The effect of pesticide spraying on the rate and severity of ED asthma

The effect of pesticide spraying on the rate and severity of ED asthma

Bonnie Chin-Yet O’Sullivan MDa, John Lafleur MDa, Kirsa Fridal MDa,

Stephen Hormozdi MDa, Steve Schwartz MDb, Mark Belt MDa, Madelon Finkel PhDc,*

aDepartment of Emergency Medicine, Lincoln Medical and Mental Health Center, Bronx, NY 10451, USA bDepartment of Emergency Medicine, North Shore Medical Center, Long Island, NY 11030, USA cDepartment of Public Health, Weill Medical College, Cornell University, New York, NY 10021, USA

Received 26 August 2004; accepted 7 December 2004

Abstract We report on the incidence of emergency department (ED) asthma presentations and admissions to the Lincoln Hospital, located in the South Bronx of New York City, during the 1999 eradication program of the mosquito vector for West Nile virus. Spraying of Malathion and Resmethrin occurred in the hospital’s geographic area over 4 days in September 1999. During that time, 1318 pediatric and adult patients were seen in the ED for asthma-related symptoms. Of these, 222 (16.8%) were hospitalized. Emergency department visits, during days when spraying occurred, were compared with visits during days when no spraying occurred. Comparisons were made with previous years as a reference point. Findings showed that the spraying of insecticides did not increase the rate or severity of asthma presentations as measured by the Lincoln Hospital’s ED asthma census or hospital admissions for asthma.

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The first known outbreak of the West Nile virus in the western hemisphere occurred in the summer of 1999 in an area in northern Queens, a borough of New York City. The New York City Department of Health (DOH) received a report of an unusual cluster of cases of meningoenceph- alitis associated with muscle weakness suggestive of an arboviral cause. An environmental investigation was undertaken and, simultaneously, an independent investiga-

* Corresponding author. Tel.: +1 212 746 1257; fax: +1 212 746 8544.

E-mail address: [email protected] (M. Finkel).

tion by veterinarians and wildlife specialists found pathological evidence of a Flavivirus later identified as West Nile virus [1,2].

The DOH, after careful consideration of the risks of spraying to the general public, responded by initiating a citywide spraying campaign in an effort to control the outbreak. This decision was based on its assessment that the potential for risks to the general population was low. The spraying during the fall of 1999 occurred under emergency conditions and thus was considered exempt from the State and City Environmental Quality Review Acts. Ultralow volume (0.6-3.0 oz/acre quantities) Malathion was sprayed from helicopters and Resmethrin was sprayed from trucks (0.11-0.34 oz/acre) [3].

0735-6757/$ – see front matter D 2005 doi:10.1016/j.ajem.2004.12.017

Insecticide toxicity

Eradication of mosquito vectors may be accomplished by spraying of insecticides, although these have known toxicity to human beings depending on the dosage and extent of exposure [4,5]. Malathion is an organophosphate insecticide that can be absorbed through virtually any route [6]. Organophosphates exert their toxicity primarily by the inhibition of acetylcholinesterase, resulting in excess accu- mulation of acetylcholine at the synapse. Organophosphate toxicity compromises the airway via a muscarinic effect, causing bronchorrhea and bronchospasm. Onset of symp- toms is most rapid after inhalation and least rapid after percutaneous absorption. Most patients become symptom- atic within 12 hours of exposure. Routine occupational exposure to Malathion regularly causes wheezing even in patients without asthma [7,8].

