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involving pregnant women, two of whom reported having subsequent stillbirths. Thirty-five of the remaining pregnant women were followed—up 9 mo after the epidemic; no additional stillbirths were found. To control the epidemic, it was necessary to embargo on July 4 and to destroy all watermelons in the state on July 7 and to effect a field certification program. The epidemic and the costly resultant control measures illustrate the difficulties in assuring the safe use of the most potent pesticide. The use of pesticides is controlled by an elaborate set of crop specific regulations. State and federal regulators use laboratory tests of produce samples to insure that regulations are followed. When inadvertent or illegal applications of pesticide occur in a particular crop, there is no system that guarantees that the public will not be exposed. For most pesticides, the effects may not be dramatic, but when a potent pesticide appears in a widely eaten commodity, the impact on health and the institutions that are designed to protect it can be devastating. This paper describes the course of one such event.

ON JULY 3, 1985, the Oregon Department of Health notified the California Department of Health Services (CDHS) of several cases of possible pesticide illness related to consumption of watermelons that were thought to have been grown in Arizona.1,2 At 4:00 A.M. on July 4, a 62-y-old woman on digoxin therapy was treated at a Lake County California, emergency department for hypotension, severe bradycardia (31 beats per minute [bpm]), atrial fibrillation, diaphoresis, vomiting, diarrhea, lacrimation, salivation, and muscle twitching. She had eaten watermelon about 30 min earlier. Her symptoms resolved following treatment with atropine. Two other family members who had consumed the same watermelon were also ill and had similar though milder symptoms. The treating physician notified the San Francisco Bay Area Regional Poison Control Center, which subsequently notified CDHS.

Later on the morning of July 4, Oregon officials reported to CDHS that aldicarb sulfoxide (ASO), a toxic degradation product of aldicarb, had been detected in several of the melons related to illness episodes in that state and that the origin of the melons was, in fact, from California.1,2 Aldicarb, CAS No. 116–06–3, is a cholinesterase-inhibiting carbamate pesticide that is not registered for use on watermelons in the U.S. but commonly used on citrus, cotton, potatoes, peanuts, and soybeans. Within 2 h, calls to 10 California poison control centers, 20 selected emergency departments, and 1 county health department had identified an additional 12 presumed cases of pesticide illness related to consumption of watermelons. This included a group of 4 individuals in Bakersfield who had eaten a striped melon purchased at a roadside stand, a group of 6 individuals who had eaten a striped melon from a Los Angeles-area supermarket warehouse, and 2 individuals in the San Francisco Bay Area who had eaten green melons purchased at different retail stores. These illnesses were investigated by state and local health officials, and arrangements were made for obtaining watermelon samples.

Just prior to noon on July 4, statewide media advisories were issued that warned against eating watermelons, and an embargo was placed on the sale of watermelons throughout California. Usual product recall mechanisms were inoperative because the day was a national holiday. By late afternoon on July 4, case investigations and tracking of sources of melons back through the distribution chains had implicated a single Kern County shipper in several, but not all of the episodes. Subsequently, in the melon from the first known California case, ASO was found at 2.7 parts per million (ppm). The embargo remained in effect for the next 3 d.

On July 7, all watermelons in retail outlets or in the chains of distribution were destroyed because it was impossible to distinguish ASO-contaminated melons from melons free of ASO. A field certification program was implemented on July 10, and the embargo was lifted. Surveillance after that time identified only one further illness episode in California associated with a melon that tested positive for ASO. Product certification was conducted by the California Department of Food and Agriculture (CDFA) and involved testing composite samples of melons from fields for aldicarb and its metabolites. Melons from fields that tested negative were labeled by CDFA to certify that they had been cleared.


Commencing late on the morning of July 4, the public was advised through the mass media to report any watermelon-associated illness to their local health department. An active surveillance network set up by CDHS on July 5 involved (a) daily calls to California’s 10 regional poison control centers and selected emergency departments, (b) daily contact with all local health departments in California, and (c) periodic calls to several western states and the western provinces of Canada. Local health departments were asked to complete and return an illness report form (described below) to CDHS for all cases reported to them. They were also asked to periodically call selected hospital emergency departments within their jurisdiction so as not to miss illnesses severe enough to require emergency treatment or hospitalization.

The CDHS illness report form and a case-definition algorithm were developed based on the expected cholinergic symptoms resulting from ingestion of aldicarb (Table 1). The case definition divided illness reports into three categories: (1) probable, (2) possible, or (3) unlikely, depending on timing of symptom onset, nature and severity of

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