OT:Malathion

[Guest guest]

Following is NYCAP correspondence on the NYC malathion spraying, and some

information on malathion toxicology. Guiliani is pledging to continue

blanketing NYC until the first frost. News reports are describing

malathion as perfectly safe and there is much evidence to the contrary. I

have a large body of information on paper. I am sending what I have

readily available in e-mailable text. Please use these facts to raise

awareness about the dangers of malathion.

September 10, 1999

The Op-Ed Page

The New York Times

229 West 43rd Street

New York, NY 10036

Fax: 212-556-3690

To the Editor:

The New York Coalition for Alternatives to Pesticides (NYCAP) is alarmed

about the blanket spraying of the organophosphate insecticide, malathion in

NYC.

The news reports make it seem as if malathion is a harmless substance that

can be safely blanketed across the city. This is far from accurate.

According the USEPA, no pesticide can be labeled as safe, even if used as

directed. Pesticides are poisons that are designed to kill living things.

Malathion is a nerve poison that has been implicated in California as one

of the third most common causes of pesticide-related illness between

1981-85. To quote more current information from the Extention Toxicology

Network, which is funded through the USDA, Extension Service/National

Agricultural Pesticide Impact Assessment Program. " ...It has been reported

that single doses of malathion may affect immune system response [2].

Symptoms of acute exposure to organophosphate or cholinesterase-inhibiting

compounds may include the following: numbness, tingling sensations,

incoordination, headache, dizziness, tremor, nausea, abdominal cramps,

sweating, blurred vision, difficulty breathing or respiratory depression,

and slow heartbeat. Very high doses may result in unconsciousness,

incontinence, and convulsions or fatality...Numerous malathion poisoning

incidents have occurred among pesticide workers and small children through

accidental exposure. In one reported case of malathion poisoning, an infant

exhibited severe signs of cholinesterase inhibition after exposure to an

aerosol bomb containing 0.5% malathion [44]...Malathion is rapidly and

effectively absorbed by practically all routes including the

gastrointestinal tract, skin, mucous membranes, and lungs. "

While evidence suggests harmful effects occur in high doses, there is more

than enough evidence to warrant a precautionary approach. In light of the

fact that epidemiologists have not yet confirmed where the encephalitis

victims contracted the disease, spraying malathion widely throughout the

city, in our parks and where our children play is unwise and is not worth

the risk.

Total control of mosquito populations is impractical, and the widespread

use of poisons to kill adult mosquitoes may cause more harm than good.

There are more effective alternatives. Mosquito populations can be kept

under control using less toxic methods, such as less toxic bacterial

larvacides that can be applied to areas of standing water where mosquitoes

breed. Public education about careful avoidance of areas that are mosquito

havens, and basic common sense can help reduce the risk of disease. Once we

know where the disease originated, we can than take a more reasonable

approach to this public health threat.

In the meantime, NYC residents should be warned of the dangers of malathion

and should be strongly encouraged to avoid exposure, by staying indoors and

avoiding contact with sprayed areas. Malathion has a half life in soil of

1-25 days, in water between 1-6 weeks and in the air for 1.5 days. Most at

risk are children, the elderly, pregnant women, those with neurological

disorders, immune disorders and pre-existing diseases.

NYCAP maintains an information clearinghouse on pesticide hazards and

alternatives. We can be reached at 518-426-8246.

Pam Hadad Hurst

Executive Director

E X T O X N E T

Extension Toxicology Network

Pesticide Information Profiles

A Pesticide Information Project of ative Extension Offices of Cornell

University, Oregon State University, the University of Idaho, and the

University of California at and the Institute for Environmental

Toxicology, Michigan State University. Major support and funding was

provided by the USDA/Extension Service/National Agricultural Pesticide

Impact Assessment Program.

EXTOXNET primary files maintained and archived at Oregon State University

Revised June 1996

Malathion

Trade and Other Names: Malathion is also known as carbophos, maldison and

mercaptothion. Trade names for products containing malathion include

Celthion, Cythion, Dielathion, El 4049, Emmaton, Exathios, Fyfanon and

Hilthion, Karbofos and Maltox.

Regulatory Status: Malathion is a slightly toxic compound in EPA toxicity

class III. Labels for products containing it must carry the Signal Word

CAUTION. Malathion is a General Use Pesticide (GUP). It is available in

emulsifiable concentrate, wettable powder, dustable powder, and ultra low

volume liquid formulations.

