As long as composite fabric clothing is produced by a reputable manufacturer and the hangtag displays the mandatory safety standard GB 18401-2010 "National Basic Safety Technical Specifications for Textile Products" (and the mandatory standard applicable to infant and children's clothing GB 31701-2015 "Safety Technical Specifications for Infant and Child Textile Products"), there's no need to worry about it being "toxic." When purchasing fleece-lined clothing, choose reputable merchants and brands, and check the product's quality inspection report to ensure the safety of the fleece-lined pants. During the selection process, you can make a preliminary assessment of the clothing's safety through simple observation and judgment: From the smell, if you detect a pungent odor, do not buy it; normally, fleece-lined clothing should not have any odor.
From the appearance, high-quality fleece-lined clothing is usually soft, evenly colored, and has abundant fleece that does not easily shed; inferior fleece-lined clothing has rough fabric, uneven color, sparse fleece that easily sheds. When purchasing composite fabrics used in industries such as automotive seats, pay attention to specific properties such as seam strength and flame retardancy.