Pesticide illness among flight attendants due to aircraft disinsection

AMERICAN JOURNAL OF INDUSTRIAL MEDICINE 50:345–356 (2007) Pesticide Illness Among Flight Attendants Patrice M. Sutton, MPH,1{ Ximena Vergara, MPH,1{ John Beckman, BS,1{ Background Aircraft ‘‘disinsection’’ is the application of pesticides inside an aircraft tokill insects that may be on board. Over a 1-year period, California’s tracking systemreceived 17 reports of illness involving flight attendants exposed to pesticides followingdisinsection.
Methods Interviews, work process observations, and a records review were conducted.
Illness reports were evaluated according to the case definition established by the NationalInstitute for Occupational Safety and Health.
Results Twelve cases met the definition for work-related pesticide illness. Eleven caseswere attributed to the ‘‘Residual’’ method of disinsection, i.e., application of a solution ofpermethrin (2.2% w/w), solvents (0.8%), and a surfactant (1.4%); the method ofdisinsection could not be determined for one case.
Conclusions The aerosol application of a pesticide in the confined space of an aircraftcabin poses a hazard to flight attendants. Nontoxic alternative methods, such as aircurtains, should be used to minimize disease vector importation via aircraft cabins.
Employers should mitigate flight attendant pesticide exposure in the interim. Am. J. Ind.
Med. 50:345–356, 2007. ß 2007 Wiley-Liss, Inc.
KEY WORDS: Occupational pesticide illness; flight attendants; aircraft disinsection;residual disinsection; permethrin; air curtains 1Public Health Institute, Oakland, California2 School of Public Health, University of California, Berkeley, California 3Occupational Health Branch, California Department of Health Services, Richmond, Aircraft disinsection is the application of pesticides Institution where the work was performed: California Department of Health, Services, inside an aircraft to kill insects that may be on board.
Occupational Health Branch, 850 Marina Bay Parkway, Building P, 3rd Floor, Richmond, CA94804 (510) 620-5757 Fax (510) 620-5743.
Disinsection is undertaken as a public health measure to address the potential threat posed by insects to the health of humans, plants, animals, and agriculture [Gratz et al., 2000; USDOT, 2006]. Airlines are required to perform this pro- Contract grant sponsor: This work was performed under a Cooperative Agreement, cedure to comply with quarantine regulations of some California Sentinel Event Notification System for Occupational Risks (SENSOR), between countries. Currently 21 countries require aircraft disinsection the California Department of Health Services Occupational Health Branch and the NationalInstitute for Occupational Safety and Health; Contract grant sponsor: Cooperative Agree- of all (N ¼ 16) or selected (N ¼ 5) inbound flights. Of the 16 ment; Contract grant number: U60/CCU902990.
countries that currently require disinsection, nine require the *Correspondence to: Rupali Das, Occupational Health Branch, California Department of pesticide to be applied while passengers are on board, and Health Services, 850 Marina Bay Parkway, Building P, 3rd Floor, Richmond, CA 94804 USA.
E-mail: rdas@dhs.ca.gov.
seven permit the use of an aerosolized spray while passengersare not on board. Most countries reserve the right to require disinsection should they perceive a threat to their public DOI 10.1002/ajim.20452. Published online in Wiley InterScience health, agriculture, or environment [USDOT, 2006].
In 1996, the U.S. Environmental Protection Agency after pre-flight spraying . . . [and] while they may cause (USEPA) determined that the benefit of disinsection in transient discomfort, pyrethroids do not indicate or predict occupied cabins may not exceed the risk, and that such use serious health effects’’ [WHO, 2005].
may result in unreasonable adverse effects on the environ- The California Department of Health Services (CDHS) ment [USEPA, 1996]. The U.S. government does not require Occupational Health Branch conducts statewide surveillance any disinsection procedure to be performed [USDOT, 2006], of acute work-related pesticide illness as part of the National and although the procedure is not explicitly prohibited, there Institute for Occupational Safety and Health (NIOSH) are no pesticides registered for use in the U.S. for aircraft Sentinel Event Notification System for Occupational Risk (SENSOR) Program. CDHS performs investigations of There are two approaches to disinsection used in the selected pesticide illness incidents to identify the causes of airline industry: the pesticide is applied by flight attendants in illness and to develop recommendations for primary the presence of passengers after the plane leaves the gate prevention of future illnesses. Between August 2000 and (Blocks-Away) and/or before it lands (Top-of-Descent), or August 2001, CDHS received physician reports of six the pesticide is applied by ground crew prior to passenger and incidents involving 17 flight attendants who reported flight crew boarding (Pre-Flight and Residual). Whereas the exposure to pesticides used during aircraft disinsection. All Blocks-Away, Top-of-Descent, and Pre-Flight applications incident reports involved flight attendants working on 747– are short-lived, the Residual application leaves a long-lasting 400 aircraft for a single employer. CDHS undertook an (56 days) pesticide residue in the aircraft cabin. Notification investigation to: (1) determine if the reported illnesses were for in-flight applications states that the spray is ‘‘nontoxic,’’ caused by pesticide exposure; (2) identify factors that may and there is no passenger notification for Residual applica- have contributed to documented illnesses; and (3) make recommendations to prevent pesticide poisoning.
