of the world—but these are also the bigusers of plastics. Production of polystyrenebegan just prior to World War II; pancreatic cancer has increased rapidly sincethat time. Not noted in your article is thefact that chemists, dry-cleaners, and handlers of gasoline have a relatively high incidence. These workers have in commonthe fact that they handle chemicals that arestrong solvents for polystyrene and mightdrink beverages from plastic with fumespresent or hands contaminated.

Some coffee drinkers sense that thetaste is perceptibly different from a plasticcup. If small amounts of the plastic dodissolve, a reaction might occur with someother agent (possibly chlorine) to producea carcinogen. Worrisome is the fact thatcertain foods are known to be solvents forpolystyrene, including citrus oils, butter,and coconut oil (an ingredient in some coffee creamers!). Although only coffee hasbeen singled out statistically, the class ofpeople at special risk for pancreatic cancermay be—not coffee drinkers—but theingesters of melted polystyrene.

Shirley F. HansenAdministrative OfficerVeterans Administration Medical CenterLake City, Florida

Dr.BrianMacMahon'sReply:

Following publication of our paper' reporting an association between coffee consumption and pancreatic cancer, wereceived a good deal of helpful correspondence suggesting underlying mechanisms.The leaching of polystyrene from disposable cups suggested by Ms. Hansen wasmentioned by a number of people, but byfar the most frequently mentioned possibleagents were pesticides contaminating imported coffee beans. Other suggestions included contamination of beans withantimony ore during shipping and a number of contaminants of the water used tobrew coffee. Since there are also over I ,000chemicals in coffee, including known mutagens, there will be no shortage of hypotheses to be tested if the existence of the

association is confirmed. Our own view,though, is that work to evaluate the association further is needed before we worrytoo much about possible mechanisms.

Brian MacMahon, M.D.ProfessorHarvard School of Public HealthBoston, Massachusetts

Reference

I. MacMahon B, Yen S, Trichopoulos D, etal: Coffee and cancer of the pancreas. N EnglJ Med 304:630—633,1981.

Retinoblastoma

To theEditor:

In the article on retinoblastoma (Ca32:130—140, 1982), Dr. Abramson statesthat it occurs in one in 18,000 to 30,000live births. In your January/February statistics issue (Ca 32:30, 1982), the incidence of retinoblastoma is indicated to bethree per million children.

There seems to be a discrepancy. Pleaseexplain.

Marvin Shapiro, M.D.Encino, California

Author'sReply:

I chose to include the article from the Archives of Ophthalmology to reference theincidence of retinoblastoma, because it isthe most recent reference on this subject,and I thought that readers could use this tofind additional references they might like.Unfortunately, that article did not expressthe occurrence in terms of number of livebirths, and that is the discrepancy notedby Dr. Shapiro.

I might point out that the SEER of theNational Cancer Institute is very valuable,but for retinoblastoma, worthless. As canbe seen in Ca, according to SEER's statistics, only 58 cases were seen in the coun

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