Pesticide & Toxic Chemical News


EPA Approves use of Bromoxynil on Cotton


May 14, 1998 
  
Reversing a controversial decision the agency made last December,
EPA this week approved the use of bromoxynil on transgenic cotton
and established permanent tolerances for the  herbicide  and  its
metabolite DBHA.  

EPA  Assistant  Administrator  Lynn Goldman had written to cotton
growers Dec.  24,  1997,  informing them  that  the  EPA  "cannot
extend  the  tolerance  for  bromoxynil on cotton during the 1998
growing season because of serious  concerns  about  developmental
risks  to infants and children.  In particular,  we are concerned
that the data show  significant  and  irreversible  human  health
effects," she wrote.  

The  agency  had earlier established a time-limited tolerance for
residues of bromoxynil and  its  metabolite  DBHA  on  transgenic
cotton on May 2, 1997.  That tolerance expired January 1.  

However, in January, Rhone-Poulenc Ag Company, which manufactures
bromoxynil, submitted new residue data and risk assessments using
Monte Carlo methodology to EPA, agency spokesperson Denise Kearns
told  Pesticide  &  Toxic  Chemical  News May 12.  "Based on that
information,  EPA concluded that use of bromoxynil on cotton does
meet EPA standards,"  she said, adding that "farmers will be able
to use it this spring."  "This is a highly  positive  development
for  the  nation's cotton growers,  who have clearly demonstrated
through visits,  calls and correspondence with the EPA that  they
want to use Buctril in combination with BXN varieties of cotton,"
Alan Reade, president and CEO of Rhone-Poulenc Ag, said May 8.  

During the past several months, members of Congress, the National
Cotton  Council,  individual  cotton growers and other groups had
urged EPA to use "sound science"  in reviewing Buctril use on BXN
cotton, the company said.  

Stoneville Pedigree Seed,  a subsidiary of Calgene,  which is now
owned by Monsanto, developed the "Buctril BXN System,"  a variety
of cotton which the company genetically engineered for resistance
to bromoxynil.  

"We  are  disappointed  in  the  decision because Bromoxynil is a
dangerous chemical, " Jane Rissler, a scientist with the Union of
Concerned Scientists,  said in  an  interview.   "Basically,  the
agency  is  not  acting out the Food Quality Protection Act as it
should .  It is accommodating the chemical industry  and  putting
the  public  at  risk."  One of the biggest concerns about cotton
genetically altered to be resistant to bromoxynil is that it  has
the  ability  to  break  down  the  herbicide  and accumulate the
metabolite DBHA within the plant,  USC scientists said.  DBHA  is
unique  to  the transgenic plant,  and no one has done the safety
testing needed on it,  Rissler said.  "Rhone-Poulenc and EPA  are
assuming that DBHA acts the same as bromoxynil,  but that data is
still not in,"  she said.  If DBHA is a more  powerful  chemical,
that  would  push  the  numbers  up in the risk calculation,  she
added.  

The aggregate cancer risk for the U.S.  population calculated for
use of bromoxynil is 1.7 x 10-6,"  EPA said in a May  13  Federal
Register notice.  "EPA has commonly referred to a negligible risk
as  one  that  is  at  or  below  1  in  1  million  (1  x 10-6).
Quantitative cancer risk assessment is  not  a  precise  science.
There  are  a  significant  number  of  uncertainties in both the
toxicology used to derive the cancer potency of a  substance  and
in  the  data used to measure and calculate exposure.  Thus,  EPA
generally  does  not  attach  great  significance  to   numerical
estimates that differ by approximately a factor of 2." 

Therefore,  EPA  concludes  "that there is a reasonable certainty
that no harm will result to  the  general  population  and  major
identifiable  population  subgroups  from  aggregate  exposure to
bromoxynil." 

The agency established tolerances  for  bromoxynil  and  DBHA  in
undelinted  cottonseed at 1.5 ppm,  cotton gin by-products at 7.0
ppm and cotton hulls at 5.0 ppm.  

In addition,  the agency established tolerances for  residues  of
bromoxynil  and DBHA,  resulting from the application of octanoic
acid and heptanoic acid esters of bromoxynil to cotton,  in or on
cattle, hogs, horses, goats and sheep to 0.5 ppm in meat, 3.5 ppm
and  1.0  ppm  in  fat,  the  Federal  Register  notice said.  In
addition, tolerances were established at 0.1 ppm in milk; at 0.05
ppm in eggs; at 0.05 ppm in poultry meat and fat;  and at 0.3 ppm
in poultry.  

EPA  noted  that  the  registration  of  bromoxynil will restrict
treatment of bromoxynil on cotton to no  more  than  1.3  million
acres during 1998.  

------  Kathleen  Hart  5-15-98 Bureau of National Affairs,  Inc.
Washington D.C