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#250 - Pet Dogs Get Cancer From Weed Killers, 10-Sep-1991

Pet dogs exposed to the weed killer 2,4-D are dying of cancer at twice
normal rates, according to a study just published in the JOURNAL OF THE
NATIONAL CANCER INSTITUTE.[1] Dog owners who spray or dust their lawns
with weed killers containing 2,4-D are doubling Fido's chances of
getting cancer, the study shows. Dogs walk across, or roll in,
herbicide-treated lawns and then ingest toxic chemicals when they lick
their coats or paws. Popular lawn-care products containing 2,4-D
include Weedone, Weed-B-Gone, and many others (see below).[2]

Naturally, children who play on treated lawns will also come in contact
with the chemical; dogs and children can also track the chemical
indoors where prolonged exposure to humans may occur, but, so far as we
know, no one has yet studied effects of weed killers on children or
other family members inhabiting treated home sites.

In the past decade, several studies of farmers, and a few of railroad
workers, have shown a connection between exposure to 2,4-D and an
increased risk of human cancers. This latest study shows that dogs get
some of the same kinds of cancers from weed killers that farmers in
Nebraska,[3] Kansas,4 and Saskatchewan,5 and workers in Sweden[6],7,8
are reported to get from using 2,4-D on crops and to clear weeds along
railroad tracks. In humans, the cancers are known as soft tissue
sarcomas (STS), malignant lymphomas, and non-Hodgkin's lymphomas. In
dogs, malignant lymphomas and non-Hodgkin's lymphomas predominate. The
occurrence of such cancers in the American people has been rising
slowly but steadily for several decades, tracking the emergence of the
modern life style in which the dandelion-free lawn has come to
symbolize the good life.[9] Non-Hodgkin's lymphomas--the kind dogs are
reported to get most often from exposure to 2,4-D--have been the second
fastest-growing cancer in humans in the U.S. during the past 15 years.

It is not clear exactly which components of weed killers are
responsible for the cancers. There are three possible sources of the
problem: (a) the active ingredient in the weed killer, (b) the so-
called "inert" ingredients that are used as carriers for the chemicals
that actually kill weeds, and (c) the dioxins that contaminate the
active ingredients during manufacture.

About 600 million pounds of 2,4-D are spread on American soil each year
by homeowners and farmers--about 60 million pounds of "active
ingredients" and about 540 million pounds of "inert" ingredients that
can include carbon tetrachloride (a carcinogen), chloroform (a
carcinogen), chloroethane (a carcinogen) and 20 or more other
ingredients that are labeled "inert" but which have well-known toxic
properties.[10] Federal pesticide law does not require chemical
companies to disclose what is in the "inert" ingredients in their
products. Furthermore, federal law provides a $10,000 penalty for any
government employee who reveals the make-up of "inert" ingredients in

2,4-D and its closely-related chemical cousin, 2,4,5-T (which is now
banned in the U.S.), are contaminated with dioxins during manufacture.
Dioxins are extremely potent toxins that have a wide spectrum of
effects in humans, wildlife, and laboratory animals (ses RHWN #249). A
recent study by the National Institutes of Occupational Safety and
Health (NIOSH) revealed a 46% cancer increase among workers in
factories manufacturing these weed killers. (See RHWN #219.) Previous
studies by scientists employed by herbicide manufacturing companies
(BASF and Monsanto) had purported to show no effects in workers but
there is now a growing concern among government officials that some of
these studies were falsified.[11]

People spread 2,4-D around their homes and gardens to kill broad-leaf
weeds, crab grass and dandelions. Farmers use it on tomatoes to cause
all fruits to ripen at the same time for

machine harvesting, and to increase the red color in potatoes. Utility
companies, highway departments, and railroads use it to clear brush
beneath power transmission lines and along highways and tracks. It is
used heavily on corn, sorghum, rice and other crops to keep weeds down.
From 1962 to 1971 during the Vietnam War, 2,4-D and its chemical cousin
2,4,5-T mixed together formed Agent Orange; it was sprayed by soldiers
and airmen to defoliate the jungle where the Vietcong were living.
Thousands of GIs have filed lawsuits against the U.S. government and
against individual companies that supplied components of Agent Orange,
such as Monsanto, Dow, Uniroyal, Hercules, Diamond Shamrock and others.
A recent study in the AMERICAN JOURNAL OF PUBLIC HEALTH reveals that
Vietnam veterans are 70% more likely to father children with one or
more major birth defects, compared to men with no military service; it
is unclear whether herbicide exposure is the most important cause.[12]

