The Agrochemical and Pesticides Safety Handbook

323 Pages·1998·18.22 MB·English

by  Waxman

PART ONE
INTRODUCTION AND
RESOURCE MATERIALS
Michael F. Waxman
CHAPTER 1
INTRODUCTION
Pesticides are chemicals or biological substances used to kill or control
pests. They fall into three major classes: insecticides, fungicides, and herbi-
cides (or weed killers). There are also rodenticides (for control of vertebrate
pests), nematicides (to kill eelworms, etc.), molluscicides (to kill slugs and
snails), and acaricides (to kill mites). These chemicals are typically manmade
synthetic organic compounds, but there are exceptions which occur naturally
that are plant derivatives or naturally occurring inorganic minerals.
Pesticides may also be divided into two main types contact or nons-
ystemic pesticides and systemic pesticides. Contact or surface coating pesticides
do not appreciably penetrate plant tissue and are consequently not transported,
or translocated, within the plant vascular system. The earlier pesticides were
of this type; their disadvantages were that they are susceptible to the effects of
the weather and new plant growth was not protected.
In contrast, most of recently developed pesticides are systemically active
and therefore they penetrate the plant cuticle and move through the plant vas-
cular system. Examples of systemic fungicides are benomyl and hexacona-
zole. These systemic agents can not only protect a plant from attack but also
inhibit or cure established infections. They are not affected by weathering and
also confer immunity to all new plant growth.
The use of pesticides has been traced by historians to before 1000 B.C.
Homer mentioned the use of sulfur as a fumigant to avert disease and control
insects. Theophrastus, in 300 B.C., described many plant diseases known
today such as scorch, rot, scab, and rust. There are also several references in
the Old Testament to the plagues of Egypt for which the locust was chiefly
responsible, and even today locusts cause vast food losses in the Near East and
Africa. Pliny in 79 A.D. advocated the use of arsenic as an insecticide and by
900 A.D., the Chinese were using arsenic and other inorganic chemicals in
their gardens to kill insects.
In the seventeenth century the first naturally occurring insecticide, nico-
tine from extracts of tobacco leaves, was used to control the plum curculio and
the lace bug. Hamberg (1705) proposed mercuric chloride as a wood preserva-
tive and a hundred years later Prevost described the inhibition of smut spores
by copper sulfate.
It was not until the middle of the nineteenth century that systematic scien-
tific methods began to be applied to the problem of controlling agricultural
pests. About 1850 two important natural insecticides were developed: rote-
none from the roots of derris plants and pyrethrum from the flower heads of a
species of chrysanthemum. These insecticides are still widely used. At about
the same time, new inorganic materials were introduced forcombating insect
pests. For instance, an investigation into the use of new arsenic compounds
led in 1867 to the introduction of an impure copper arsenite (Paris Green) for
control of the Colorado beetle in the state of Mississippi. In 1892 lead arse-
nate was used for control of gypsy moth.
The Irish Potato Famine of the 1840s illustrates what can occur when a
staple food crop is stricken by a disease against which there is no known de-
fense. The potato crop was virtually destroyed by severe attacks of thefungal
disease known as potato late blight, resulting in the deaths of more than a
million people.
Millardet, in 1882, accidentally discovered a valuable chemical treatment
for the control of pathogenic fungi, like potato blight and vine mildew. This
discovery came from a local custom of the farmers in the Bordeaux district of
France. They daubed the roadside vines with a mixture of copper sulfate and
lime in order to discourage pilfering of the crop. At this time the crops of the
French vineyards were being destroyed by the downy mildew disease.
Millardet observed that although the vines away from the road were heavily
infested with mildew, those alongside the road which had been treated with the
mixture were relatively free from the disease. Millardet subsequently carried
out further experiments which established the effectiveness of the mixture of
copper sulfate, lime, and water against vine mildew. The mixture, called the
Bordeaux mixture, was widely applied, the disease was arrested, and Millardet
became somewhat of a hero.
In 1897 formaldehyde was introduced for the first time as a fumigant. In
1913 organomercurials were first used as fungicidal seed dressings against ce-
real smut and bunt diseases.
