Although traditionally made of steel, the reinforcement can also be made of a composite material, a plastic such as thermoplastic polyurethane (TPU) or even aluminum. Steel-toe boots are important in construction and manufacturing, as well as a variety of other industries. Occupational safety and health legislation or insurance requirements may require the use of such boots in some settings, and may mandate certification of such boots and the display of such certification directly on the boots. The markings on the boot label will indicate the national or international standards that the boot was intended to meet, and identify the level of protection offered for impact, compression, penetration, and electric shock. Safety shoes are effective in keeping the feet of industrial workers safe from sharp and heavy objects while working in factories. Footwear for use in chemical processing or semiconductor manufacturing may also be rated to dissipate static electricity.