Recommended procedures for aircraft disinsection are established by the World Health Organization (WHO) Expert Committee on Vector Biology and Control [WHO, 1985a,b,1995]. All methods of aircraft disinsection involve applying a synthetic pyrethroid, either permethrin or d-phenothrin,inside the aircraft cabin. Pyrethroids are synthetic derivatives The SENSOR program collected existing health and of natural pyrethrin compounds and are widely used as broad- hazard data pursuant to legislative authority of the CDHS spectrum insecticides [Ray and Forshaw, 2000; Bradberry (California Health and Safety Code 105175; 100325; and et al., 2005]. Both pyrethrins and pyrethroids exert their toxic 100330). SENSOR protocols have been approved by the effects by prolonging the inactivation of sodium channels California Health and Human Services Agency Committee in the peripheral and central nervous systems [Coats, 1990; for the Protection of Human Subjects.
Ray, 1991; He, 1994; Bradberry et al., 2005]. Exposure to To investigate the reports of illness among flight synthetic pyrethroids can cause abnormal sensations on attendants following aircraft disinsection, SENSOR project exposed skin, contact dermatitis, dizziness, nausea, anorexia, staff attempted to interview all 17 flight attendants with a fatigue, mild disturbances of consciousness, muscular reported illness. Flight attendants were phoned at least three fasciculations, and, at high doses, pulmonary edema, times at their homes and once contacted they were asked to convulsions, and coma [He et al., 1989; Bradberry et al., participate in a voluntary telephone interview. On initial 2005; Spencer and O’Malley, 2006]. Pyrethroid pesticides contact with workers, project staff read them an informed are highly toxic to insects as well as to aquatic life [Weston consent script and sought their verbal consent to participate.
et al., 2005]. Acute toxicity in mammals is limited because Workers who agreed to participate were surveyed using a pyrethroids are rapidly detoxified in the blood and liver to structured questionnaire in which workers were queried their inactive components [Ray and Forshaw, 2000].
about their incident-specific work duties, exposures, signs The signs and symptoms of exposure to permethrin and symptoms, and medical follow-up. In addition project include irritation of the eyes and upper respiratory tract; staff: (1) requested medical records from the treating irritation, burning, and itching of the skin; and urticaria physician(s) for all 17 flight attendants; (2) conducted an [Kolmodin-Hedman et al., 1982; Fuortes, 1999]. Aerosolized on-site investigation at the employer’s aircraft maintenance pyrethroid insecticides used for disinsection may trigger non- center, including a walk-through of a 747–400 aircraft; specific bronchoconstriction and respiratory symptoms in (3) interviewed employer and employee representatives using asthmatics [WHO, 1995]. In its most recent evaluation of the a detailed industrial hygiene checklist about the aircraft safety of pyrethroids used for aircraft disinsection, WHO disinsection work process, tasks, and exposure control concluded ‘‘paraesthesias and, in inhalation exposure, upper measures; (4) viewed a video that documented the Residual respiratory tract irritation, . . . may occur among aircraft disinsection of a 747–400 aircraft; and (5) reviewed the passengers and crew after in-flight spraying and among crew employer’s written records about aircraft disinsection, Pesticide Illness Due to Aircraft Disinsection including: the pesticide products used, application policy and procedures, safety and health programs, results of industrialhygiene monitoring conducted by the employer, aircraft A total of 12 of 17 flight attendants met the NIOSH ventilation rates, logs of visits to the employer’s medical definition for work-related pesticide illness based on: (1) timely, facilities in San Francisco and Los Angeles, and additional self-reported evidence of exposure made to a licensed health care professional; (2) the presence of two or more new post-exposure abnormal health effects (symptoms reported by aworker, signs reported by a licensed health care provider) and/or test or laboratory findings; and (3) health effects thatare consistent with the known toxicology of the pesticide All illness reports were evaluated according to: applied to the aircraft [NIOSH, 2005]. For five illness reports, (1) NIOSH guidelines for evaluation of pesticide illness there was insufficient information available to confirm or rule [NIOSH, 2005]; (2) the presence of one or more routes of out that the flight attendants’ illnesses were pesticide-related.
pesticide exposure; and (3) the presence, use, and efficacy of The sources of data, medical information, and exposure measures to limit flight attendant pesticide exposure. NIOSH characteristics of the 12 cases are presented in Table I. The defines a case as acute onset of symptoms that are consistent 12 cases involved three separate incidents that occurred with the pesticide formulation, and that involve systemic between August 2000 and March 2001. Two incidents signs or symptoms, dermatologic lesions, and/or ocular involved 1 flight attendant each, and the third involved lesions. A report was classified as work-related pesticide 10 flight attendants. Two incidents (11 cases) involved a illness if all of the following criteria were met: (1) exposure Residual application of permethrin. In the third incident, the occurred while working; (2) the exposure was documented; method of disinsection could not be determined by CDHS.
