For the five-year time period of 2001 through 2005, a total of 407 cases fit our case definition (205 from Washington and 202 from Oregon). Cases peaked seasonally, with the largest number of cases occurring in the summer months. The demographics of people meeting the case definitions by illness severity are presented in . Cases were categorized as follows: definite, 64 (16%); probable, 45 (11%); and possible, 298 (73%). Approximately one-quarter of total cases were work-related. Females accounted for a slightly higher proportion of case subjects (55%) than did males (); however, the IRRs for males vs. females for all age categories were not significantly different (data not shown). The median age of people meeting the case definition was 37.6 years (range of 7 months to 99 years of age); the median age by illness severity was 36.6 years of age for people in the low severity category and 41.8 years of age for people in the higher severity categories (including moderate and high severity as well as death) (data not shown). The highest proportion of people meeting the case definition were in the age ranges of 40 to 49 years (n=72, 19%) and 30 to 39 years (n=71, 19%).
Demographic data by severity category for 407 cases of acute pyrethrin or pyrethroid pesticide poisoning, Oregon and Washington, 2001–2005
Illness severity is presented in . Most cases were low severity (92%). One death occurred; this case is included in the moderate/high category (8%). Severity (low vs. moderate/high) did not differ by age group, gender, year of event, or work-related status. Severity did differ by state, with Washington more likely than Oregon to have moderate or high severity cases (p=0.002). Case classification differed by illness severity, with a much larger proportion of definite cases having moderate or high illness severity (p<0.0001).
Overall, the incidence rate of acute pyrethrin or pyrethroid poisoning was significantly higher in Oregon compared with Washington (IRR=1.70, 95% CI 1.40, 2.07) (). Both states had significant increases in poisoning rates from 2001 to 2005 (Mantel-Haenszel Chi-square, p=0.049 for Oregon and p<0.001 for Washington).
Number of pyrethrin/pyrethroid poisoning cases among Oregon and Washington State residents, incidence rates, and incidence rate ratios, by year, 2001–2005 (n=407)
For active ingredients, type I pyrethroids were the most commonly reported for all severity groups (n=221, 41%) (). The most commonly reported type I pyrethroid was permethrin (n=83, 16%), followed by tetramethrin (n=46, 9%). Pyrethrins were the second most common type of active ingredient for all severity groups (n=172, 32%). Type II pyrethroids were the least common type of active ingredient reported for all severity groups (n=141, 26%). The most commonly reported type II pyrethroid was cypermethrin (n=38, 7%), followed by cyfluthrin (n=28, 5%). When case severity was classified into two groups (low vs. higher) and compared with the active ingredient category, we found that individuals whose cases had moderate, high, or fatal outcomes were more likely to be exposed to type 1 pyrethroids compared with those whose cases were classified as low severity (p=0.0117). also shows that in the majority of cases, individuals were exposed to low toxicity products, based on U.S. Environmental Protection Agency (EPA) toxicity ratings.
Frequency of active ingredients and pesticide toxicity category for 407 cases of pyrethrin or pyrethroid pesticide exposure by case severity grouping, Oregon and Washington, 2001–2005
lists clinical signs and symptoms reported by people with cases of acute pesticide poisoning from pyrethrins or pyrethroids. The most common category of signs or symptoms reported was respiratory (n=210, 52%), followed by neurological (n=162, 40%), and gastrointestinal (n=134, 33%). The most common individual signs or symptoms are shown following each major division in .
Clinical signs and symptoms reported by Oregon and Washington State residents exposed to pyrethrin or pyrethroid pesticides, 2001–2005 (n=407)
For reported preexisting conditions, 71 people had allergies (17%), 60 had asthma (15%), 10 had multiple chemical sensitivity (3%), and four were pregnant (1%) (). There was a significant association between the presence of any preexisting condition and illness severity (p=0.035), with a larger proportion of those with preexisting conditions having moderate or high severity illness.
Frequency of reported preexisting conditions for 407 cases of exposure to pyrethrin or pyrethroid pesticides by case severity grouping, Oregon and Washington, 2001–2005a
For route of exposure to the pesticides, the predominant method was inhalation (63%), followed by skin (37%), eye (28%), and ingestion (8%). More than one exposure route could be reported for each case. There was no significant association found between route of exposure and illness severity (data not shown).
