E X T O X N E T
Extension Toxicology Network
A Pesticide Information Project of Cooperative Extension Offices of
Cornell University, Michigan State University, Oregon State University, and
University of California at Davis. Major support and funding was provided
by the USDA/Extension Service/National Agricultural Pesticide Impact
Publication Date: 9/93
TRADE OR OTHER NAMES
Trade names for products containing dienochlor include Pentac WP and
Pentac Aquaflow. The compound may be found in formulations with a wide
variety of other common pesticides.
Dienochlor is an organochlorine insecticide with contact action. It is
used for the control of plant damaging mites on a variety of ornamental
shrubs and trees outdoors and in greenhouses. The compound may also be used
on non-food ornamental crops. Dienochlor disrupts the egg laying ability
(oviposition) of female mites.
Dienochlor is a General Use Pesticide.
Products containing dienochlor are highly toxic when inhaled and thus
require the signal word WARNING on the label.
Symptoms of acute dienochlor exposure are similar to those of other
organochlorine compounds and may include, stimulation of the central nervous
system (tremors, convulsions, agitation and nervousness), slowing of
breathing, nausea, vomiting and diarrhea (1).
The oral LD50 for technical dienochlor is greater than 3,160 mg/kg in
male rats (2) indicating that the compound is only slightly toxic by this
route of exposure. The oral LD50 for a lower concentration of the compound
(38% ranges from 5,100 mg/kg to 20,000 mg/kg in rats) is greater than 5,000
mg/kg in rabbits, and is 16,900 mg/kg in mice.
Dienochlor is only slightly toxic by exposure through the skin
(dermal). The LC50 for the compound is greater than 3,160 mg/kg in rabbits(3).
Acute inhalation studies with the product Pentac 50 WP indicate that the
compound is highly toxic by this route of exposure. The LC50 value for the
product ranged between 1.4 mg/l and 2.4 mg/l in rats (3).
Dienochlor is not a primary skin irritant or a skin sensitizer and is
only a mild eye irritant. Rabbits exposed to a single dose of the technical
product (dose undisclosed) experienced corneal opacity and irritation. The
condition abated completely within seven days (3).
Only two sub-chronic feeding studies were found. Both studies were
conducted over three month periods. One study established a no observable
effect level (NOEL) in rats of 6.3 mg/kg/day. Above this dosage the rats
experienced a reduction in body weight gain. The other study noted a no
effect level of 16 mg/kg for mice. At the next highest dose administered (64
mg/kg), the mice experienced increased mortality, inactivity, hunchbacked-
walk, decreased body weight gain, changes in blood and urine chemistry, and
altered organ weights.
Rats fed dienochlor in their diets over two weeks had no effects at or
below 5 mg/kg/day. The limited evidence indicates that there is a very close
threshold for chronic effects in mice. There is only a small difference in
the amount of dose between 16 and 64 mg/kg (in relation to the LD50) for the
species. The numerous chronic symptoms of dienochlor exposure indicate that
there may be a risk to humans exposed to low to moderate levels of the
compound over time.
No data on reproductive effects of dienochlor were found.
No birth defects appeared in the offspring of pregnant rats fed up to
50 mg/kg dienochlor in their food. Maternal toxic effects (unspecified) were
noted at doses of 17 mg/kg. The time of exposure for the two studies was not
At least eight separate tests evaluating the mutagenicity of dienochlor
have produced mixed results. Test results have shown the compound to be non-
mutagenic or weakly mutagenic (3). This suggests that the mutagenic risk to
humans would be minimal.
No information was available on any cancer related effects from
The results from a single study indicated that the spleen and thymus
showed evidence of atrophy. The report summary compiled by the EPA also
indicated altered organ weights. The effects were noted at a dose of 64
mg/kg/day. The specifics of the change or the organs affected were not noted
Fate in Humans and Animals
Female rats fed a single, low dose (1 mg/kg) of dienochlor excreted
nearly ninety percent of the breakdown products of the compound in the feces
and only two percent in the urine (4). Nearly all of the dienochlor was
broken down in the rats within one day. The compound is poorly absorbed
through the stomach and intestines. At this dose after four days, only two
percent of the initial dose remained in the rat in the liver, kidneys, stomach
and intestines. Absorption of the compound is very slow. This may account
for its low oral toxicity (high oral LD50).
When the compound was administered on the skin of the rats only a very
small amount passed through the skin to the blood stream (2%) (4). The
authors indicated that even less would penetrate the skin of humans. Only
one percent of the applied dose was detected in the urine and less than 0.2
percent in the tissues.
Dienochlor is practically non-toxic to bobwhite quail and to mallard
ducks. The LD50 for the compound in the quail is 705 mg/kg and the LC50 for
dienochlor in mallards is nearly 4,000 mg/kg diet. A study with Japanese
quail produced an LD50 of 4,319 mg/kg but was deemed inadequate for several
reasons by the EPA (6). No other studies with birds were found. The effect
of this organochlorine compound on avian reproduction remains unevaluated.
Tests with several species of fish have indicated that the compound is
highly to very highly toxic to this group of organisms. The LC50 for
dienochlor is 0.6 mg/l for bluegill sunfish and 0.05 mg/l for rainbow trout
(6). Dienochlor is only moderately toxic to the freshwater invertebrate
Daphnia magna. There are no data available on the potential of the compound
to accumulate in aquatic organisms.
The compound is practically non-toxic to bees (2).
There is very little information about the fate of the compound in the
environment. Few studies have been conducted in this area. One study
indicated that the compound is non-persistent (5). A non-persistent compound
only lasts in the environment from a few hours to up to twelve weeks.
Dienochlor is readily broken down by the action of sunlight (5).
|NOEL (rat): ||6.25 mg/kg/day
|Common Name: ||dienochlor
|CAS #: ||2227-17-0
|Chemical Name: ||decachlorobis(2,4-cyclopentadien-1-yl)
|Chemical class: ||organochlorine
|Chemical Use: ||miticide
|Solubility in water: ||practically insoluble in water
|Solubility in solvent: ||Slightly soluble in hot ethanol, acetone and cyclohexanone. Moderately soluble in benzene, xylene, and other aromatic hydrocarbons.
|Partition coefficient: ||1411-2011 (octanol/water)
|Melting Point: ||122-123 degrees C
|Vapor pressure: ||1.3 mPa at 25 degrees C
Sandoz Crop Protection Corporation
1300 E. Touhy Avenue
Des Plains, Il 60018
Review by Basic Manufacturer:
Comments solicited: June, 1993
Comments received: June, 1993
The Agrochemicals Handbook. 1991. The Royal Society of Chemistry.
The Farm Chemicals Handbook. 1992. Meister Publishing. Willoughby,
Dienochlor. Tox Oneliners. 1990. US Environmental Protection
Agency. Office of Pesticides/HED/SACB.
Quistad, G.B., K.M. Mulholland and W.S. Skinner. 1986. The Fate of
Dienochlor Administered Orally and Dermally to Rats. Toxicology and
Applied Pharmacology 85(2):215-220.
Quistad, G.B., and K.M. Mulholland. 1986. Photodegradation of
Dienochlor. Journal of Agricultural Food Chemistry. 31(3):621-624.
Dienochlor. Ecological Effects Branch. US Environmental Protection
Agency. Reviewed 12/15/81.