(3) two or more adverse health effects were documented; All 12 cases of pesticide illness involved exposure to a and (4) there was evidence in the scientific literature that pesticide that was applied on aircraft in Australia (Sydney) supported a causal relationship between pesticide exposure prior to traveling to the U.S. (Los Angeles).
Of the 12 cases, eight flight attendants experienced symptoms immediately or shortly after boarding the aircraftand two within an hour of boarding. Specific information on the timing of onset of symptoms was missing for two flightattendants. The most common signs and symptoms experi- An occupational health physician and industrial hygie- enced were respiratory (N ¼ 12), nervous system (N ¼ 11), nist reviewed available medical, worker interview, and dermatological (N ¼ 9), eye (N ¼ 9), cardiovascular (N ¼ 5), employer records for all illness reports. Descriptive statistics and gastrointestinal (N ¼ 6) (Table II).
were used to analyze the illness and industrial hygiene data.
There were no incident-specific, quantitative exposure A mathematical model was developed to estimate the air data available. In two incidents documented by CDHS, flight levels of permethrin during and immediately after the attendants were exposed to the aircraft cabin 45 min. (1 case) pesticide application. A complete description of the to two hours (10 cases) after a Residual application was methodology for the model is presented in Appendix A.
completed. The precise time between disinsection and flightattendant exposure could not be determined for the thirdincident (1 case). Of 12 flight attendants who became ill, four detected odor at the time of their exposure. For one incident(involving 10 flight attendants), it was reported that pesticide residues were visible on aircraft cabin surfaces.
Of 17 flight attendants with a reported illness, six completed interviews, eight declined participation, and threecould not be reached. CDHS interviewed eight employer A description of the sequence of the Residual disinsec- representatives, and five employee representatives from the tion work process is presented in Table III.
Association of Flight Attendants (AFA). Employer repre-sentatives included two of three industrial hygienists whocollected the employer exposure data, and other personnel responsible for implementation of the aircraft disinsectionprocedures. CDHS obtained symptom data for 15 flight The Residual disinsection process involved spraying the attendants through medical records and/or telephone inter- aircraft cabin and cargo hold with 34.4 liters (L) of a solution of 2.2% by weight (w/w) permethrin (25:75 cis:trans), 0.8% TABLE I. Sources of Data, Medical Information, and Exposure Characteristics of Three Incidents of Pesticide Poisoning Due to Aircraft Disinsection(N ¼ 12 cases) Immediately upon boarding (N ¼ 7) Within 1hr. of boarding (N ¼ 2) Unknown (N ¼1) Medical diagnosis by a physician at office visit Pesticide exposure (N ¼ 1)Post-prolonged insecticide fume [sic]/ Unknown or not reported (N ¼ 9) Recent sinus Number of medical records reviewed by CDHS Time between completion of disinsection and air-conditioning system with recirculation Adherence to post-disinsection 1-hr. aircraft aStandardized severity classification criteria were applied to pesticide illness cases (NIOSH, 2005). For the 12 cases reported in this paper, 7 were classified as ‘‘moderatelysevere’ and 5 as ‘‘mild.’.
Unknown ¼ missing data.
organic solvent carrier, 1.4% nonoxinol 9 (an emulsifier/ Approximately, 29 L of the pesticide solution was applied surfactant), and 95.6% water. The pesticide solution was to the passenger and crew sections of the aircraft, and mixed by pouring 700 ml of the product (an emulsifiable the remaining 5.4 L was applied to the cargo hold. The concentrate) into each of two 16.5 L containers of water. The disinsection process was conducted by three applicators in pesticide solution was mixed and loaded outside the aircraft.
about 35–45 min. From zero to 15 min. after the Residual Next, it was poured into two types of application equipment: pesticide application was completed the aircraft was (1) ultra-low volume (ULV) spray-mist ‘‘Cold Fogging’’ ventilated (Table III). The minimum ventilation period applicators (Curtis DYNA-FOG Tornado ULV Model 2895 required by the employer was 1 hr. For one of the incidents with Model 3000 Flex Hose. P.O. Box 297, 17335 US 31, documented by CDHS (10 cases), the air conditioning system North Westfield, IN 46074-0297, USA) which were pulled was used for ventilation, and the aircraft was ventilated for at through the aircraft on wheeled carts; and (2) a hand-held least 1 hr. In this incident, air was re-circulated throughout sprayer (B&G Model 1010 with Trigger TEEJET valve and the cabin during the ventilation period. For the other two 808 fine sprayer, 6.4 ounces per minute. B&G Chemicals & incidents (2 cases), CDHS could not determine the type Equipment Co., Inc. Dallas, TX). The foggers were used for of ventilation used (i.e., natural ventilation and/or the air most surfaces (e.g., seats, walls, overhead compartments), conditioning system) or the duration of the ventilation period.