Common names for weed killers containing 2,4-D include Weedone, Weed-B-
Gon, Green Cross Weed No More 80, Lawn-Keep, Salvo, Red Devil Dry Weed
Killer, De-Pester Ded-Weed, Plantgard, Dormon, Dormone, Brush Killer
64, Weed-Rhap, Bladex-B, Butoxy-D, Dicofur, Ipaner, Moxon, Netagrone,
Pielik, U 46 DP, Verton 38, B-Selektonon, Silvaprop, Agricorn D, Acme
LV 4, Acme LV 6, Coprider, D50, DMA 4, Emulsamine, Fernesta, Ferxone,
Macondray, Pennamine, Tributon, Weedatul, Agroxone, Spritz-Hormin,
Desormone, Decamine, Weedar, R-H Weed Rhap 20, and Scott's 4-XD Weed

--Peter Montague


[1] Howard M. Hayes and others, "Case-Control Study of Canine Malignant
Lymphoma: Positive Association With Dog Owner's Use of 2,4-
Dichlorophenoxyacetic Acid Herbicides," JOURNAL OF THE NATIONAL CANCER
INSTITUTE Vol. 83 (Sept. 4, 1991), pgs. 1226-1231.

[2] Product names were gathered from a search on "2,4-D" in the
National Library of Medicine's online Hazardous Substances Data Bank;
to learn details of this online system, write National Library of
Medicine, 8600 Rockville Pike, Bethesda, MD 20894.

[3] Shelia Hoar Zahm and others, "A Case-Control Study of Non-Hodgkin's
Lymphoma and the Herbicide 2,4-Dichlorophenoxyacetic Acid (2,4-D) in
Eastern Nebraska," EPIDEMIOLOGY Vol. 1 (September, 1990), pgs. 349-256.

[4] Shelia K. Hoar and others, "Agricultural Herbicide Use and Risk of
Lymphoma and Soft-Tissue Sarcoma," JOURNAL OF THE AMERICAN MEDICAL
ASSOCIATION Vol. 256 (Sept. 5, 1986), pgs. 1141-1147; see RHWN #3.

[5] A. Blair, "Herbicides and non-Hodgkin's lymphoma: New evidence from
a study of Saskatchewan farmers," JOURNAL OF THE NATIONAL CANCER
INSTITUTE Vol. 82 (1990), pgs. 544-545.

[6] Olav Axelson and others, "Herbicide Exposure and Tumor Mortality,"
1980), pgs. 73-79.

[7] Mikael Eriksson and others, "Exposure to Dioxins as a Risk Factor
for Soft Tissue Sarcoma: A Population-Based Case-Control Study,"

[8] Lennart Hardell and Mikael Eriksson, "The Association Between Soft
Tissue Sarcomas and Exposure to Phenoxyacetic Acids," CANCER Vol. 62
(Aug. 1, 1988), pgs. 652-656.

[9] Kenneth P. Cantor and Others, "Distribution of Non-Hodgkin's
Lymphomas in the United States Between 1950 and 1975," CANCER RESEARCH
Vol. 40 (August, 1980), pgs. 2645-2652.

[10] U.S. Environmental Protection Agency staff members estimate that
use of 2,4-D "active ingredient" is between 57 and 62 million pounds
per year. Federal law does not allow EPA officials to gather exact
(Washington, DC: Economic Analysis Branch, Biological and Economic
Analysis Division, Office of Pesticide Programs, [U.S.] Environmental
Protection Agency, September 1988), Table 9. However "active
ingredients" account for only about 10% of an herbicide like 2,4-D; see
Susan Jaffe, Michael Surgan, and Timothy P. Urban, THE SECRET HAZARDS
OF PESTICIDES: INERT INGREDIENTS (Albany, NY: Office of the Attorney
General, June, 1991), Table 1. Free copies of this Attorney General's
report are available through the mail by contacting Office of Public
Information, NY State Department of Law, 120 Broadway, NY, NY 10271.
You can try to place a phone order by calling (212) 341-2000.

[11] See, for example, Leslie Roberts, "Monsanto Studies Under Fire,"
SCIENCE Vol. 251 (February 8, 1991), pg. 626. A Monsanto public
relations spokesperson says the company's studies of worker health were
sound; nevertheless, Roberts reports, U.S. Environmental Protection
Agency has recently opened a criminal investigation to determine
whether Monsanto "falsified" three epidemiological studies of its
workers. For further evidence of concern expressed by government
officials, see RHWN #171.

[12] Ann Aschengrau and Richard R. Monson, "Paternal Military Service
in Vietnam and the Risk of Late Adverse Pregnancy Outcomes," AMERICAN
JOURNAL OF PUBLIC HEALTH Vol. 80 (October, 1990), pgs. 1218-1224.

Descriptor terms: 2,4-d; cancer; dogs; inert ingredients; herbicides;
pesticides; farming; occupational safety and health; studies;