Risk factors for systemic illnesses following agricultural exposures to restricted organophosphates in California, 1984-1988.

Organophosphate (OP)-related systemic illnesses reported to the Worker Health and Safety (WH&S) Branch, and restricted OP-related agricultural use data reported to the Information Services Branch at the California Department of Food and Agriculture (CDFA) (now CAL-EPA) during 1984-1988 were used to assess factors associated with OP-related systemic illnesses. Counts of OP-related systemic illnesses (numerator), relative to OP-related use data (denominator), such as pounds applied, number of applications, and acres treated (pounds applied/acres treated), were analyzed by crop treated, season of application, method of application, geographic region, and by specific OP applied. A Relative Illness/Use Ratio (RIUR) was calculated by Poisson regression. The highest risk of systemic illness was associated with OP applications to fleshy fruit (mainly fruit trees) compared to all other crops combined (RIUR = 2.9, 95%CI = 2.2-3.9) using pounds applied in the denominator, followed by vegetables and melons (RIUR = 1.9, 95%CI = 1.4-2.4). Air applications resulted in higher RIURs for systemic illness than did ground applications (RIUR = 2.1, 95%CI = 1.7-2.5). Specific OPs that showed significantly elevated RIURs for systemic illness when compared to other OPs were Mevinphos (RIUR = 5.8, 95%CI = 5.0-6.8), Demeton (RIUR = 4.3, 95%CI = 2.6-7.1), Oxydemeton-Methyl (RIUR = 3.8, 95%CI = 3.0-4.9), Methamidophos (RIUR = 1.6, 95%CI = 1.2-2.0) and Azinphos-Methyl (RIUR = 1.3, 95% CI = 1.1-1.6).

Monitoring the pesticide-exposed worker.

Cholinesterase inhibitors-the organophosphates and the carbamates-are the most acutely toxic and widely used insecticides. They also comprise the only group of pesticides for which state laws exit requiring worker monitoring. This chapter focuses on cholinesterase monitoring, with attention to available assays and testing kits.

Skin reactions to pesticides.

Skin disease is the second most common type of occupational illness. This chapter reviews the important concepts in pesticide-related dermatoses, first by examining two case studies and then by describing the major fungicides, insectides, herbicides, and fumigants associated with skin disease.

Determinants of disability in illnesses related to agricultural use of organophosphates (OPs) in California.

Organophosphate (OP)-related illness data reported to the Worker Health and Safety Branch (WH&S) at the California Department of Food and Agriculture (CDFA, now Cal-EPA) in the years 1984-1988 were examined. Eight hundred and seventy-eight cases with systemic illness and 199 cases of skin disease or eye injury were identified. Systemic cases were divided into two outcome groups: (1) "severe," disability and/or hospitalization days (n = 361), and (2) "mild," no disability or hospitalization days (n = 372). For the remainder (n = 145) or 16.5% of the cases, illness severity could not be determined. Using multiple logistic regression, independent predictors of "severe" illness were identified among the systemic cases. Workers coming in contact with OP residue on commodities or in the field ("exposed to residue" or ER) (OR = 4.6, 95% CI = 3.03-7.07) and mixer/loaders/applicators (MLA) (OR = 4.1, 95% CI = 2.72-6.07) were at significantly increased risk of severe illness when compared with cases exposed to OP application drift. Cases with a Spanish surname were also at increased risk of severe illness (OR = 1.8, 95% CI = 1.25-2.73). Increased numbers of OPs per exposure were also associated with severe illness (p < 0.001). Among cases who were exposed to only one OP, severe systemic cases were more likely than mild systemic cases to be associated with exposure to diethyl than dimethyl compounds (OR = 1.6, 95% CI = 1.09-2.38). Severe systemic cases were also more likely than severe skin/eye cases to be associated with exposure to OPs with high toxicity (OR = 5.5, 95% CI = 2.42-12.60) and with exposure to diethyl groups (OR = 4.8, 95% CI = 1.90-12.00). These findings suggest that reducing exposure to OP residues, to OPs with diethyl groups, and to multiple OPs, and exposure during mixer/loader/applicator activities would reduce the risk of OP-related illness.

Acute pesticide morbidity and mortality: California.

