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were not observed for COPD or restrictive pulmonary disease among paraquat
users and nonusers who were no:nsmokers (Table 5).
Air sampling tests, in which filters from 14 people sampled at the breathing
level under normal working conditions were analyzed, showed the concentration
of paraquat to be consistently below 0.5 mg/rn3, the acceptable level
of exposure. All samples of blood and urine taken from users of paraquat in
this study gave negative results.
Discussion
Those exposed to a high level of paraquat consistently displayed a higher
prevalence of symptoms related to colds that affected the lower respiratory
tract. Subsequent medical examination showed that this symptom complex
was a good indicator of the presence of COPD. Clinically diagnosed chronic
bronchitis was the predominant disease category with a higher prevalence
among paraquat users than nonusers.
The pulmonary function tests clearly demonstrated the statistically significant
occurrence of COPD among paraquat users. The prevalence of COPD was
higher among paraquat users who smoked compared with nonsmoking users,
but the statistical significance was weak, probably because of the small sample
size.
There were no significant differences with regard to restrictive lung disease
between users and nonusers of paraquat. The largest proportion of those with
restrictive disease were among those not using paraquat; exposure to dust and
other irritants may have contributed to the condition. However, only two
paraquat users reported previous dust exposure and their pulmonary function
tests were within normal limits.
The occurrence of COPD in this occupational group was unexpected. This is
the first time such an association has been described; poisoning by paraquat
more commonly produces restrictive lung disease. It is not known to what
extent duration and levels of exposure may have influenced the study findings.
Less than 5 years has elapsed since paraquat was introduced in Carmen
de Viboral and the levels of observed exposure were within suggested limits.
Acknowledgment-This research 'was carried out with the assistance of a
grant from the International Development Research Centre, Canada.
Grant, H.C.; Lantos, EL.; Parkinson, C. 1980. Cerebral damage in paraquat poisoning.
Histopathology, 4, 185-195.
Hearn, C.E.D.; Keir, W. 1971. Nail damage in spray operators exposed to paraquat.
British Journal of Industrial Medicine, 28, 399-403.
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