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Subject: [WNV-L] CDC Surveillance Summary of Acute Illness from Mosquito Controls
Date:
July 11, 2003
Posted by:
Lois Levitan (lcl3@cornell.edu)
[1] Comment re: Pesticide Effects, Hazards and Exposure
[2] CDC MMWR Surveillance Summary for Acute Insecticide-Related Illness Associated with Mosquito-Control
[1]
The Editorial Note to this study of acute pesticide poisonings
associated with mosquito control insecticides concludes that
"serious adverse outcomes potentially related to public health
insecticide application [a]re uncommon. When administered properly in
a mosquito-control program, insecticides pose a low risk for acute,
temporary health effects."
The authors and/or editor also make several other important points.
(a) They note that CDC recommends integrated pest management
(IPM) strategies for mosquito-control programs as the best means to
reduce potential risks from insecticide exposure. IPM emphasizes
mosquito larval control and reduction of breeding sites. The
Editorial Note also points out that CDC advises public health
agencies to inform the public when and where spraying will occur,
communicate how to reduce the likelihood of exposure, and train
insecticide handlers and applicators in proper insecticide handling
and application methods.
(b) Accidents happen: Without (or perhaps despite) such
training, accidents do happen. In fact, the article notes that more
than half of the 49 pesticide poisoning cases identified in 2001
occurred when workers operating a mosquito-control truck
inadvertently sprayed people at a softball game, all of whom required
treatment in emergency departments. My own editorial comment is that
we cannot expect that pesticides will always be administered
properly. Therefore we should not base policies regarding use of
hazardous materials on the assumption that they will always be
handled per letter of the law.
(c) The Editorial Note points out several reasons why case
numbers may be under-reported (or over-reported) and implies that the
numbers of persons poisoned by mosquito control pesticides cannot be
directly compared with the numbers of people who contracted WNV
because the case numbers are only from the 9 states that maintain
pesticide poisoning surveillance systems (the other 41 states do not
do such surveillance).
I would like to make the additional point that these
surveillance systems are designed to record only acute (immediate)
effects of pesticide exposure. Neither these surveillance registries
nor the EPA acute toxicity categories (mentioned in a footnote at the
end of the article) reflect more subtle, interactive or delayed
effects of pesticides on human health or the environment. In other
words, the pesticide poisoning surveillance systems are an important
means for keeping a "finger on the pulse," but they are just one of
many needed means for assessing unintended consequences of pesticide
use.
In sum, I was very pleased to see the study results and thoughtful
commentary in the MMWR -- Lois Levitan
-------
[2]
SURVEILLANCE FOR ACUTE INSECTICIDE-RELATED ILLNESS ASSOCIATED WITH
MOSQUITO-CONTROL EFFORTS -- Nine States, 1999-2002.
July 11, 2003 edition of CDC's Morbidity and Mortality Weekly Report
(Vol.52/No.27) (full text, including Tables:
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5227a1.htm)
EXCERPTS:
...This report summarizes investigations of illnesses associated with
exposures to insecticides used during 1999--2002 to control mosquito
populations in nine states (Arizona, California, Florida, Louisiana,
Michigan, New York, Oregon, Texas, and Washington) (estimated 2000
population: 118 million).
The findings indicate that application of certain insecticides posed
a low risk for acute, temporary health effects among persons in areas
that were sprayed and among workers handling and applying
insecticides.
To reduce the risk for negative health effects, public health
authorities should
1) provide public notice of application times and locations and
appropriate advice about preventing exposures,
2) ensure that insecticide handlers and applicators meet
state-mandated training and experience requirements to prevent
insecticide exposure to themselves and the public, and
3) implement integrated pest management control strategies that
emphasize mosquito larval control, reduction of mosquito breeding
sites, and judicious use of insecticides to control adult mosquito
populations.
Staff in state-based pesticide poisoning surveillance programs
identified patients who had been exposed to insecticides used in
mosquito-control efforts in nine states during April 1999--September
2002. Information was gathered on persons who had illnesses
consistent with the national case definition for pesticide poisoning,
which requires the collection of data on pesticide exposure, health
effects, and toxicologic evidence supporting an association between
exposure and effect (2,3). Cases of insecticide-related illness or
injury were classified as either definite, probable, or possible,
depending on the certainty of exposure and whether health effects
were signs observed by a health-care provider or symptoms reported by
a patient (2,3).