W. C. Piver in 1912 developed calcium arsenate as a replacement for Paris
Green and lead arsenate. This mixture soon became important for controlling
the boll weevil on cotton in the United States. By the early 1920s the
extensive application of arsenical insecticides caused widespread public outcries
because fruits and vegetables treated with arsenates were sometimes shown to
contain poisonous residues. This stimulated the search for other less
dangerous pesticides and led to the introduction of organic compounds, such as
tar, petroleum oils, and dinitro-o-cresol. The latter compound eventually
replaced tar oil for control of aphid eggs, and in 1933 was patented as a
selective herbicide against weeds in cereal crops. Unfortunately, this
Michael F. Waxman
is also a very poisonous substance.
The 1930s really represents the beginning of the modern era of synthetic
organic pesticides—important examples include the introduction of alkyl thio-
cyanate insecticides, the first organic fungicides (dithiocarbamate fungicides),
and a host of other fungicides and insecticides. In 1939 Müller discovered the
powerful insecticidal properties of dichlorodiphenyltrichloroethane or DDT. In
1943, DDT was first manufactured and soon became the most widely used
single insecticide in the world.
In the 1940s, many chlorinated hydrocarbon insecticides were developed
though they did not come into widespread use until the 1950s. Common
examples include aldrin, dieldrin, heptochlor, and endrin. However, in spite of
their early promise, these organochlorine insecticides are now much less used
because of their environmental pollution impact.
The organophosphosphates represent another extremely important class of
organic insecticides. They were developed during World War II as chemical
warfare agents. Early examples included the powerful insecticide schradan, a
systemic insecticide, and the contact insecticide parathion. Unfortunately,
both of these compounds are highly poisonous to mammals and subsequent
research in this field has been directed toward the development of more
selective and less poisonous insecticides. In 1950, malathion, the first
example of a wide-spectrum organophosphorus insecticide combined with very
low mammalian toxicity, was developed. And at about the same time the
phenoxyacetic acid herbicides were discovered. These systemic compounds are
extremely valuable for the selective control of broad-leaved weeds in cereal
crops. These compounds have a relatively low toxicity to mammals and are
therefore relatively safe to use.
The bipyridinium herbicides were introduced in 1958. These are very
quick-acting herbicides which are absorbed by the plants and translocated
causing desiccation of the foliage. These herbicides are strongly absorbed to
the clay components of the soil and become effectively inactivated.
It was not until the late 1960s that effective systemic fungicides appeared
on the market, and their development represents an important breakthrough in
the field of plant chemotherapy. The major classes of systemic fungicides
developed since 1966 are oxathiins, benzimidazoles, thiophanates, and
pyrimidines. Other effective systemic fungicides used currently include
antibiotics, morpholines, organophosphorus compounds, and most recently,
the sterol biosynthesis inhibitors, e.g., triazoles.
Throughout the history of pesticide usage, the manufacturers of pesticides
have faced the same challenge that confronts the makers of pesticides today.
That is, the development of chemicals that kill or control unwanted insects,
weeds, fungi, rodents and other pests without harming desired plants,
beneficial insects, wildlife, and, most important, humans.
Chemicals that control rats are termed rodenticides. The first effective
compound was warfarin. It was developed by the Wisconsin Alumni Research
Foundation in 1944. It functions as an anticoagulant in human medicine.
However, when used against rats and mice, at high concentrations it is
extremely effective, causing death by internal hemorrhaging.
In 1962 The Silent Spring, written by Rachel Carson, was published.
Carson’s book was one of the first that attracted national attention to the
problems of toxic chemicals and the effects of these chemicals on the
environment. The Silent Spring recounted how the residues of the pesticide
DDT could be found throughout the food chain. In aquatic birds, high levels
of DDT were associated with reduced fertility. DDT affected the deposition of
calcium in avian ovaries, leading to egg shells too thin to survive, thus
causing a widespread reduction in many bird species.
The Silent Spring and other books on the dangers of pesticides have served
to illustrate that great efforts must be taken to prevent the misuse of pesticides
and other chemicals. It is this misuse, overuse, and improper disposal that
causes many of the problems that have been reported.
Recently, man has made great advances in the genetic manipulation of
genes. It is now possible to create in the laboratory seeds and thus crops
which possess the genetic ability to kill or inhibit disease-causing pests.
The term “agrochemical” is broader and includes chemicals which will
enhance the growth and yield of crops, but excludes large-scale inorganic
fertilizers.
