I've seen claims that canned food is bad for your health, because the linings often contain Bisphenol A (BPA). Is that true?
Please back up your answers with reliable references.
There are two sub-questions that must be addressed here.
Is BPA used in can linings, and can it leach into food?
This is definitely true. The National Institute of Environmental Health Sciences (part of the NIH), for example, says that
Polycarbonate plastics have many applications including use in some food and drink packaging, e.g., water and infant bottles, compact discs, impact-resistant safety equipment, and medical devices. Epoxy resins are used as lacquers to coat metal products such as food cans, bottle tops, and water supply pipes.
These epoxies are what is used in the cans for canned foods, and they contain BPA. It subsequently leaks out in minute quantities, although this is thought to be related to the temperature of the can, not aging.
Is BPA a hazard to human health?
This is not quite as clear. The FDA has changed its stance over time as new research showed different conclusions. Its most recent memo reviewed previous studies. One recent one found that adults are exposed to about 0.2 micrograms of BPA per day, while young children and infants are exposed to about 0.5 micrograms per day.1 However, other research had shown that hazardous levels were in general orders of magnitude higher than these doses. Thus, in the FDA's most recent findings, BPA in food cans is not a problem. However, the agency has made it clear that it continues to revise its recommendations as new information is available.2
None of this should be taken to mean that BPA is not hazardous to humans. Higher amounts can prove toxic, as the chemical is thought to disrupt the endocrine system (see Rochester (2013) and Ihde et al. (2015)). This can, in some cases, lead to severe effects, possibly including cancer, and especially when applied to children. It may also cause neurological harm (see Negri-Cesi (2015) and Inadera (2015)).
In short, while BPA may pose a threat to humans in high enough quantities, its presence in canned food linings does not appear to be dangerous.
1 This drastic difference is due to the previous use of BPA in some drinking containers used by infants. The FDA has banned this, but because industry leaders had stopped using it due to consumer pressure, not because of clear health concerns.
2 The European Food Safety Authority (EFSA) has echoed the FDA's conclusions; see Ćwiek-Ludwicka (2015).