and the hand-held sprayer was used for the galleys, crew rest Following the ventilation period, the aircraft was towed to the (bunk) area, bathrooms, cockpit, carpet, and cargo hold.
gate, and the flight crew boarded the aircraft.
Pesticide Illness Due to Aircraft Disinsection TABLE II. Signs and Symptoms Among12 Flight Attendants* with Pesticide-Related Illness from Aircraft Disinsection *More than one symptom or sign may have been reported by one individual.
@ Sign or symptom related specifically to permethrin or generally to pyrethroid expo- sure reported in the published literature [Flannigan et al., 1985; He et al., 1989; USEPA,1999; Kolmodin-Hedman et al., 1982; Fuortes, 1999; Bradberry et al., 2005; Spencer Exposure control measures were: the employer’s disin- section protocol specified a minimum of 1 hr. of ventilation after the pesticide application, accomplished by opening the cabin doors and/or provided by the aircraft’s air conditioning system (up to a maximum of 11 air changes per hour (ACH)); and the pesticide application was performed by ground crew before flight attendants boarded the aircraft. No personal protective equipment was required, recommended, or in use by flight attendants. Flight attendant training regarding the procedure consisted of one page of information in the flight attendant’s manual and a fact sheet on the issue distributed by There were no environmental samples collected from the aircraft involved at the time that these incidents occurred.
The available data were limited to permethrin levels in 136 samples collected by the employer from these or similar aircraft (747 –400s) following the same Residual disinsec- tion procedures conducted at other times. Between April 1997 and May 2001, the employer health and safety staff collected 64 surface wipe samples (i.e., from arm rests, walls, floor runners), 23 pieces of fabric and materials (i.e., seat covers, carpet, blankets, headsets, tissues, paper towels), and 49 area air samples. The employer conducted the industrial hygiene evaluation to monitor flight attendant pesticide exposure and in response to flight attendants’ expressed health concerns related to aircraft disinsection. Aircraft tested by employer health and safety staff were reportedly selected based on convenience and were considered to be representative of typical conditions. Samples were collected from a total of 11 planes from 15 min. up to 28 hr. after the aircraft were disinsected in Sydney with 34.4 L of a 2.2% permethrin solution. In September 2001, four additional surface wipe samples were collected by a flight attendant from one aircraft subsequent to Residual disinsection.
Permethrin levels on surfaces, fabric, and materials (N ¼ 91) were highly variable, with six orders of magnitude difference between the lowest and highest levels (range 15– ¼ 589,313 mg/m2; median 1600 mg/m2)). Permethrin was detected on aircraft cabin surfaces up to 28 hours after the pesticide was applied. No samples were collected later than 28 hours after the pesticide application. Ninety-five percent of the samples of surface, fabric, and other materials were 1,596,104 mg/m2 permethrin or less. The highest level of permethrin (35,980,000 mg/m2) was measured on carpet associated with a visible residue on the cabin floor.
Nineteen of 22 air samples (86%) collected in the time period beginning at the completion of the pesticide applica- tion up to approximately four hours post-disinsection had detectable levels of permethrin (range 2.2–1040 micrograms per cubic meter (mg/m3)). The highest level of permethrin measured in air (1040 mg/m3) was in a sample collected during the period approximately 15–96 min. post-disinsection.
Permethrin was not present at levels above the limits of detection in any of the 27 air samples collected in the time period 3–28 hr. after disinsection (LOD for 33 samples ¼ 0.15 mg/m3; LOD for 16 samples was not reported).