The California Pesticide Illness Surveillance Program collects, investigates, abstracts, and records reports received from physicians. A minority of the reports are received through the county health officers who are notified by physicians under a state requirement for reporting pesticide-caused conditions. Most of the cases are identified by review of workers' compensation records. All the cases identified are investigated by the agricultural commissioners of the counties where exposure occurred. The investigation reports are reviewed and abstracted by staff of the Worker Health and Safety Branch of the California Department of Pesticide Regulation, California Environmental Protection Agency (Cal/EPA). The crucial determination is assessment of the degree of relationship between the exposure and subsequent disease: definite, probable, possible, unlikely, or unrelated. In most years, the number of cases investigated has been between 2,500 and 3,000. Excluding antimicrobials, the number of cases found after investigation to have a definite, probable, or possible relationship with pesticide exposure has ranged from 970 (in 1989) to 1,372 (in 1988). Cases involving antimicrobials rarely were reported prior to 1987. In that year, surveillance staff began reviewing workers' compensation records personally, with the specific goal of identifying antimicrobial cases. Since then, antimicrobials have been found to account for 746-813 cases annually, primarily involving splashes and squirts to the eye and inhalation of fumes or vapors. Numbers of case reports from agricultural situations have varied irregularly, driven by small numbers of episodes concerning multiple individuals. Variability in numbers of cases involving the skin has depended almost entirely on variation in numbers of field worker dermatitis. The most common situation for field worker dermatitis has been summer work in table grapes grown in the southern San Joaquin valley. In the two years since reentry intervals for the acaricide propargite were lengthened, there have been no more major clusters of field worker dermatitis. Although the cases collected by the surveillance program are predominantly occupational, because of dependence on workers' compensation for case identification, most recorded deaths are nonoccupational. Nonoccupational fatalities include suicides, mistaken ingestion of pesticides (especially if stored in food containers), and entry into structures being fumigated. Occupational deaths are less common and more varied. The circumstances of each reported occupational death are summarized above.

Subacute poisoning with phosalone, an organophosphate insecticide.

An illness characterized by weakness, dizziness, and gastrointestinal symtoms was identified among a crew of 30 migrant field-workers employed by a grape grower in Madera County, California, during August 1987. The onset of symptoms occurred between August 24 and August 30 and a median of 9 days from the date of first employment. The first crew member sought medical treatment on August 26, and 10 crew members were admitted to hospital between August 27 and August 30. For most workers, gastrointestinal and constitutional symptoms resolved shortly after admission, but 4 patients had episodes of severe sinus bradycardia persisting for several days. On the day of admission, transient atrioventricular dissociation developed in 2 persons. Interviews with 16 crew members not admitted to the hospital identified only 1 additional worker ill with gastrointestinal symptoms, but all 16 had moderate to severe inhibition of both plasma and red blood cell cholinesterase. Four other workers who were tested but not interviewed also had cholinesterase depression. The crew had had exposure since August 19 to the organophosphate insecticide phosalone, which was last applied to the vineyard on July 21, or 29 days earlier. Although this is the first report unequivocally linking phosalone to field-worker poisoning, the delayed onset and nonspecific nature of the symptoms associated with subacute poisoning may have hindered the recognition of previous similar episodes.

Chloracne associated with employment in the production of pentachlorophenol.

To evaluate the association between exposure to pentachlorophenol (PCP) and the occurrence of chloracne, we studied the medical and personnel records for individuals employed in the manufacturing of PCP. Forty-seven cases of chloracne were identified among 648 workers (7.0%) assigned to PCP production at a single plant between 1953 and 1978. The annual incidence rate varied considerably, ranging from 0 (in 1953) to 1.46 (in 1978). No linear trend in the risk of chloracne was observed with the duration of employment in the pentachlorophenol department. Workers with a documented episode of direct skin contact with PCP had a significantly increased risk of chloracne compared with workers who did not have a documented episode of direct skin contact (cumulative incidence ratio = 4.6; 95% confidence interval 2.6-8.1). Our results confirm that chloracne is associated with exposure to PCP contaminated with hexachlorinated, heptachlorinated, and octachlorinated dibenzo-p-dioxins and dibenzofurans.

Occupational vitiligo due to unsuspected presence of phenolic antioxidant byproducts in commercial bulk rubber.

We investigated the occurrence of cutaneous depigmentation (vitiligo) among employees of a company that manufactured hydraulic pumps. The interiors of these pumps were injection-molded with rubber. We identified a small but significant cluster of vitiligo cases among a group of employees who frequently handled the rubber used in this injection molding process. Although none of the additives specified in the rubber formulations was a phenolic or catecholic derivative, known to be potential causes of chemically induced vitiligo, gas chromatographic analysis identified a para-substituted phenol (2,4-di-tert-butylphenol, DTBP) in solid samples of the most frequently used rubber. Surface wipe analysis confirmed that workers could be exposed to DTBP from simple handling of the rubber. We subsequently established that the solid bulk rubber used as the base in these stock rubber formulations contained both DTBP and smaller quantities of p-tert-butylphenol. Both had formed as unsuspected byproducts during chemical synthesis of two antioxidants added to the solid bulk rubber by a major rubber supplier. We conclude that the unsuspected presence of potential chemical depigmenting agents in solid bulk rubber, from which industrial rubber products are formulated, may contribute to the occurrence of occupational vitiligo, and that a simple review of ingredients in rubber formulations is inadequate to detect their presence.