Most exposures (74%) were not occupational exposures (, , , and ). For the 293 nonoccupational cases, 136 (46%) occurred when the individual was mixing, applying, or otherwise handling the pesticide. Approximately half became exposed during routine living activities not involving handling of the pesticide (145 of 293, 49%) (). The most common equipment used for nonoccupational cases was a pressurized can or “bug bomb” (103 of 293, 35%) (). The vast majority of nonoccupational cases were residential exposures (255 or 293, 87%) ().
Activity of pesticide-exposed individual by work status, Oregon and Washington, 2001–2005 (n=397)a
Equipment or application method of pesticide by exposed individual's work status, Oregon and Washington, 2001–2005 (n=397)a
Location of exposure by work status of individuals exposed to pyrethrin or pyrethroid pesticides, Oregon and Washington, 2001–2005 (n=397)a
For work-related cases (26%) (, , , and ), 71% of people were exposed while doing their normal work duties and were not handling pesticides (74 of 104) (). As with nonoccupational cases, the most common equipment or application method was a pressurized can or aerosol bomb (38 of 104, 36%) (). In contrast with nonoccupational cases, people in the occupational cases were most likely to be exposed at a non-manufacturing facility, such as a retail nursery or office building (41 of 104, 39%). The second most commonly reported location for occupational exposures was a private residence (22 of 104, 21%) (). More than half (13 of 22, 59%) of the workers exposed at residences were licensed pesticide applicators, and another third (7 of 22, 32%)—five emergency responders and two reporters—were exposed during a single incident (data not shown).
Pesticide-related illness may result in time lost from work, school, or regular activities. Where lost-time status was known, 13% (31 of 242) of people with low severity cases reported one day or more of lost time; for those with moderate to high severity cases, the percentage increased to 52% (14 of 27). Because days of lost time are part of the severity ranking, it is not surprising that lost-time status was significantly associated with severity grouping (p<0.0001) (data not shown).
The following two cases, one from Oregon and one from Washington, are presented to illustrate the potential severity of pyrethrin or pyrethroid poisoning.
In 2005, a licensed pesticide applicator utilized a crack and crevice technique with a mixture of two types of pesticide: a pyrethroid (esfenvalerate, 3.48%) and pyrethrins (1.00% formulated with piperonyl butoxide and N-octyl bicycloheptene dicarboxidmide) for pest control on the interior of a residence in Florence, Oregon. An exterior application of a permethrin was made after the interior application. Upon reentry into the home, approximately three and a half hours after the interior application, one of the residents, an elderly woman with a history of heart disease, experienced acute respiratory symptoms and cardiac arrhythmia. Resuscitation attempts were unsuccessful, and the woman died at the scene.
The woman's spouse, two neighbors, and five responders to the incident (three emergency medical technicians and two police officers) experienced less severe, but similar upper respiratory symptoms (dyspnea, mucous production, throat constriction, and coughing). Their symptoms resolved shortly after they exited the home or within several hours. The spouse of the deceased woman was hospitalized overnight for observation. Upon review by Oregon's Pesticide Analytical Response Center, it was concluded that the cardiac arrhythmia was most likely caused by respiratory distress, which “resulted from inhalation exposure to the pesticides that were applied to the interior of her home.” This conclusion was in agreement with the Lane County Medical Examiner, who concluded that her death was due to “sudden cardiac arrhythmia following exposure to pyrethroid insecticide in an elderly woman with significant heart disease.”15
In June 2005, a 53-year-old man with a history of reactive airways disease and allergies to multiple common therapeutic drugs sprayed his car with an aerosol house and garden insecticide containing the type I pyrethroids phenothrin and d-cis,trans allethrin. He left his car with the windows closed until the following day. He did not clean surfaces or thoroughly ventilate the car before driving it into town the next day. He reported that difficulty breathing developed within an hour of reentering the car. His symptoms progressed to coughing and respiratory congestion.
Over the next five days, he reported intermittent fever, increasing congestion with productive cough, and persistent wheezing. He was seen by his primary care provider five days after his exposure and was prescribed steroids and antibiotics in addition to his normal inhalers. When he did not improve, he was admitted to the hospital 10 days after his exposure for failure of outpatient treatment. On admission, he was noted to have bilateral and diffuse rhonchi and expiratory wheezing. He was treated with intraveneous steroids, antibiotics, bronchodilators, and oxygen supplementation as needed. He was discharged three days later in stable condition with a diagnosis of severe asthma exacerbation. Other ingredients identified on the product material safety data sheet were 0.1% sodium nitrite, 3%–7% isoparaffinic hydrocarbon solvent, 3%–7% isobutane, 5%–10% propane, and 70%–80% water. There was no mention on the label that the insecticide product could exacerbate asthma or other respiratory conditions.