Of the 133 cases of acute insecticide-related illness associated with
mosquito control that were identified, two (1.5%) were classified as
definite, 25 (18.8%) as probable, and 106 (79.7%) as possible. Of the
132 cases for which work-relatedness could be assessed, 36 (27.3%)
were work-related and 96 (72.7%) were not work-related; 31 (86.1%) of
the 36 work-related cases occurred among males, and 66 (68.8%) of the
96 cases that were not work-related occurred among females.
Of the 49 cases identified in 2001, a total of 29 (59.2%) were
related to a single event at a softball game in which workers
operating a mosquito-control truck inadvertently sprayed 29 persons
(16 spectators, 12 players, and one coach) with Fyfanon ULVš, which
contains malathion. All 29 persons were treated in emergency
departments (EDs).
Of the 133 persons with acute insecticide-related illness associated
with mosquito control, 35 (26.3%) were identified from monitoring
media reports (including 34 reported subsequently by health-care
providers), 32 (24.1%) were reported by poison-control centers, 27
(20.3%) were self-reported, and seven (5.3%) were reported by state
health departments. Physicians and EDs were responsible for initial
reporting of five and three cases, respectively. The remaining cases
were reported initially by friends or relatives (n = seven),
government agencies (n = five), employers (n = four), laboratories (n
= two), and other sources (n = six).
Of the 85 persons with reported illness who were known to have sought
medical care, 45 (52.9%) were treated in EDs, 35 (41.2%) were treated
in physicians' offices, four (4.7%) were treated in employee health
centers, and one (1.2%) was hospitalized. An additional 16 persons
received advice from a poison-control center, and 15 did not seek
medical care; information about medical treatment was not available
for 17 persons.
Of the 133 reported cases of pesticide-related illness, 95 (71.4%)
cases were associated with organophosphates, primarily malathion.
Malathion alone was associated with 64 (67.4%) of the 95 cases; 37
(27.8%) cases were associated with pyrethoids, primarily sumithrin
(24 cases) and resmethrin (10 cases) (Table 1).
Illness severity was categorized for all cases (4). One exposure was
associated with illness of high severity (Table 2). When her
neighborhood was sprayed, a woman aged 54 years was exposed to
sumithrin, which passed through operating window fans and a window
air conditioner. She had exacerbation of her asthma and chronic
obstructive pulmonary disease. The majority of the remaining cases
were of low (65.4%) or moderate (33.8%) severity.
The majority of cases were associated either with respiratory (66.2%)
or neurologic (60.9%) dysfunction. Other systems affected were
gastrointestinal (45.1%), ocular (36.1%), dermal (27.1%),
cardiovascular (12.0%), renal-genitourinary (3.0%), and miscellaneous
(28.6%).
Of 36 persons who were exposed at their workplaces (Table 1), 14
(38.9%) were insecticide applicators, and 22 (61.1%) were performing
tasks that did not involve pesticide application. Seven (50.0%) of 14
applicators were exposed to sumithrin; of the other 22 workers, 11
(50%) were exposed to malathion, and five (22.7%) were exposed to
resmethrin. Illness of moderate severity was more frequent among
applicators (42.9%) than nonapplicators (27.3%).
Editorial Note:
The findings in this report indicate that serious adverse outcomes
potentially related to public health insecticide application were
uncommon. When administered properly in a mosquito-control program,
insecticides pose a low risk for acute, temporary health effects
among persons in areas that are being sprayed and among workers
handling and applying insecticides. In this analysis, adverse health
effects were identified in a small percentage of the population in
the nine states. Data about the actual number of persons potentially
or actually exposed were not available because insecticide
applications were conducted only in certain areas of participating
states, and the boundaries of these areas were not available.
Malathion, naled, sumithrin, and resmethrin were associated with the
majority of reported cases of acute insecticide-related illness.
Malathion is an organophosphate insecticide that is classified as an
acute toxicity category III compound*. Although it is less acutely
toxic than many other organophosphates, adverse health effects have
been reported by exposed persons (5). Naled is an acute toxicity
level I organophosphate. When combined with piperonyl butoxide,
resmethrin and sumithrin are highly effective insecticides that are
of low-order toxicity to mammals, including humans; these pyrethroid
products are classified as acute toxicity category III compounds and
have been associated with adverse health effects in humans (6,7).
These insecticide formulations are registered by the U.S.
Environmental Protection Agency for use in urban areas for mosquito
control and benefit the public by controlling populations of
mosquitoes that transmit diseases that affect humans. Reported
symptoms associated with these insecticides were temporary and
included dermal, ocular, and upper and lower respiratory tract
irritation and exacerbation of conditions such as asthma. These
health effects might represent irritant or allergic responses, to
either the insecticide or its carrier (5,7,8). Anxiety about
insecticide use for mosquito control also might have been responsible
for symptoms in some persons.
