NOV  71990
             INTERNAL FACT  SHEET ON  DACTHAL
Description
     Dacthal is a preemergent herbicide registered for
use on turf (home lawns, sod farms, and golf courses),
gardens, and for commercial vegetable production on
onions, cole crops, greens, lettuce, sweet potatoes,
horseradish, radishes, watermelons, beans, corn,
cantaloupes, cotton, cucumbers, eggplants, garlic,
onions, peppers, soybeans, squash, strawberries,
turnips, rutabagas, and other crops.  The pesticide is
one of the most widely used herbicides on home lawns
for the control of crabgrass.

     Dacthal was first registered in 1958.  As of April
1990, there were 96 products registered to 44
registrants.  The sole manufacturer is the  Fermenta
Plant Protection Company  (formerly SDS Biotech Corp).
     In 1985,  3 to 4 million pounds of Dacthal were
used nationally, of which 1.0 to 1.5 million pounds
were for agricultural crops.  Since 1986, the use of
Dacthal on turf has declined significantly as a result
of increased competition from other products.  The most
recent estimate of total usage for dacthai (1988 data)
is 2.25 million pounds on about 275,000 acres.  Use on
turf is now about one-fourth of total use: it is
estimated that homeowners treat about 15,000 acres of
lawns, and Dacthal is applied to about 40-45,000 acres
of commercial sod farms and  golf courses.  Turf uses
represent about 580,000 pounds of active ingredient
annually.  Dacthal is frequently used on turf in the
eastern and central United States but much more rarely
used in western states.  However, for agricultural use,
60% of Dacthal is used in California, Arizona, and
Washington State.

    For agricultural and turf uses, Dacthal has high
application rates — single applications may be as high
as 15 pounds per acre although 10 pounds per acre is
more typical in turf applications.

Concerns about TCDD and HCB in Dacthal

     The Agency has been concerned about potential
health risks posed by the small amounts of two
contaminants, HCB (hexachlorobenzene) and TCDD

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(dioxin), that result from the manufacturing process of
Dacthal. The Agency has also reviewed data available
on Dacthal itself, and found that a significant number
of data gaps for this compound. The registrant is
required to submit studies to fill these data gaps as
part of EPA’S program to “reregister” all older
pesticides. All required data should be submitted to
EPA by late 1992, and a reregistration decision should
be made in 1993.
Concern has focused on the TCDD and HCB
contaminants of Dacthal, because both compounds have
been classified as probable human carcinogens. TCDD
has also been linked to birth defects and other
reproductive hazards, a condition known as chloracne,
and to immune system effects. HCB has been shown to
cause adverse reproductive effects in rats.
EPA announced in 1985 that the registrant was
required to remove the “trace elements” of TCDD from
Dacthal “if technically feasible.” The manufacturer
began to voluntarily withhold products containing TCDD
at levels greater than 0.1 parts per billion (ppb).
The manufacturer subsequently informed EPA that TCDD
levels in their products do not exceed 0.01 ppb. and
that the levels of HCB do not exceed 0.3 percent.
As part of the reregistration review in 1988,
Dacthal was considered for Special Review because of
concerns about both TCDD and HCB contaminants in
Dacthal products. The Agency estimated the potential
health risks from both dietary and non-dietary
exposures to the Dacthal contaminants, and concluded
that the risks were low and did not warrant a Special
Review. However, it was also noted that further
toxicity and exposure data on Dacthal were pending, and
that EPA could not definitively assess the potential
risks without such data.
Current Status
EPA has recently (October 1990) received
additional data that will clarify the human exposure
associated with turf and lawn care uses of Dacthal.
This data is now under review to determine whether it
indicates any change from earlier risk assessments that
would warrant regulatory action.
Recent findings of Dacthal residues in drinking
water wells in EPA’S National Pesticide Survey are
reported to be well below EPA Health Advisory levels.
Thus, it is not likely that these findings would

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substantially alter risk estimates for Dacthal
contaminants. The cause of Dacthal and HCB detections
in drinking water wells will be evaluated as part of
the Phase II analysis of the National Pesticide Survey
project.
Dacthal is on EPA’S “List A” for reregistration,
which includes pesticides that are a high priority for
reregistration. Because the existing data base had
many data gaps, EPA has required many environmental
fate, exposure, and toxicology studies to be performed
by the registrant. The Agency will have received all
data and will be ready to make a decision on the
pesticide by Fiscal Year 1993. However, if new
information indicates that the pesticide may be posing
unreasonable risks of adverse effects to public health
or the environment, the Agency will take appropriate
action.

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