Chemical Class: organophosphate

Introduction: Malathion is a nonsystemic, wide-spectrum organophosphate

insecticide. It was one of the earliest organophosphate insecticides

developed (introduced in 1950). Malathion is suited for the control of

sucking and chewing insects on fruits and vegetables, and is also used to

control mosquitoes, flies, household insects, animal parasites

(ectoparasites), and head and body lice. Malathion may also be found in

formulations with many other pesticides.

Formulation: It is available in emulsifiable concentrate, wettable powder,

dustable powder, and ULV liquid formulations. Malathion may also be found

in formulations with many other pesticides.

Toxicological Effects:

Acute toxicity: Malathion is slightly toxic via the oral route, with

reported oral LD50 values of 1000 mg/kg to greater than 10,000 mg/kg in the

rat, and 400 mg/kg to greater than 4000 mg/kg in the mouse [2,13]. It is

also slightly toxic via the dermal route, with reported dermal LD50 values

of greater than 4000 mg/kg in rats [2,13]. Effects of malathion are similar

to those observed with other organophosphates, except that larger doses are

required to produce them [2,8]. It has been reported that single doses of

malathion may affect immune system response [2]. Symptoms of acute exposure

to organophosphate or cholinesterase-inhibiting compounds may include the

following: numbness, tingling sensations, incoordination, headache,

dizziness, tremor, nausea, abdominal cramps, sweating, blurred vision,

difficulty breathing or respiratory depression, and slow heartbeat. Very

high doses may result in unconsciousness, incontinence, and convulsions or

fatality. The acute effects of malathion depend on product purity and the

route of exposure [33]. Other factors which may influence the observed

toxicity of malathion include the amount of protein in the diet and gender.

As protein intake decreased, malathion was increasingly toxic to the rats

[78]. Malathion has been shown to have different toxicities in male and

female rats and humans due to metabolism, storage, and excretion

differences between the sexes, with females being much more susceptible

than males [79]. Numerous malathion poisoning incidents have occurred among

pesticide workers and small children through accidental exposure. In one

reported case of malathion poisoning, an infant exhibited severe signs of

cholinesterase inhibition after exposure to an aerosol bomb containing 0.5%

malathion [44].

Chronic toxicity: Human volunteers fed very low doses of malathion for 1

1/2 months showed no significant effects on blood cholinesterase activity.

Rats fed dietary doses of 5 mg/kg/day to 25 mg/kg/day over 2 years showed

no symptoms apart from depressed cholinesterase activity. When small

amounts of the compound were administered for 8 weeks, rats showed no

adverse effects on whole-blood cholinesterase activity [2]. Weanling male

rats were twice as susceptible to malathion as adults.

Reproductive effects: Several studies have documented developmental and

reproductive effects due to high doses of malathion in test animals [2].

Rats fed high doses of 240 mg/kg/day during pregnancy showed an increased

rate of newborn mortality. However, malathion fed to rats at low dosages

caused no reproductive effects [8]. It is not likely that malathion will

cause reproductive effects in humans under normal circumstances.

Teratogenic effects: Rats fed high doses (240 mg/kg/day) showed no

teratogenic effects. Malathion and its metabolites can cross the placenta

of the goat and depress cholinesterase activity of the fetus [8]. Chickens

fed diets at low doses for 2 years showed no adverse effects on egg

hatching [8]. Current evidence indicates that malathion is not teratogenic.

Mutagenic effects: Malathion produced detectable mutations in three

different types of cultured human cells, including white blood cells and

lymph cells [2,8]. It is not clear what the implications of these results

are for humans.

Carcinogenic effects: Female rats on dietary doses of approximately 500

mg/kg/day of malathion for 2 years did not develop tumors [2]. Adrenal

tumors developed in the males at low doses, but not at the high doses [80],

suggesting that malathion was not the cause. Three of five studies that

have investigated the carcinogenicity of malathion have found that the

compound does not produce tumors in the test animals. The two other studies

have been determined to be unacceptible studies and the results discounted

[2,8,80]. Available evidence suggests that malathion is not carcinogenic

but the data are not conclusive.

Organ toxicity: The pesticide has been shown in animal testing and from use

experience to affect the central nervous system, immune system, adrenal

glands, liver, and blood.