The results of the model estimating the concentration of permethrin in the aircraft cabin air during the pesticide application (0–30 min.) and during the 45-min. period following the application are presented in Figure 1. Two scenarios were evaluated in the model: (1) no mechanical dilution ventilation was supplied to the aircraft cabin in the 45-minute period after the application ended (0 ACH); and (2) 11 ACH was supplied in the 45-minute period following the application. The model assumed: (1) a solution contain- ing 2.2% permethrin (w/w) was applied with a fogger in the cabin; (2) passenger cabin volume of 1,000 m3; (3) average cabin height of six feet; (4) equal permethrin mass in different intervals of particle diameter in the range 5–40 mm; (5) uniform emission during the 30-minute spray period; and (6) no ventilation whatsoever in the cabin during the application. The model accounted for the differential gravitational settling rates of particles with different aero- The permethrin concentration in the aircraft cabin at the end of the application was estimated to be 91,178 mg/m3, based on the mass of permethrin released over time, the cabin air volume, the gravitational settling rates of the different- sized particles containing permethrin, and the rate of ventilation in the aircraft cabin. Forty-five min. after the Pesticide Illness Due to Aircraft Disinsection Many, but not all, of the health effects experienced by the flight attendants were consistent with recognized healtheffects specific to permethrin or generally to pyrethroidexposure (Table II). In order to be considered a case, oursurveillance criteria require the presence of two health effects(signs or symptoms) that are consistent with the health effectsof the active pesticidal ingredient as reported in the peer-reviewed literature [NIOSH, 2005]. Individuals may exhibita wide variety of signs and symptoms following pesticideoverexposure. The flight attendants described in this paperwere exposed to a pesticide formulation that includedpermethrin, solvents, and a surfactant. Any of these con-stituents may have contributed to health effects, but therelative contribution of each component is not known. Somethe health effects reported by the flight attendants may alsobe caused by anxiety and be observed with mass psychogenicillness [Lessenger, 1992; Jones et al., 2000; Henningsenet al., 2003]. However, because a pesticide formulationcapable of causing the symptoms was present in all cases, FIGURE 1. Model of permethrin levels in aircraft cabin air during and 45 min. after anxiety and, mass psychogenic illness are unlikely explana- Residual disinsection (29 L of 2.2% permethrin applied). [Color figure can be viewed in the tions for the symptoms [House and Holness, 1997; Jones, online issue,which is available at www.interscience.wiley.com.] application was completed, the air concentration of perme- thrin was estimated to be 5988 mg/m3 if there was no supplied mechanical ventilation (0 ACH), and 1.6 mg/m3 if 11 ACHwere supplied to the aircraft.
The 12 cases of pesticide illness documented by CDHS are the first reports of acute adverse human responses toaircraft disinsection reported in the scientific literature.
CDHS’ documentation of these cases occurred because theworkers sought medical care in a state with an occupational health surveillance system, their physicians reported theillnesses as required by law, and CDHS had the mandate and The 12 cases documented in this report demonstrate that capacity to conduct a follow-up investigation to link the Residual insecticide applications can result in acute illness reported illnesses with the circumstances in which the among workers exposed to the aircraft cabin environment exposures occurred. This underscores the critical role of after disinsection. All 12 cases met the NIOSH definition public health surveillance as an early warning system to of work-related acute pesticide poisoning. The evidence identify unrecognized harmful exposures and health effects supporting the role of pesticide exposure in causing the and to formulate and disseminate prevention strategies. The illnesses in these incidents includes: (1) all of the illnesses documented acute illnesses from aircraft disinsection in this occurred shortly after the onset of pesticide exposure; (2) all report underestimate the magnitude of illnesses due to this of the illnesses were documented by a licensed health care procedure. According to self-reports collected and compiled practitioner; (3) all cases experienced recognized signs and/ by the Association of Flight Attendants (AFA), flight or symptoms of exposure to permethrin; and (4) illnesses attendants (and, in some cases, passengers and pilots) were documented in three separate incidents (Tables I and II).
reported symptoms consistent with exposure to pyrethroid These illnesses are also consistent with acute human health pesticides on 237 flights from August 1, 2000 to July 31, 2001 effects experienced by workers exposed to pyrethroids in (Association of Flight Attendants. Memorandum to Patrice other occupational settings [He et al., 1989]; in the seven- Sutton from Judith Murawski. September 13, 2002). Of year period 1998–2004, CDHS’ SENSOR program identi- these, 224 (95%) followed Residual spray applications.
fied 230 cases of work-related illness due to pyrethroid During the calendar years 2000 and 2001, there were 38 cases exposure in other non-aircraft work settings.
of ‘‘insecticide poisoning’’ among flight attendants based in Los Angeles as recorded on the employer’s illness and injury associated with disinsection may exceed occupational logs and reviewed by CDHS. Moreover, CDHS did not assess the pesticide exposures incurred by the applicators in Sydney.
Treated surfaces are also a pathway of exposure These workers may incur the highest exposures from this to pesticides used for disinsection. Residual disinsection procedure, depending on the presence, use, and efficacy of involves intentionally spraying virtually all of the physical measures implemented to control their exposures.