I. THE MARKET FOR PESTICIDES
A. CURRENT STATUS
In 1992, approximately $8.2 billion, and in 1993, approximately $8.5
billion worth of pesticides were purchased for use in the United States. There
is no question that the productivity of American agriculture is due in large part
to the success of modern pesticides. There is also no question that we are still
grappling with the problem of balancing the usefulness of pesticides with their
safety.
The largest market for pesticides as of 1993 was the United States. It
represents 34% of the total world market, which has been estimated at over
$25 billion. The retail value of pesticide sales in the United States for 1993
was well over $8 billion (see Table 1.1 and Figures 1.1 and 1.2).
Michael F. Waxman
Table 1.1. U.S. and World Conventional Pesticide Sales at User Level, 1993
Estimates.
U.S. % of
Pesticide Class U.S. Market World Market World Market
Million % Million %
User E x penditures i n M i llions o f $
Herbicides $4,756 56% $11,700 46% 41%
Insecticides 2,550 30% 7,900 31% 32%
Fungicides 584 7% 4,139 16% 14%
Other 594 7% 1,550 6% 38%
Total $8,484 100% $25,280 100% 34%
Volume o f A c tive I n gredients i n M i llions o f l bs
Herbicides 620 57% 2,110 47% 29%
Insecticides 247 23% 1,625 36% 15%
Fungicides 131 12% 535 12% 24%
Other 83 8% 230 5% 36%
Total 1,081 100% 4,500 100% 24%
Note: Totals may not add due to rounding.
Source: EPA estimates based on National Agricultural Chemicals Association.
4500
4000
U.S. Market
3500
World Market
3000
2500
2000
1500
1000
500
0
Herb. Insect. Fungi. Other Total
Figure 1.1. U.S. vs. World Conventional Pesticide Sales: Volume of
Active Ingredient, 1993.
Pesticide usage in the U.S. has been relatively stable at about 1.1 billion
pounds of active ingredient during recent years. The agricultural share of pes-
ticide usage (see Table 1.2) appears to have stabilized at about three-fourths of
the total after increasing steadily throughout the 1960s and 1970s, primarily
due to the expanded use of herbicides in crop production. Growth in the use of
$30,000
U.S.Market
$25,000
WorldMarket
$20,000
$15,000
$10,000
$5,000
$0
Herb. Insect. Fungi. Other Total
Figure 1.2 U.S. vs. World Conventional Pesticide Sales: User
Expenditures, 1993.
Table 1.2 United States Conventional Pesticide Usage, Total and Estimated
Agricultural Sector, 1964-1993.
Year Total U.S. Agricultural Sector
Millions of lbs. Active Ingredient Percent of Total
1964 540 320 59%
1965 610 335 55%
1966 680 350 51%
1967 735 380 52%
1968 835 470 56%
1969 775 430 55%
1970 740 430 58%
1971 835 495 59%
1972 875 525 60%
1973 910 560 62%
1974 950 590 62%
1975 990 625 63%
1976 1,030 660 64%
1977 1,075 720 67%
1978 1,110 780 70%
1979 1,058 840 79%
1980 1,075 846 79%
1981 1,101 860 78%
1982 1,056 815 77%
1983 963 733 76%
1984 1,080 850 79%
1985 1,112 861 77%
1986 1,096 820 75%
1987 1,087 814 75%
1988 1,130 845 75%
1989 1,070 806 75%
1990 1,086 834 77%
1991 1,077 817 76%
1992 1,103 839 76%
1993 1,081 811 75%
* Active ingredient
Note: Excludes wood preservatives and disinfectants.
Source: EPA estimates.
Michael F. Waxman
pesticides has been slowed by lower application rates due to the introduction of
more potent pesticides, more efficient use of pesticides, and lower farm com-
modity prices. USDA and EPA are working together with commodity groups
to develop plans to reduce use/risk of pesticides as part of a food safety initia-
tive.
The volume of pesticides used for non-agricultural purposes in the U.S.
also has been quite stable in recent years at about 275 million pounds of active
ingredient (a.i.). This equals about 1.1 pounds per capita in the U.S. (average
for 250 million people). Considering all usage, including agricultural, U.S.
pesticide usage equals somewhat more than 4 pounds per capita (4.2 pounds in
1993).