Fate in humans and animals: Malathion is rapidly and effectively absorbed

by practically all routes including the gastrointestinal tract, skin,

mucous membranes, and lungs. Malathion undergoes similar detoxification

mechanisms to other organophosphates, but it can also be rendered nontoxic

via another simple mechanism, splitting of either of the carboxy ester

linkages. Animal studies indicate it is very rapidly eliminated though

urine, feces and expired air with a reported half-life of approximately 8

hours in rats and approximately 2 days in cows [2]. Autopsy samples from

one individual who had ingested large amounts of malathion showed a

substantial portion in the stomach and intestines, a small amount in fat

tissue, and no detectable levels in the liver. Malathion requires

conversion to malaoxon to become an active anticholinesterase agent. Most

of the occupational evidence indicates a low chronic toxicity for

malathion. One important exception to this was traced to impurities in the

formulation of the pesticide [2].

Ecological Effects:

Effects on birds: Malathion is moderately toxic to birds. The reported

acute oral LD50 values are: in mallards, 1485 mg/kg; in pheasants, 167

mg/kg; in blackbirds and starlings, over 100 mg/kg; and in chickens, 525

mg/kg [2,6]. The reported 5- to 8-day dietary LC50 is over 3000 ppm in

Japanese quail, mallard, and northern bobwhite, and is 2639 ppm in

ring-neck pheasants [6]. Furthermore, 90% of the dose to birds was

metabolized and excreted in 24 hours via urine [79].

Effects on aquatic organisms: Malathion has a wide range of toxicities in

fish, extending from very highly toxic in the walleye (96-hour LC50 of 0.06

mg/L) to highly toxic in brown trout (0.1 mg/L) and the cutthroat trout

(0.28 mg/L), moderately toxic in fathead minnows (8.6 mg/L) and slightly

toxic in goldfish (10.7 mg/L) [13,8,16]. Various aquatic invertebrates are

extremely sensitive, with EC50 values from 1 ug/L to 1 mg/L [28]. Malathion

is highly toxic to aquatic invertebrates and to the aquatic stages of

amphibians. Because of its very short half-life, malathion is not expected

to bioconcentrate in aquatic organisms. However, brown shrimp showed an

average concentration of 869 and 959 times the ambient water concentration

in two separate samples [12].

Effects on other organisms: The compound is highly toxic to honeybees [13].

Environmental Fate:

Breakdown in soil and groundwater: Malathion is of low persistence in soil

with reported field half-lives of 1 to 25 days [19]. Degradation in soil is

rapid and related to the degree of soil binding [12]. Breakdown occurs by a

combination of biological degradation and nonbiological reaction with water

[12]. If released to the atmosphere, malathion will break down rapidly in

sunlight, with a reported half-life in air of about 1.5 days [12]. It is

moderately bound to soils, and is soluble in water, so it may pose a risk

of groundwater or surface water contamination in situations which may be

less conducive to breakdown. The compound was detected in 12 of 3252

different groundwater sources in two different states, and in small

concentrations in several wells in California, with a highest concentration

of 6.17 ug/L [33].

Breakdown in water: In raw river water, the half-life is less than 1 week,

whereas malathion remained stable in distilled water for 3 weeks [12].

Applied at 1 to 6 lb/acre in log ponds for mosquito control, it was

effective for 2.5 to 6 weeks [12]. In sterile seawater, the degradation

increases with increased salinity. The breakdown products in water are

mono- and dicarboxylic acids [12].

Breakdown in vegetation: Residues were found mainly associated with areas

of high lipid content in the plant. Increased moisture content increased

degradation [33].

Physical Properties:

Appearance: Technical malathion is a clear, amber liquid at room

temperature [13].

Chemical Name: diethyl (dimethoxy thiophosphorylthio) succinate [13]

CAS Number: 121-75-5

Molecular Weight: 330.36

Water Solubility: 130 mg/L [13]

Solubility in Other Solvents: v.s. in most organic solvents [13]

Melting Point: 2.85 C [13]

Vapor Pressure: 5.3 mPa @ 30 C [13]

Partition Coefficient: 2.7482 [13]

Adsorption Coefficient: 1800 [19]

Exposure Guidelines:

ADI: 0.02 mg/kg/day [38]

MCL: Not Available

RfD: 0.02 mg/kg/day [53]

PEL: 15 mg/m3 (8-hour) (dust) [39]

HA: 0.2 mg/L (lifetime) [53]

TLV: Not Available

Basic Manufacturer:

Drexel Chemical Company 1700 Channel Avenue

Memphis, TN 38113

Phone: 901-774-4370

Emergency: Not Available

References:

References for the information in this PIP can be found in Reference List

<reflist5.htm>Number 5