space in an aircraft, including surfaces and materials, seats, The true nature and extent of health impacts of carpets, and bunks, and leads to pesticide residues in the disinsection are unknown because notification regarding aircraft cabin. The non-incident-related employer sampling the exposures and surveillance measures to comprehensively data documented that highly variable surface levels of track the required data are lacking. In general, cases of work- permethrin were prevalent throughout treated aircraft up to related pesticide illness are seldom reported and verified, 28 hours post-disinsection, with the variability of residues because substantial barriers to reporting exist [Azaroff et al., partly due to the differential collection efficiencies among 2002]. An individual must recognize they have been exposed surface types and the lack of a standardized sampling method to a pesticide, know the signs and symptoms of pesticide [NAS, 2002]. Although, dermal uptake of pyrethroids is illness, and seek medical care. Flight attendants received reported to be relatively low [Ray, 1991], results of case minimal training regarding their pesticide exposure; and studies of indoor exposures to other low-volatility pesticides cleaners, caterers, mechanics, and other workers who indicate that direct skin contact with contaminated textiles routinely entered newly pesticide-treated aircraft (Table III) significantly contributes to total body exposure [Gebefu¨gi, were not recognized as being pesticide-exposed. Therefore, workers may not have made the connection between their These data demonstrate that Residual disinsection exposure and symptoms. The treating physician must also application process results in pesticide residues in the aircraft recognize and report the illness to a local health agency.
air and virtually all of its physical space. Pesticide illness can The signs and symptoms of pesticide-related illness may be result if exposure to a treated aircraft cabin occurs in the nonspecific, and, therefore, may be misdiagnosed. Workers’ absence of adequate control measures.
fear of employment-related retaliation also prohibits fullreporting.
Factors That Contributed toDocumented Cases Flight Attendant Exposure AssociatedWith Residual Disinsection The accepted strategy for controlling toxic workplace exposures is to first attempt to eliminate the generationsource, hazardous materials, and dangerous activities The highest permethrin level in cabin air documented [Burgess, 1994]. When pesticide use is not or cannot be by the employer in this investigation was 1040 mg/m3, eliminated, most techniques designed to increase safety measured over the 81-minute interval beginning 15 min. after focus on the isolation of the chemical from the worker Residual disinsection. In a study of Pre-Flight and Top-of [Keifer, 2000]. In contrast, Residual disinsection involves Descent aircraft disinsection applications, mean levels of placing flight attendants in a pesticide-treated workplace d-phenothrin in area samples measured over the period with few industrial hygiene measures to minimize exposure including the spraying operation and a time of 40 min.
and no egress from the treated area.
afterwards were in the range of 133–1203 mg/m3 [Berger- Control of flight crew pesticide exposure in general, and Preiss et al., 2006]. WHO estimates that Pre-Flight and specifically for these 12 cases, relied exclusively on the Top-of-Descent disinsection results in a momentary maximal degree and duration of post-disinsection aircraft ventilation.
concentration of permethrin or d-phenothrin in aircraft air of The mathematical model illustrates the influence of the air 7000 mg/m3, with a considerably higher concentration close exchange rate and duration of ventilation on the amount of to the nozzle of the spray can, and a rapid drop in the con- pesticide residues in the air (Fig. 1). Other factors such centration after the spraying [WHO, 2005].
as equipment leaks [Llewellyn et al., 1996], application These data on flight attendant exposure are one to equipment that is not calibrated, and ambient temperature two orders of magnitude higher than maximum personal air and humidity will impact the distribution of pesticide levels monitoring exposure levels of workers in a variety of other on surfaces and in the air within and among treated aircraft.
settings where permethrin is used [Kolmodin-Hedman et al., Prior to these incidents, the employer had taken steps to 1982; Edling et al., 1985; Llewellyn et al., 1996]. This improve the safety of the required procedure by establishing a qualitative comparison illustrates the relatively high expo- minimum 1-hr. post-application ventilation period. However, sure levels potentially incurred by flight attendants on aircraft the exclusive use of the ventilation system at maximum where disinsection takes place, and that passenger exposure capacity was not specifically mandated in writing (Table III), Pesticide Illness Due to Aircraft Disinsection and there were no quality control or other requirements to chemical is used in practice. It is therefore imperative to document that after every application at least 1 hr. of such gather workplace data to validate assumptions related to occupational exposures, and to identify and consistently In one incident (10 cases), the required one-hour of implement measures capable of protect the health of exposed ventilation using the air conditioning system was implemen- ted, and the flight crew boarded the aircraft 2 hr. after theResidual application was completed. Despite these mea-sures, some of the 10 flight attendants observed pesticide residues and/or detected odor. The only deviation fromstandard procedures identified by the employer in this There were important limitations to this investigation.
incident was during the ventilation period, cabin air was re- Factors not identified by CDHS may have contributed to circulated, instead of being supplied with 100% fresh air.