Table 1.3 shows that in the United States there are more than 120
manufacturers of pesticides, with only 20 accounting for the bulk of
production and sales. The manufacturers supply the pesticidal active
ingredients (not including carrier liquids, diluting agents and inert ingredients
found in formulations) to over 2,000 pesticide formulators who mix the active
and inactive ingredients to produce over 21,000 registered products. As of
1993, there were about 17,000 distributor-dealers of pesticides, approximately
40,000 pest control firms, almost a million certified private applicators
(individual growers), and over 350,000 certified commercial applicators. As of
1994, there was an estimated 17,500 licensed-certified agricultural pest control
advisors, of whom over 8,000 were self-employed independent consultants.
Table 1.3 U.S. Pesticide Production, Marketing and User Sectors; Profile of
Number of Units Involved, 1993/1994 Estimates (Approximate Values).
PRODUCTION AND DISTRIBUTION
Basic Production
1. Major Basic Producers 20
2. Other Producers 100
3. Active Ingredients Registered 860
4. Active Ingredients with Food/Feed Tolerances 453
5. Chemical Cases for Re-registration
—Pre-FIFRA 1988 612
—Post-FIFRA 1988 405
6. New Active Ingredients Registered
—1992 11
—1993 20
7. Total Employment 6,000-10,000
8. Producing Establishments 7,300
Distribution and Marketing
1. Formulators
—Major national 150-200
—Other 2,000
Table 1.3 continued
2. Distributors and Establishments
—Major national 250-350
—Other 16,900
3. Formulated Products Registered 21,560
—Federal level 18,360
—State 3,200
USER LEVEL
Agriculture Sector
1. Land in Farms 991M acres
2. Harvested 289M acres
3. Total No. Farms 2.1M
4. No. of Farms Using Chemicals for:
—Insect on hay crops 554,000
—Nematodes 66.000
—Diseases on crops/orchards 129,000
—Weed/grass/bush 913,000
—Defoliation/fruit thinning 75,000
(Above are 1987 census numbers)
5. No. Private Pesticide Applicators Registered 965,700
Industrial/Commercial/Government Sector
1. No. Commercial Pest Control Firms 35,000-40,000
2. No. Certified Commercial Applicators 351,600
Home & Garden Sector
1. Total U.S. Households 94M
2. No. Households Using (’90)
—Insecticides 52M
—Fungicides 36M
—Herbicides 14M
—Repellents 17M
—Disinfectants 40M
—Any pesticides 69M
Source: EPA estimates.
In the United States in 1993, 75 percent of the pesticides sold are used in
agriculture. Government and industry uses 18 percent, and home and garden
consumption accounts for the remaining 7 percent. Industrial and commercial
users consist of pest control operators, turf and sod producers, floral and scrub
nurseries, railroads, highways, utility rights-of-way, and industrial plant site
landscape management (see Table 1.4 and Figure 1.3).
Pesticides are regulated by the United States Environmental Protection
Agency (EPA). The number of active ingredients registered and in production
has declined in the last ten years, from over 1,200 active ingredients to 860 in
1993. Of these only 200 are considered major products and manufactured in
quantity (see Table 1.5). The table below shows a breakdown of the types of
pesticides and numbers in production according to the latest available statis-
tics.
Michael F. Waxman
Table 1.4 Volume of Conventional Pesticide Active Ingredient sUsed in the
U.S. by Class and Sector (Millions of lbs).
Herbicides Insecticides Fungicides Other Total
Sector lbs. % lbs. % lbs. % Lbs % lbs. %
1993
Agriculture 481 78 171 69 84 64 75 90 811 75
Ind./Comm./
Govt. 112 18 44 18 36 27 5 6 197 18
Home &
Garden 27 4 32 13 11 8 3 4 73 7
Total 620 100 247 100 131 100 83 100 1,081 100
Note: Totals may not add due to rounding.
Source: EPA estimates based on National Agricultural Chemicals Association.
500
450 Agriculture
400 Ind./Comm./Govt.
Home & Garden
350
300
250
200
150
100
50
0
Herb. Insect. Fung. Other Total
Figure 1.3 U.S. Volume for Conventional Pesticides, 1993 Estimates.
Table 1.5 Breakdown of Types of Pesticide in Production.
Type Nu mber
Disinfectants 200
Fungicides and Nematicides 165
Herbicides 240
Insecticides 215
Rodenticides 40
The most heavily used pesticides in the agricultural sector in 1993 are
listed in Table 1.6. Of these, 17 are herbicides, 3 are insecticides and 5 are
fungicides. Table 1.7 lists the most commonly used pesticides in the non-
agricultural sectors.