Tempered glass dinnerware is free of lead and has no negative effects on the human body. Because glass is a high-temperature sintering result of silicate, it is non-toxic, and the purpose of cleaning glass goods is primarily to remove contaminants from the glass's surface. Certain substances can cause problems for people with certain medical conditions; for example, some medications can be harmful if taken by someone with kidney disease. In general, glass is not toxic to healthy humans. However many chemicals can become toxic when they are absorbed into the blood stream through cuts or wounds on the skin. These chemicals include mercury, lead, and arsenic. The risk of exposure to these toxins via consumption of food that contains minute traces of them is extremely small. If you are concerned about whether or not eating glass may be harmful to your health, research has shown that the level of toxicity depends on the material itself as well as how it was made. For example, glass made in factories using coal gas as an ingredient will be more toxic than glass made with natural gas. In addition, minerals such as iron and calcium found in some glasses may also add to their toxicity. Finally, heat treatment used to make glass products inactive elements present in some raw materials that would otherwise remain active can increase their toxicity.