Perhaps your old aluminum pots are heirlooms inherited from a loved one, but appreciating them as decorative gifts may be better than putting them to practical use. The constant heating and cooling of old aluminum cookware slowly wears away their cooking surfaces with each use. Since aluminum is a soft metal, these pots become worn over time, and concerns arise about the effects of metal residues and safe handling of these pots at high temperatures.
Aluminum cookware is light and easy to handle, but a major concern with these pots is metal leaching into food cooked in them. According to the University of Wisconsin-Madison, aluminum in its pure form is a very soft, malleable, active metal that is often combined with other minerals and metals, such as magnesium, copper and silicon, to make harder aluminum alloys.
Aluminum is regarded as a non-toxic metal, since it is Earth's most abundant metal, but in combination with other metals, and with its leaching into food through cooking, it can lead to aluminum poisoning. Since aluminum is a readily reactive metal, cooking acidic foods such as lemons and tomatoes in aluminum pots activates the aluminum to change into a more soluble form. The soluble aluminum mixes into the food as it cooks. High levels of aluminum in the body can cause neurological and respiratory problems, according to the Agency for Toxic Substances and Disease Registry.
Aluminum's soft and malleable properties make it hazardous to use at high temperatures, especially for older, worn pots. Empty aluminum pots heated at high temperatures for a long time can melt and become molten aluminum. In this "boil dry" state, it can cause severe burns and ignite a fire, according to the U.S. Consumer Product Safety Commission. There is more of a risk of the "boil dry" effect when using older pots that have lost some of their durability.
Another concern about using old aluminum cookware is its connection to Alzheimer's disease. The actual role that aluminum toxicity plays in Alzheimer's disease is inconclusive, as cited by Michigan State University Extension and Clemson University. However, The Biology Project and The University of Arizona clearly cite from a study by D.R. McLachlan and colleagues that, "It was found that a relationship did exist between the number of diagnosed AD cases and the level of aluminum present in the drinking water supply."