Resmethrin is a man-made pyrethroid insecticide found to be effective against adult mosquitoes including Culex, the species most commonly associated with the West Nile virus. Pyrethroids, synthetic analogs of natural pyrethrins, are active extracts from Chrysanthemum cinerariaefolium [9]. The major site of action of all pyrethroids has been shown to be a voltage-dependent sodium channel. Poisoning syn- dromes manifest as reflex hyperexcitability, fine tremor, salivation, choreoathtosis, and seizures [10]. In general, pyrethroids are much less acutely toxic to rats and presum- ably to human beings than are the natural pyrethrins. Although the mechanism of toxicity of pyrethroids is not known to induce bronchospasm, wheezing in response to tetramethrin (a pyrethroid) has been reported [11]. In addition, there is a well-documented bronchospastic reaction that occurs with acute exposures to pyrethrins in sensitized patients, as well as several case reports of fatality from bronchospasm associated with a pyrethrin shampoo [12,13]. The effect of spraying of insecticides on the health of the exposed population was of concern to the DOH. In particular, the risks of exacerbating airway disease among vulnerable populations, notably among asthmatics, needed to be taken into account. Only one study in the literature examined the risk posed to asthmatics by insecticide spraying over urban areas and findings showed neither an increase in shortness of breath after spraying of Malathion in Santa Clara County, California, nor increased emergency

department (ED) use for asthma-like symptoms [14].

Rationale for study

This study seeks to ascertain adverse risks of insecticide spraying in an area that has one of the highest rates of asthma in New York City. This study seeks to answer the question bTo what extent did the spraying of insecticides over the South Bronx in 1999 contribute to an increase in asthmatic symptoms as measured by ED presentations?Q It was hypothesized that the spraying of insecticides was not

likely to have adverse health consequences to those exposed. Indeed it was thought that there would be less significant risks from spraying than there would be risks by transmission of the West Nile virus from mosquito bites [15]. It was assumed that any adverse effect of pesticide spraying would be evident by an increase in visits for asthma to the Lincoln Hospital’s adult and pediatric EDs.

Study area

The densely populated South Bronx area of New York City has one of the highest rates of hospitalization and death from asthma [16-18] Hospitalization for asthma among those younger than 14 years in this area was approximately 23 per 1000 in 1997. The New York State, by contrast, had about one tenth the hospital admissions for asthma in this age group (2.4 per 1000) [19]. The ED at the Lincoln Hospital sees approximately 14 500 asthma visits per year, resulting in 1500 annual hospital admissions for this disease and representing about 5% of all asthma hospitalizations in New York City [20]. The ED sees a full spectrum of asthmatic symptoms, not just the most acute presentations, because most asthmatic patients tend to use the ED for both primary and emergency care.

During the mosquito eradication program in 1999 in this area, 5349 gallons of Adulticide were used in the West Nile eradication effort, and Malathion made up 4561 gallons, or about 80%, of that [21]. Malathion was sprayed from helicopters and Resmethrin from trucks. The South Bronx, which contains a large majority of the Lincoln Hospital’s patient population, was sprayed on 4 days in September 1999: on the 11th, 12th, 13th, and again on the 20th. Spraying occurred during evening hours and continued past midnight into the early hours of the following morning.


A retrospective review of all pediatric and adult asthma visits and asthma hospital admissions for August and September of 1999 was undertaken. Included were all patients with a primary diagnosis of asthma from the ED. To assess the usual patterns of asthma presentations to the ED, data were also collected on all adult and Pediatric asthma ED visits for August and September of 1997 and 1998. Asthma presentations to and admission rates from the adult and pediatric EDs were noted for the 11th, 12th, 13th, and 20th of September, the days the city conducted spraying in the South Bronx. These data were compared with the other days of the month when no spraying occurred. To account for the fact that spraying was conducted before and after midnight on the spraying days, we conducted the same analysis for the 12th, 13th, 14th, and 21st of September as well. A third analysis compared the 5 days after each spraying episode with the days of nonspraying to capture any delayed

Fig. 1 Emergency department asthma visits (adult and pediatric).

presentation to the ED. Two-tailed Student t tests with a set at

.05 were used to calculate statistical significance.


Fig. 1 shows asthma presentations to the adult and pediatric EDs for August and September of 1997, 1998, and 1999. The expected seasonal increase in asthma was consistent for each year. During September 1999, a total

of 1318 patients presented to the Lincoln Hospital ED with a primary diagnosis of asthma exacerbation (753 or 57.1% adult patients and 565 or 42.9% pediatric patients). Of those patients, 222 (16.8%) were admitted (102 or 45.9% adult patients and 120 or 54.1% pediatric patients). When rates of admission for asthma in September 1999 were compared with those in September 1997 and September 1998, no significant differences were seen. Twenty-four percent of pediatric patients seen in the ED for asthma were admitted in 1997 vs 22% in 1998 and 27% in 1999. Among adult

Fig. 2 Comparison of daily visits and admission for spraying vs nonspraying days.