these illnesses. Our understanding of the Residual disinsec- However, the Residual pesticide application results in tion procedure at the time of these incidents was based on aqueous, spherical particles in the range of 5 mm or greater, information pieced together from the employer’s data and virtually all of the particles are likely to be removed by (i.e., written documentation of the procedures, audits, air the HEPA filters present on a 747-400 aircraft. Therefore, re- monitoring reports, and a video of the standard procedure), circulating the aircraft air did not contribute to a significant incident-specific medical records and other illness reports, increase in flight attendant exposure. These 10 cases indicate and interviews with flight attendants and employer staff with that, although the standard (1 hr) ventilation procedures in-depth, first-hand knowledge of the procedure and/or were likely to have reduced flight attendants’ exposures, the incidents. Although the employer confirmed that CDHS’ procedures were not fully effective. For the second incident, process description was accurate, as in any workplace, only the flight attendant boarded the aircraft 45 min. after the the workers who actually applied the pesticide had direct application, before the required one-hour ventilation period.
knowledge of what occurred. Therefore, we cannot rule out There was insufficient information to assess what additional that other, unrecognized factors (e.g., the pesticide was not factors may have contributed to the flight attendant’s illness mixed or applied according to procedures) contributed to these illnesses. This seems unlikely to have occurred for at We conclude that inadequate post-disinsection aircraft least one incident (10 cases). In this incident, the employer ventilation procedures and a lack of quality assurance measures contributed to the documented adverse health The amount of pesticide exposure incurred by flight impacts. Conditions for adverse health impacts may have attendants in the incidents reported by CDHS is not known.
been present on other flights not reported to CDHS.
There were no incident-specific personal-exposure monitor- Employer records of non-incident-specific sampling data ing data for the cases. However, the existing samples were document that the ‘‘disinsection application crew did not all collected in real-time, under representative workplace always follow established procedures’’ and that ‘‘natural conditions, include a very large number of samples from ventilation is insufficient to assure that all damp surfaces are multiple aircraft over time, and virtually all were collected by industrial hygiene professionals. As such, the samples Worker illness may have been exacerbated because provide evidence of the magnitude and route of flight flight attendants were unable to remove themselves from attendant exposure, which occurred via inhalation and exposure and seek medical care in a timely way. The primary through contact with treated surfaces.
intervention in the case of a toxic exposure is to remove the Although we attempted to contact all flight attendants, affected individual from the area of exposure as soon as only 5 of 12 cases (42%) were interviewed by CDHS. Such possible [Lessenger, 1992]. Residual disinsection results in a low response rate is consistent with the interview rate unavoidable flight attendant exposure to a pesticide in a for a passive surveillance system and does not suggest a confined space (i.e., a relatively small, enclosed area with no systematic unidentified cause for low worker participation. In ready egress). Therefore, the most important treatment of any general, a limitation of passive surveillance systems is that toxic syndrome, interruption of exposure [Fuortes, 1999], is there can be a time delay between when an incident occurs, and when reports are received, processed, and investigated.
WHO recommendations for disinsection are based on For two of three incidents (11 cases), 6–8 months had elapsed two health-related assumptions: (1) the human toxicity of between the time of the incidents and the interviews. For the permethrin is low; and (2) the conditions of use will result in third incident (1 case), 3 weeks had elapsed between the time exposures to concentrations too low to cause acute illness of the incident and the interview, which in this case was [WHO, 1985a,b, 1995, 2005]. The findings of this investiga- completed successfully. The delay in interviewing the tion illustrate that relatively ‘‘low-toxicity’’ chemicals can workers did not introduce recall bias into the case classifica- result in hazardous exposures as a consequence of the way a tion. All 12 cases sought medical care from a licensed health care provider within 2 days or less after the onset of Until non-toxic alternatives are adopted or sanctioned by symptoms. For all 12 cases the medical information recorded countries that require disinsection, airline employers should at the time of the incident served as the main source of take steps to mitigate flight attendant pesticide exposure. It is data regarding health effects. Other factors that may have important to note that, although these interim measures are influenced the response rate were that the interviews were expected to increase protection for potentially exposed solicited by telephone, and the workers had no previous individuals, they may not be entirely effective in preventing contact with CDHS and therefore had not established a basis exposure to pesticide formulations. Airline industry employ- of trust with us. Finally, workers were difficult to reach ers should: educate all potentially exposed workers about the because they lived in other states and had irregular work- hazards of aircraft disinsection; restrict entry for all workers schedules. In general, fear of job loss is a barrier to worker to the aircraft cabin for at least 4 hr. after disinsection; participation in occupational health investigations. We are implement, document, and enforce maximal ventilation unable to identify which, if any, of these potential barriers procedures on every treated aircraft; conduct industrial to participation impacted the response rate.
