United States
Environmental Protection
Agency
Environmental Research
Laboratory
Gulf Breeze FL 32561
Research and Development
EPA-600/S3-83-021 June 1983
Project  Summary
Effects  of  Drilling  Fluids  on
Embryo  Development
Richard B. Crawford
  Toxicity of used drilling fluids to
embryo development was investigated
to ascertain the limits of safe usage of
these fluids in marine environments.
Embryos used as test systems were of
theteleost Fundulus heteroclitus. and
four echinoderms Echinarachnius par-
ma. Strongylocentrotus purpuratus.
Lytechinus p/ctus, and Lytechinus
variegatus. Gametes were collected in
season and combined for fertilization;
the resultant embryos were reared in
various concentrations of the drilling
fluids.   Any departure from normal
developmental patterns was noted and
the embryotoxicity for each flu id deter-
mined. The drilling fluids tested came
from various sources; 24 different sam-
ples were evaluated In addition, several
commercial drilling fluid components
were  examined in  the test systems
including a synthetic reference mud.
  These studies demonstrated that no
single drilling fluid is "typical" and that
the quantitative effects  on embryos
vary considerably from one fluid to
another. Some drilling fluids are quite
toxic to one or more of the embryo
systems, requiring  dilutions  of  over
10s to become "safe."  Others are
relatively innocuous, requiring very little
dilution to achieve a concentration in
which  embryo development can pro-
ceed normally.  Also, the effects on
development show variation from one
fluid to another, thus indicating that a
variety of components or compounds
are responsible for toxic manifestations.
Identification of the components re-
sponsible fortoxicity must await chemi-
cal analysis of these fluids.
  This Project Summary was developed
by EPA's Environmental Research La-
boratory, Gulf Breeze.  FL,  to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).

Introduction
  As a result of offshore petroleum drilling,
large quantities of drilling fluids (muds)
are  introduced into the marine  environ-
ment  These drilling fluids are aqueous
suspensions of a variety of components
pumped down the center of the drill bit.
The composition of such fluids varies with
the needs of the drilling operation, such as
lubrication, cooling, prevention of intrusion
of seawater into the bore hole, antibacterial
action, suspension of drill cuttings, and
capture of H2S. The drilling fluid may be
partially or wholly  discharged  into the
surrounding waters during drilling, espec-
ially at its completion. This discharge can
amount to significantly large quantities in
the vicinity of a drilling platform.
  The impact of drilling fluids on marine
and estuarine environments has been
largely unknown  due to  the paucity of
toxicological studies.   Recently, a few
studies on biological parameters affected
by drilling fluids have been reported. Ef-
fects on the chemosensory neurons in the
walking legs  of the lobster  have  been
examined. The impact of drilling fluids on
the  distribution of organisms in benthic
communities has been measured. Several
marine invertebrates,  as  well as some
teleosts, have been tested for their survival
in dilutions of drilling fluids. In each case,
some drilling fluids at appropriate concen-
trations have been shown to have adverse
effects on the biological model.
  The studies reported here were carried •
out to examine in some detail the effect of
several representative drilling fluids on
fertilization and embryo development For
model systems, embryos of an estuarine
teleost Fundulus heteroclitus, were chosen

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as well as embryos of four echinoderms,
Echinarachnius parma, Strongylocentrotus
purpuratus, Lytechinus pictus, and Lyte-
chinus variegatus.   These models rep-
resent a variety of habitats and embryo
types which would be found in the vicinity
of petroleum drilling operations. In addition,
each  of these species represents an im-
portant member of food chains. Conditions
which might interfere with the reproductive
capacity of the species would have effects
more far reaching than simply on the
species alone.