The findings in this report are subject to at least three limitations.
1) The number of reported cases is probably an underestimate of the
true magnitude of illnesses associated with
mosquito-control efforts. Affected persons who did not seek medical
care or whose symptoms were not reported to a surveillance system
could not be identified; even if these persons had sought medical
care, their illness might not have been recognized as
insecticide-related, and even if they had received a proper
diagnosis, their cases might not have been reported.
2) Only nine states have pesticide poisoning surveillance systems,
and the data in this report might not be representative of the 41
states without such surveillance systems.
3) Although all cases were consistent with case definition criteria,
the possibility of false positives cannot be excluded. Because
clinical findings of pesticide poisoning are nonspecific, especially
when of mild severity, and no
standard diagnostic test exists, some illnesses related temporally to
insecticide exposures might be coincidental and not caused by the
exposures.
To reduce potential risks from insecticide exposure, CDC recommends
the use of integrated pest management strategies for mosquito-control
programs that emphasize mosquito larval control, reduction of
breeding sites (e.g., human-made collections of stagnant water such
as unchlorinated swimming pools, discarded tires or other containers,
and bird baths), and judicious use of insecticides to control adult
mosquito populations when quantitative measures suggest an elevated
risk for human infection or in community settings when extensive
immature mosquito larval habitats cannot be controlled (9,10). When
insecticides are used, public health agencies should inform the
public when and where spraying will occur and communicate how to
reduce the likelihood of exposure. To avoid direct exposure from
passing spray trucks, public health agencies should ensure that
visible and audible warnings are made before spraying. Persons with
exposure-related health concerns should consult their health-care
providers. To prevent exposures from improper application methods,
insecticide handlers and applicators should be trained in proper
insecticide handling and application methods and in the use of
appropriate personal protective equipment.
References
1. U.S. Environmental Protection Agency and CDC. Joint statement
on mosquito control in the United States from the U.S. Environmental
Protection Agency (EPA) and the U.S. Centers for Disease Control and
Prevention (CDC). Available at
http://www.epa.gov/pesticides/factsheets/mosquitojoint.htm.
2. CDC. Case definition for acute pesticide-related illness and
injury cases reportable to the National Public Health Surveillance
System. Available at
http://www.cdc.gov/niosh/pestsurv/pdfs/pest-casdef2000.pdf.
3. Calvert GM, Sanderson WT, Barnett M, Blondell JM, Mehler LN.
Surveillance of pesticide-related illnesses and injury in humans. In:
Krieger R, ed. Handbook of Pesticide Toxicology, 2nd ed. San Diego,
California: Academic Press, 2001.
4. CDC. Severity index for use in state-based surveillance of
acute pesticide-related illness and injury. Available at
http://www.cdc.gov/niosh/pestsurv/pdfs/pest-sevindexv6.pdf.
5. CDC. Surveillance for acute pesticide-related illness during
the medfly eradication program---Florida, 1998. MMWR 1999;48:1015--8.
6. Gibly RL, Sullivan JB. Pyrethrins. In: Sullivan JB, Krieger GR,
eds. Clinical Environmental Health and Toxic Exposures, 2nd ed.
Philadelphia, Pennsylvania: Lippincott Williams & Wilkins, 2001.
7. Reigart JR, Roberts JR, eds. Pyrethroids. In: Recognition and
Management of Pesticide Poisonings, 5th ed. Washington, DC: U.S.
Environmental Protection Agency, 1999. Available at
http://www.epa.gov/pesticides/safety/healthcare/handbook/handbook.htm.
8. Wagner SL. Allergy from pyrethrin or pyrethroid insecticides. J
Agromed 1994;1:39--45.
9. Nasci RS, Newton NH, Terrillion GF, et al. Interventions:
vector control and public education: panel discussion. Ann N Y Acad
Sci 2001;951:235--54.
10. Thier A. Balancing the risks: vector control and pesticide use
in response to emerging illness. J Urban Health 2001;78:372--81.
* The U.S. Environmental Protection Agency classifies pesticide
products into one of four acute toxicity categories on the basis of
certain criteria, with category I comprising pesticides with the
greatest toxicity and category IV those with the least toxicity.
--
Lois Levitan, PhD Program Leader
Environmental Risk Analysis Program
Department of Communication and
Center for the Environment
213 Rice Hall, Cornell University
Ithaca, New York USA 14853-5601
Phone: (607) 255-4765 Fax: (607) 255-0238
Email: LCL3@cornell.edu
Web: http://environmentalrisk.cornell.edu