Fig. 3 Adult asthma visits (3-day running average).

patients seen in the ED for asthma, approximately 16% were admitted to the hospital during all 3 periods.

The data show that in 1999, the adult ED evaluated approximately 25.1 patients with asthma per day on the nonspraying days and 25 patients per day on the spraying days. In the pediatric ED, 19.3 asthma patients were evaluated per day on the nonspraying days and 15.8 patients on the spraying days. These differences are not statistically significant.

Data collected on the 12th, 13th, 14th, and 21st of September show that an average of 22 asthma patients per day was evaluated in the adult ED whereas 13 patients per day were evaluated in the pediatric ED. Fig. 2 illustrates the average number of ED asthma visits and hospital admissions per day for the adult and pediatric EDs in September 1999. The admission rate was used as an indicator for the severity of illness. The percentage of total adults with asthma who were admitted to the hospital during September 1999 was 13.6%

on the nonspraying days and 13.0% on the spraying days. The percentage of pediatric admissions on nonspraying and spraying days was 20.7% and 25.4%, respectively.

A 5-day running average of patient ED asthma visits was calculated to account for possible delayed effects of spraying; no significant difference between spraying and nonspraying days was seen. Figs. 3 and 4 show adult and pediatric ED visits during September 1999. There were no statistically significant differences between spraying and nonspraying days in September 1999.


Since the first outbreak of the West Nile virus in New York City in 1999, the virus has spread across most of the United States and has become enzootic and endemic in the central and eastern parts of the country and

Fig. 4 Pediatric asthma visits (3-day running average).

increasingly in the West; there have been more than 200 known deaths in the United States from this arbovirus, primarily among the elderly individuals [22]. Transmis- sion of the West Nile virus has been found to occur through Organ donation, blood transfusions, and breast feeding [23]; intrauterine transmission also has been recently reported [24].

Certainly, the rapid spread of this dangerous disease is a cause for concern, and Public health measures, including eradication of its mosquito vector, seem warranted. Yet, in light of the very high burden of asthma morbidity and mortality in the South Bronx, the spraying of insecticides in this Inner city, an urban population with a high prevalence of asthma, was a cause for concern given the potential for exacerbation of the disease. Findings from this study showed no acute effect on asthma patients after insecticide spraying. The New York City DOH reported on citywide statistics for hospital-based Treatment of asthma during the mosquito eradication of September 1999 and found no significant increases in hospital admissions or acute outpatient asthma care during the period of interest [25].

Although this study showed no increase in asthma-like symptoms as a result of spraying, we acknowledge limitations that may have influenced the results. Our methodology does not allow us to assess individual exposures to insecticides. Also, because of the small number of spraying days and a changing baseline caused by seasonal variability, subtle acute effects of spraying on asthmatic airways could have been missed. Possible confounders include other factors relating to air quality such as ozone and particulate matter and epidemics of viral upper airway infections. Finally, the epidemiology of asthma is complicated, multifactorial, and incompletely understood. The Long-term effects on individuals with asthma or on those at risk for developing asthma of exposure to chemicals such as Malathion and Resmethrin are difficult if not impossible to predict.

Given the high concentration of asthma patients in the Lincoln Hospital population and the high volume of asthma patients treated at the ED, it is unlikely that a significant number of patients in the South Bronx would develop clinically significant symptoms of bronchospasm without there being a corresponding increase in emergency asthma presentations to the Lincoln Hospital. We feel confident that the sample of patients presenting to the Lincoln Hospital with asthma during the study period is representative of the experience of individuals with asthma in the South Bronx during September 1999. Therefore, we are confident that the data presented accurately portray the negligible effect of insecticide spraying on this study population as reflected by those seeking care for asthma during the spraying.


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