Distribution of lost-work-time claims for skin disease in California agriculture: 1978-1983.

In order to identify California agricultural workers at high risk for occupational skin disease, we evaluated the distribution of 2,722 claims for lost-work-time skin conditions reported between 1978 and 1983 by Standard Industrial Classification (SIC) and source of illness. In the overall work force, cases were most frequently attributed to plants (52.1%), chemical exposures (20.4%), and food products (12.5%), but considerable variation occurred in the distribution of cases among the subdivisions of agriculture. The forestry subdivisions (SICs 081, 082, 084, and 085) had the highest rate (given as cases/10,000 employed) of claims for skin disease attributed to plants (53.5), but no cases due to other exposures. For chemical exposures, the highest rate of claims occurred in the horticultural specialities (SIC 018) subdivision (5.1), but this group also had a significant claims rate for plant-related skin disease (15.9). The highest claims rate for cases attributed to food products occurred in the vegetables/melons subdivision (4.7), but this group had claims rates for exposure to plants (3.8) and chemicals (2.8) that were nearly as high. Efforts to evaluate and prevent skin disease in agricultural workers should recognize the complex range of exposures to which this work force is subject.

Phytophotodermatitis from celery among grocery store workers.

We detected 19 cases of phytophotodermatitis during a cross-sectional epidemiological investigation of two Oregon grocery stores that were part of the same supermarket chain. Outdoor sunlight exposure during the workshift and tanning salon use were identified as risk factors; the most severe cutaneous reactions tended to occur among tanning salon users. Although both stores carried the same brands and varieties of produce, all 19 cases occurred among employees of one store, which had held a celery sale coincident with the outbreak, resulting in a quadrupling of the usual volume of celery sold. We found elevated psoralen levels in two of three celery samples obtained from the affected store; cutaneous provocation tests with trimmed surfaces of these celery samples produced phototoxic reactions. Preliminary experiments with one brand of celery have demonstrated psoralen levels as high as 25 micrograms/cm2 of trimmed surface. These observations suggest that clinical phytophotodermatitis among grocery store workers may be caused by healthy celery and results from a complex interaction of exposure variables, including ultraviolet radiation from tanning salon use, frequency of handling celery, celery brand, and sporadic elevation of psoralen content from environmental stresses.

Clinical confirmation of organophosphate poisoning of agricultural workers.

A group of 31 lettuce harvesters exposed to the organophosphate pesticide mevinphos presented to a local emergency room with moderate cholinergic symptoms and eye and skin irritation, with 22 of the subjects (76%) reporting three or more symptoms. None had baseline cholinesterase values, and plasma cholinesterase activity for all but two workers was above the lower limit of the laboratory normal range. None of the workers received antidotes and all were released for return to work. Twenty-nine workers sought additional care when symptoms persisted, and were followed by the investigators until 12 weeks after exposure. Plasma and red blood cell (RBC) cholinesterase increased until 14 days after exposure. Plasma cholinesterase was estimated to have been inhibited by an average of 15.6% (p less than 0.01), and RBC cholinesterase by 5.6% (p less than 0.01). These findings support the utility of sequential postexposure plasma cholinesterase analyses in confirmation of suspect organophosphate-induced illness when baseline values are not available.

Clinical management of field worker organophosphate poisoning.

A group of 16 cauliflower workers poisoned by residues of the organophosphate insecticides mevinphos and phosphamidon was followed in weekly clinics with interviews and determinations of plasma and erythrocyte cholinesterase levels. None had preexposure baseline values. Although six had initial erythrocyte cholinesterase values within the laboratory normal range, subsequent testing showed their erythrocyte activity had been significantly inhibited. While the most severe symptoms of the 16 subjects resolved after 28 days, their erythrocyte cholinesterase levels did not reach a plateau until an average of 66 days after exposure, after which most patients continued to report blurred vision, headache, weakness or anorexia. These findings support the view that the diagnostic utility of single cholinesterase levels is limited in the absence of baseline values.

Control of phosphonic acid and phosphonolipid synthesis in Tetrahymena.

The phosphonolipid content of the protozoan Tetrahymena pyriformis was increased by growing the organism on a medium containing increasing amounts of 2-aminoethylphosphonic acid. With levels of 0, 1, 5 and 10 mM 2-amino-ethylphosphonic acid, the phosphonolipid content was 23, 25, 31 and 37% of the total cellular phospholipids, respectively. This increase was accompanied by a reciprocal decrease in phosphatidylethanolamine. With 32Pi in the growth medium along with the 2-aminoethylphosphonic acid, the incorporation of the radioactivity into new molecules of 2-aminoethylphosphonic acid was almost totally inhibited, indicating a feedback control on phosphonic acid synthesis.