological profiles and the US ATSDR toxicological profile series. Oral and dermal Average Daily Intakes computed per Equations 1 and 2. Non-carcinogenic risk via target hazard quotient THQ = ADI/RfD (Eq. 3) and hazard index HI = ΣHQᵢ (Eq. 4). Carcinogenic risk via Riskₚₐₜₕ𝓌ₐᵧ = Σ ADIₖ × CSFₖ (Eq. 5); total risk Risktotal = Riskoral + Riskdermal (Eq. 6).

Implications

Certification. Direct A-tier occurrence data on the paint-coating Pb, Cd, and As burden of cheap China-import toys sold at the bottom of the Nigerian retail market in 2018. The 4.16–9.747 mg/kg Pb / 1.942–6.50 mg/kg Cd / 1.459–6.318 mg/kg As ranges are an order of magnitude or more below the EU 2009/48/EC migration ceilings (90 / 23 / 47 mg/kg) the source cites, but for Pb the 4-to-10 mg/kg paint-coating values are substantially above the US CPSIA paint-Pb limit of 0.009% w/w (= 90 mg/kg in paint by weight, equivalent to the EU value the source cites; the CPSIA 0.009% figure cited in the source’s Discussion p. 4 from Library of Congress 2008 supersedes the earlier 0.06% / 600 ppm value). The sample-set’s positioning in the low end of comparable Nigerian and Malaysian datasets (Omolaoye 2010 Pb up to 1,445; Oyeyeola 2017 Pb up to 106; Ismail 2017 Pb up to 172) is a direct input to HMTc Cat 21 Row 1 (general toys with paint/surface coatings) pooling once that row’s Step 0 lock is authored. The dataset does not measure migration (the test of regulatory record per EU 2009/48/EC); it measures total elemental content in scraped paint, which is an upper-bound surrogate for bioavailable Pb/Cd/As under oral mouthing or dermal contact.

Courses. Useful teaching case for (a) USEPA THQ/HI/CSF risk-assessment methodology applied to non-food consumer-product surfaces, (b) the gap between “below regulatory migration limit” and “no biologically relevant exposure” at the child age × low-body-weight × high-mouthing-frequency intersection, and (c) the methods-gap between AAS measurement of total As and the inorganic-As CSF used in the risk arithmetic. The dataset is also a useful comparator for showing the magnitude of variability in Pb-paint toys across studies and time periods — three orders of magnitude between Omolaoye 2010’s upper-tail (1,445 mg/kg) and the present study’s lower-tail (4.16 mg/kg).

App. Per-toy-format paint-coating Pb, Cd, and As distributions are direct input for any future app feature estimating contamination likelihood in painted children’s toys imported from Chinese manufacturers into West African or comparable markets. The HI 0.126–0.409 range (combined oral + dermal at the 6-year-old, 15-kg child reference) is the source’s own acceptability-tier output; the absence of per-metal mean/SD/percentile statistics across the 30-sample set is a data-quality limit on per-format probabilistic modelling.

Microbiome. Not addressed by this source.

Related evidence

• Lead
• Cadmium
• Arsenic
• General toys with paint/surface coatings
• Considerations when Estimating Exposure to Crafts and Toys in Children (OECD Series on Testing and Assessment No. 401)

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