Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: THURSDAY, January 13, 1994                   TAG: 9401130064
SECTION: CURRENT                    PAGE: NRV-7   EDITION: NEW RIVER VALLEY 
SOURCE: Joe Hunnings
DATELINE:                                 LENGTH: Medium

TO LIMIT INTAKE OF CARCINOGENS, HOLD THE PESTO ON THAT PASTA

Pesto's primary ingredient is basil, which is loaded with estragole. The estragole is not only responsible for that unforgettable flavor; it's also a carcinogen in rodents.

Surprised? Well, hold onto your seat, because basil is just the beginning.

Mustard contains allyl isothiocyanate; comfrey contains symphytine; and mushrooms contain various hydrazines, all of which are carcinogens with higher potencies in rats or mice than polychlorinated biphenyls, or PCBs.

It seems that virtually every plant contains natural compounds that act as protection against insects, micro-organisms and herbivores. About half of these compounds have proved to be carcinogenic, at least in rats or mice. And we consume about 10,000 times the amount by weight of these natural pesticides as we do synthetic pesticide residues.

We encounter many other naturally occurring sources of carcinogens every day. Many carcinogens are created during cooking. Our own bodily metabolism is responsible for the release of carcinogenic oxygen radicals.

The large number of naturally occurring carcinogens is likely to overwhelm any effect from the small amounts of synthetic pesticides we consume. While this doesn't mean we should ignore the cancer risk of synthetic pesticide residues, it does put it into perspective. Should we panic about a trace amount of ethylene dibromide (an agricultural fumigant) when the pesto packs a stronger punch?

Another thing to remember is that when we consume synthetic pesticide residues and natural pesticides, we generally consume them on or in fruits and vegetables. Fruits and vegetables also contain anti-carcinogens, including vitamins E and C and beta-carotene. These anti-carcinogens, combined with your body's defenses, protect against both natural and synthetic carcinogens.

Of course, it makes sense to eliminate the largest risks from one's diet and environment. To do that, we need to be able to measure the degree of carcinogenicity. Unfortunately, most of the data is for rodent, not human, carcinogens.

In fact, it is impossible to calculate human risk based on rodent exposure data, but the rodent data can serve as a guide to informed decisions. Prudence would dictate limiting substances that are highly potent rodent carcinogens.

Bruce Ames and his colleagues at the University of California have developed a scale to compare carcinogens based on human exposure and rodent carcinogenicity. While this scale does not calculate risk, it does point out that the greater the human exposure to the rodent carcinogen or the greater the potency of the carcinogen in rodents, the higher the human exposure/rodent potency ratio.

According to Ames' table, exposure to the air inside a conventional house for 14 hours a day yields an HERP of 0.6 percent (from formaldehyde in some insulating materials), while the HERP for the daily dietary intake of PCBs in the United States is just 0.0002 percent. (The HERP for mobile-home air, 14 hours per day, is 2.1 percent.)

One raw mushroom weighing 15 grams would have a HERP of 0.1 percent (from hydrazines), while HERP reulting from the U.S. average daily dietary intake of ethylene dibromide (the agricultural fumigant) is 0.0004 percent.

A sandwich containing 32 grams of peanut butter with an aflatoxin content of 64 milligrams would have a HERP of 0.03, and a 12-ounce beer comes up with a HERP of 2.8 percent. In fact, the data shows that a can of beer exposes you to a larger amount (based on body weight) of a rodent carcinogen than does your average intake of PCBs, DDE/DDT and ethylene dibromide combined.

Based on the available data, it's impossible to say that a synthetic pesticide is more or less likely to cause cancer than a natural pesticide. The HERP figures only suggest a lower risk from synthetic pesticide residue. They don't prove it.

It seems reasonable to conclude that occupational exposures in high concentrations of synthetic chemicals and indoor air pollution may be a much greater risk than either natural or synthetic pesticides in the diet.

It appears that we continually are bombarded by carcinogens in our diet and have been throughout our history. Remembering this may help us keep our perspective on the carcinogenicity of pesticide residues, especially when there is much that could be done to reduce such major sources of cancer as smoking and occupational exposure.

Relatively speaking, pesticide residue is a minor cause of cancer and may even be irrelevant when considering the vast number of natural pesticides with similar or greater potencies.