hygiene sampling to validate the efficacy of a restricted entry Finally, our assessment did not take into account the interval and maximal ventilation procedures in mitigating potential long-term effects of repeated low-level exposures airborne exposures, wet surfaces and/or puddles, or other to pyrethroid pesticides. One study of 33 self-selected, avenues for dermal exposure; institute quality control pesticide-exposed flight attendants, reported that nearly half measures for every pesticide application, including a policy had three or more abnormal neurobehavioral functions of not boarding aircraft that lack written documentation of [Kilburn, 2004]. Permethrin is considered a potential carci- compliance with pesticide exposure control measures; seek nogen by the USEPA [USEPA, 1997], and the International permission from the relevant national quarantine authorities Agency for Research on Cancer states there is inadequate to cease spraying pesticides in the crew rest area (bunk room), evidence in animals to classify the carcinogenicity of an area that encompasses both minimal air flow and potentially maximal contact with treated surfaces; notify inadvance passengers who may be exposed to a pesticide- treated aircraft of the procedure and the potential health risks;schedule flights to countries that require disinsection so that The 12 cases of pesticide illness documented in this the number of aircraft treated is minimized; and initiate investigation demonstrate that Residual insecticide appli- active illness surveillance among exposed workers and cations can result in illness among workers exposed to the aircraft cabin environment after disinsection. The documen-ted acute illnesses likely underestimate the magnitude of illnesses due to disinsection. The public health impact ofResidual disinsection also includes other workers who pilot, The authors gratefully acknowledge the essential clean, service, and maintain the aircraft, and the passenger contribution of the flight attendants to this study. We also population. The conditions of use (i.e., the aerosol applica- recognize and appreciate the vital role that the employer and tion of a pesticide in a confined space) significantly Judith Murawski of the Association of Flight Attendants contributed to the human health hazard of Residual played in the investigation. Susan Edmiston and Louise disinsection. Therefore, the replacement of permethrin with Mehler of the California Department of Pesticide Regulation another chemical alternative would not eliminate the health provided helpful review of a draft of the CDHS report on which this paper is based (CDHS, 2003). NIOSH funding The prevention of vector-borne diseases remains provided crucial support to this investigation.
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CðtÞ ¼ ½G=ðlambda1 à VŠ  ½1 À expðÀlambda1  tŠ ð3Þ where V is the passenger cabin volume (1000 m3) and t is timein min. This equation holds from t ¼ 0 to t ¼ 30 min.
The total airborne concentration at any time is the sum of the concentrations for the 35 respective bins. At the endof spraying (t ¼ 30 min), there is some total concentration.
The purpose of the model was to estimate the air levels The model assumes the ventilation system was running for of permethrin during the 30-minute application period 45 min. and provided Q m3/min of effective ventilation and during the 45-minute period after the application is (11 ACH). For the Q value used, compute lambda2 ¼ Q/V per completed. Using the model, two scenarios are evaluated: (1) no mechanical dilution ventilation is supplied to the In each bin, there was some initial concentration C (zero) aircraft; and (2) maximal dilution ventilation (11 air changes equal to the C(30 min) value at the end of the spraying. In per hour) is supplied for 45 min. following the pesticide each bin, the decay in concentration (ug/m3) is computed by CðtÞ ¼ C zero  expðÀ½lambda1 þ lambda2Š  ðt À 30ÞÞ a solution containing 2.2% permethrin (w/w) is applied This equation holds from t ¼ 30 min to t ¼ 75 min., where t ¼ 0 is the start of the spraying.
equal permethrin mass in the different particle sizes in The total airborne concentration at any time is the sum of the concentrations for the 35 respective bins.
uniform emission during the 30-minute spray period; Note: A lower average cabin height would increase the no ventilation whatsoever in the cabin during the rate of settling. Putting more of the mass in smaller particles would increase the airborne mass concentration, whileputting more of the mass in larger particles would decrease *CDHS requested detailed information on particle size dis- tribution from the manufacturer but data were not provided.
To begin, the model divides the particles into small diameter bins and uses the midpoint values. For example,there was a 5–6 mm bin (midpoint 5.5 mm), a 6–7 mm bin TABLE A1. Predicted Air Concentration of Permethrin (mg/m3) by Quantity (midpoint 6.5 mm), and so forth up to the 39–40 mm bin Applied and byAircraft Ventilation Status (midpoint 39.5 mm). For each bin, the midpoint diametervalue is used to compute the terminal settling velocity (m/ min) for particles in that bin by: VTS ¼ .0018 Â (D^2), where the diameter D is in mm. This equation holds for a sphere of unit density (water), which is essentially what the pesticidesolution is. A slip correction factor was not used because its Quantity of pesticide Permethrin concentration effect on VTS is negligible for particles with aerodynamic diameters greater than 5 mm. The effective or average height H (in m) of the passenger cabin is assumed to be 1.83 m (6 ft).
lambda1 ¼ VTS=H per minute for the particles in that bin 34.4 L of a 2.2% solution of permethrin is applied to the aircraft. Approximately, 29 L is The model assumes that each of the 35 bins contained applied to the cabin, and 5.4 L is applied to the cargo hold. It is assumed that the 1/35 of the permethrin mass applied, and that the mass was application to the cargo hold does not impact air quality in the cabin.

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