As a new school year approaches, parents may be busy selecting new shoes for their children in preparation for the start of term. In the Consumer Council’s test on 28 models of primary school shoes, various harmful substances were detected in 13 models, including the carcinogen chromium VI, aromatic amines, formaldehyde, and the reproductive toxicant phthalates. Among them, 4 models’ chromium VI or phthalate levels exceeded European Union (EU) limits, with 1 found with phthalate levels nearly 86 times above the upper limit, posing even higher health risks to children with wounds or eczema on their feet. Durability test results also vastly varied, with 2 models showing cracks after 35,000 or 50,000 flexes respectively, while others exhibited issues such as insufficient adhesion between the shoe upper and sole, as well as poor abrasion resistance of the outsole. The Council urges manufacturers to improve design and materials of school shoes to better protect children's feet and promote healthy growth.
The Council purchased 28 models of primary school shoes from various retail outlets with an equal number of male and female styles, of which 18 models had animal leather components. Prices ranged from $198 to $599. Tests comprised 2 parts: chemical safety and physical performance. The chemical safety tests measured levels of chromium VI, phthalates, aromatic amines from azo dyes, formaldehyde, and dimethylfumarate (DMF). The chromium VI and DMF tests were only conducted on models with animal leather. Physical performance test items included flexing durability, adhesion between shoe upper and sole, outsole abrasion resistance, outsole slip resistance, breaking forces of straps, buckles, and related accessories, as well as sharp points and edges.
2 Models Contained Carcinogenic Chromium VI at Levels Exceeding EU Limit
Chromium VI is typically formed through oxidation of chromium III compounds used in leather tanning. As it can cause cancer in the lungs, the International Agency for Research on Cancer (IARC) has classified it as a Group 1 “carcinogenic to humans” agent. Using leather containing chromium VI could cause rashes, ulcers, and allergic reactions resulting in contact dermatitis. The EU REACH regulation limits chromium VI content in finished leather parts that come into contact with skin to be no more than 3mg/kg of its total dry weight. 2 models were detected with 4.5mg/kg and 5.0mg/kg of chromium VI in their lining respectively, both exceeding the EU limit. Although children generally wear socks with shoes, the risk of contact with chromium VI in shoes cannot be completely ruled out. If parents notice persistent rashes or dermatitis on their children’s feet, stop wearing the shoes suspected to be the cause and seek medical attention promptly.
2 Models Exceeded EU Limit for Phthalates
with 1 Over by 86 Times
Phthalates (DEHP, BBP, DBP, and DIBP) are all classified as Category 1B reproductive toxicants, with animal experiments showing harmful effects on sexual function, fertility, and development, also displaying endocrine-disrupting properties that can affect human hormone levels. The EU REACH restricts the total concentration of phthalates, either individually or in any combination, to be no more than 0.1% in plasticised materials in products. 4 models were detected with DEHP or DBP, of which 1 had a DEHP concentration of 8.69% in the insole, exceeding the EU limit by nearly 86 times. Another contained DBP in the insock (0.37%) and insole (0.01%), the former exceeding the EU limit by about 2.7 times. Detected DEHP concentrations in the remaining 2 models did not exceed the EU limit. Generally, plasticisers are not readily absorbed by human skin, but with wounds or eczema the risk of absorption increases. Parents should also teach their children to wash hands after putting on or taking off shoes to avoid indirect ingestion of plasticisers through contact with the mouth or food.
4 Models Contained Harmful Aromatic Amines
8 Found with Formaldehyde but Under Limit
If azo dyes are used in shoe production, they may release carcinogenic or allergenic aromatic amines. EU REACH stipulates that if concentration of specified aromatic amines in finished products or dyed parts exceeds 30mg/kg, they cannot be used in textiles or leather products that come into direct and prolonged contact with the skin or mouth. Among the 4 models detected with aromatic amines, 3 had concentrations below the limit, while the remaining 1 contained 32mg/kg of 4,4'-diaminodiphenylmethane (MDA), one type of aromatic amines which is classified by IARC as a Group 2B agent (possibly carcinogenic to humans). However, tests indicated that the MDA was not released from azo dyes but may have originated from other raw materials. Given the inherent hazards of such substance, this model received a lower score in the test.
Tests also found that 8 models contained formaldehyde, but none exceeded the EU REACH limit of 75mg/kg. None of the models were found to contain DMF either, which may irritate skin and cause allergies.
Durability Varied 2 Models Cracked After Bent Tens of Thousands of Times
Children are active and energetic thus school shoes, worn almost daily, must also be durable. The flexing durability test simulated daily walking conditions, with reference to the SATRA TM92 testing method from the Shoe and Textile Research Association (SATRA) Centre for Footwear and Related Industries. Each model was repeatedly flexed along its natural bending line. 1 showed a 7mm gap between the upper and outsole at the outer edge of the forefoot, along with a 65mm crack in the outsole after 35,000 flexes. After 50,000 flexes, these issues worsened to 13mm and 86mm respectively, with an additional 5mm separation between the upper and outsole at the inner side. Another model showed a 16mm gap between the outer side of the upper and the outsole after 50,000 flexes.
In the adhesion strength test between the upper and sole, 4 material specimens containing both the upper and sole sections were obtained from each model. The upper and sole sections of the specimens were then pulled apart by tensile force, and the force required per millimetre width (N/mm) was calculated, with higher values indicating better adhesion. Results showed that 3 models performed better, with average adhesion strengths ranging from 9.4 to 11.9, while the 5 poorer-performing models averaged only 2.3 to 2.6. Additionally, 1 model had an adhesion strength of only 0.4 at the inner side of the left shoe, significantly lower than that in other areas of the same pairs of shoe.
In terms of abrasion resistance of the outsole, 4 models exhibited relatively more severe wear (abrasion volume ranging from 619.9mm3 to 664.3mm3), compared to the 4 better-performing samples (42.8mm3 to 93.5mm3), varying by up to over 14 times. As for slip resistance of outsoles, all models performed satisfactorily. However, the test only reflected slip resistance on specific surfaces and may not cover all daily walking scenarios, so parents should choose based on actual needs.
When purchasing school shoes for children, consumers may consider the following tips:
- Children should always try shoes on in person to test standing and walking, as well as squatting to check if the shoes are pressing against the toes. Additionally, test whether the front of the shoes can be easily bent by hand, as excessively stiff shoes may be uncomfortable to walk in;
- It is not recommended for children to wear shoes one size up. Toe boxes should have a maximum empty space of approximately 0.5cm to 1cm. Too much space may cause children to inadvertently grip the shoe with foot muscles and toes to minimise slippage, preventing the feet from relaxing and tiring or discomfort may result. Slippage also increases the risk of skin abrasions;
- Avoid pointed-toe shoes to prevent bunions and adverse foot development. Choose round-toe or wide-toe shoes, with heels preferably less than 2cm high;
- Children aged 4 to 13 typically grow half a foot size every 4 months, but replacement frequency should be adjusted according to individual growth rate. Parents may need to budget for 2 pairs of shoes annually.
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