amounts. Conversely, highly toxic materials may pose no hazard when exposure is
minimal.Maximum Residue Levels and Acceptable Daily IntakeFor most of us, the primary exposure is what we eat and drink. Maximum Residue
Levels (MRL) and Acceptable Daily Intake (ADI) are measures set by the federal gov-
ernment to assure us that human exposure to pesticides is limited. But there is no
foolproof way to ensure a safe, universal ADI because of the diversity of food we eat
and because some people are more vulnerable than others, especially young children
and the malnourished. MRLs and ADIs also do not take into account the effects of
combinations of pesticides or of pesticide breakdown products.
Very little research has been done to determine safe intake levels for the degrada-
tion chemicals of agricultural poisons. Consequently, there are virtually no safety lev-
els to determine the ADI of toxic breakdown chemicals that contaminate our food.‘‘Legal’’ Does Not Equal ‘‘Safe’’Fortunately, most pesticide residues detected in or on foods are within the legal
limits established by the EPA. Does that mean the residues are ‘‘safe’’? Not at all.
Why is food safety an ephemeral concept? There are several explanations. First, toler-
ances were set, often many years ago, by estimating maximum residues on foods after
pesticide treatments. Most tolerances for older pesticides were set with little or no
assessment of risks to human health, but were intended as a basis for monitoring to
ensure that pesticide uses were in accord with label directions. Also, since tolerances
are the only legal limits for residues in domestic or imported foods that the govern-
ment sets, federal law and many scientific advisory bodies have directed the EPA to
use them to keep dietary pesticide exposure to within ‘‘safe’’ limits. However, U.S.
pesticide legislation also required the EPA to balance the goals of permitting pesticide
use and protecting human health. Consequently, many tolerances were set at levels
higher than safety concerns alone would require.
The FQPA requires that pesticide exposures be ‘‘safe,’’ including safe for infants,
young children, and other sensitive subpopulations. The law places primary emphasis
on safety, leaving the EPA much less room to trade off health protection against the
economic benefits of pesticide use.
What is meant by ‘‘safe?’’ The FQPA, as we have seen, defines it as ‘‘reasonable cer-
tainty of no harm’’ to public health. In practice, scientists seeking to define safe levels
of exposure to chemicals generally rely on toxicity data from animal tests and incor-
porate a ‘‘safety margin’’ to take into account the scientific uncertainties involved.
Using this approach, the EPA, with peer review by the outside scientific community,
establishes a ‘‘reference dose,’’ or RfD for each pesticide. The RfD, measured in milli-
grams of chemical per kilogram of body weight per day, defines a dose level that is
thought to be without appreciable risk to human health, that is, a ‘‘safe’’ intake.80 | Pesticides