This is from A Consumer's Dictionary of Food Additives
The entries are long so I only included what I thought would be of
most interest.

Potassium Metabisulfite

...It is an antioxidant, preservative, and antifermentative in
breweries and wineries.  Should not be used in meats or foods
recognized as sources of vitamin B1.... Low toxicity... report to FDA
of the Select Committee on GRAS Substances (GRAS = generally
recognized as safe) stated in 1980 that ... it should continue its
GRAS status with limitations on the amounts that can be added to
foods.

Additionally in the sulfites entry:

Potassium metabisulfite is one of 6 sulfiting agents currently listed as GRAS.
Currently these agents may be used as preservatives in any food
except recognized sources of vitamin B1.

Reaction to sulfites can include acute asthma attacks, loss of
consciousness, anaphylatic shock, diarhea, and nausea .....  There
have been seventeen deaths that the FDA has determined were "probably
or possibly" associated with sulfites.  FDA banned the used of the
preservative on fresh fruits and vegetables and is reviewing (at
1999) a proposal to prohibit it on fresh, precut potatoes.  The FDA
decided in 1988 against extending its ban on the use of sulfites to a
variety of foods sold in supermarkets and served in restaurants,
including wine, dried fruit, some seafood, and condiments.  Sulfites
must be declared on the labels of wine and packaged foods sold in
supermarkets when they are added in excess of 10 ppm.

Numerous prepared foods are listed in the CDFA as containing sulfites
and consumers are warned to be cautious if sulfite sensitive.

Most significant in sulfur dioxide residues are
dehydrated potatoes, dried fruit, fruit juice (concentrated), fruit
juices (regular strength), molasses and nut products.

Mike Raiti
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