Design of  Experiments
  Models for the study of effects on em-
bryogenesis must be easily obtained and
easily reared in the laboratory. Also, they
should  represent  species found  in the
locale of interest Furthermore, it is helpful
if the species has been extensively studied
so that conditions for  its use may be
anticipated. All these criteria were met by
the species used in these studies.
  Because Fundulus eggs and sperm were
obtained in season, the time of fertilization
could be controlled. Within one minute of
fertilization, the zygotes were placed in
various  seawater dilutions of the drilling
fluids. The embryos developed in those
fluids until a few days past hatching (35
days)  and the various aspects of develop-
ment were observed daily.  Any departure
from observed normal development was
considered a measure of the toxicity of the
drilling fluid.
  Sand  dollar  and sea  urchin  gametes
were obtained in season by intracoelomic
injection of KC1. Within  15 minutes after
fertilization, the embryos were placed in
the drilling fluid solutions and develop-
ment was observed.  Rearing these em-
bryos through the pluteus stage takes
about four days and therefore  an assay
may be accomplished quite quickly.  In
addition, the  gametes may be  pre-incu-
bated in drilling fluid solutions to test the
effects of these substances on fertilization.
  Drilling fluids of various types and from
scattered regions were obtained from the
Environmental Research Laboratory of the
United  States  Environmental Protection
Agency, Gulf Breeze, Florida. These fluids
were stored at 4°C and, when dilutions
were made for testing,  were kept at the
temperature  used  for  rearing  the em-
bryos. Commercial components of drilling
fluids were also obtained from the U.S.
EPA and were tested for their toxicity.
  Drilling fluid test solutions were  stan-
dardized according to dry weight  Since
the dry weights of the fluids showed great
variation (from 1 300 mg/ml to 135 mg/
ml) different amounts of dilution were
required  to  achieve  the  standard  stock
suspension  of  10  parts  per thousand
(ppt).  This suspension was stirred for 1
hour and then filtered through Whatman
#1 paper. Further dilutions were made by
diluting the 10 ppt stock with filtered sea-
water.

Results
  Fundulus development was not affected
by any of the drilling fluids during early
stages.  At  the onset of organogenesis,
some fluids  caused a diminution of heart
beat rate at 10 ppt  The most significant
effect was on hatching and on coordination
of swimming of the fry. Adverse effects on
these activities could be achieved at con-
centrations of 1 ppt with some fluids.
  Echinoderm egg fertilization was pre-
vented by most drilling fluids at concentra-
tions of 10  ppt  Many of the fluids also
significantly reduced the fertilization rate
at 1 ppt  Some of the components were
effective  against fertilization at 10 parts
per million (ppm), especially those contain-
ing lignosulfonates or detergents.
  Development of the echinoderm em-
bryo was the most sensitive test with
these drilling fluids;  adverse effects were
observed in  some cases at 100 ppm and
10 ppm.  Developmental arrest or distor-
tions occurred at a variety of stages, de-
pending  on the fluid tested.   Also,  the
commercial drilling fluid components, es-
pecially those containing lignosulfonates
or detergents, inhibited development at
low concentrations.
  From the data  it  is clear that drilling
fluids vary to a considerable extent regard-
ing their toxicity.  By calculating actual
dilutions of the fluids required to achieve
toxic manifestations, "safe" dilutions, or
concentrations of the drilling fluids which
yield no  adverse effects in  these assay
systems, can be determined.  Such "safe"
dilutions range from 135 to 1,132,000
(least toxic to most toxic).  That is, one of
the fluids must be diluted about  one-
million-fold to allow normal development
of one of the sea urchins.  On the other
hand, another fluid is "safe"  by diluting it
slightly more than one-hundred-fold.

Conclusions
  Clearly, drilling fluids contain toxic ma-
terials, substances  which interfere with
fertilization and normal development It is
also clear that no one fluid is typical. Since
the range of toxicity varies  greatly from
one fluid to another, it  is not  always
possible  to prejudge the effect on marine
life of  a  large discharge of drilling fluids
from a drilling rig; each fluid must be
tested, or an accurate  log  kept of the
makeup  of the fluid compared with log
data from previously tested  fluids.  Even
with such logs, the effects of cuttings from
the bore hole on the toxicity of the fluid
would  not be known.
  Further, accurate  determinations of the
actual  dilutions of  discharges from rigs
must be known.  If a dilution of one million
fold were easily obtained a short distance
from a rig, it would seem that the  most
toxic drilling fluid is harmless to the animal
systems  tested  in  these studies.   Also,
more data are needed about chemical or
physical  changes in the drilling fluid that
might  render it more or less toxic in
seawater over a  given period of time.
  Comparison of chemical  analyses of
these drilling fluids with their toxicities
may yield interesting  and useful conclu-
sions regarding those components which
are harmful.
   Richard B. Crawford is with Trinity College, Hartford. CT061O6.
   Thomas W. Duke is the EPA Project Officer (see below).
   The complete report, entitled "Effects of Drilling Fluids on Embryo Development,"
     (Order No. PB 83-190 983; Cost: $8.50, subject to change) will be available only
     from:
           National Technical Information Service
           5285 Port Royal Road
           Springfield, VA  22161
           Telephone: 703-487-4650
   The EPA Project Officer  can be contacted at:
           Environmental Research Laboratory
           U.S. Environmental Protection Agency
           Sabine Island
           Gulf Breeze, FL 32561

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