Dusts were collected in citrus orchards and in vineyards from leaf sur
faces in the area where harvest operations were ongoing. Six milligram
s of each of the dusts was instilled intratracheally into the lungs of
rats. All dusts contained approximately the same amounts of quartz. T
hree days later, the lung lavage fluid was assayed for protein and cel
l content. In animals that had been exposed to vineyard dusts, the per
centage of polymorphonuclear leukocytes in the recovered cells was sig
nificantly higher than in control animals. This change was not seen in
animals exposed to citrus orchard dusts. One of the vineyard and one
of the citrus orchard dusts were instilled either once or four times i
nto other animals, and lung hydroxyproline content, lung lavage compos
ition, and incorporation of bromodeoxyuridine into cellular DNA was me
asure 1 wk later. Following a single instillation, vineyard dust produ
ced signs of increased cell proliferation in the large airways and ter
minal bronchioles and, after four installations, was associated with a
n increase in total lung hydroxyproline. Citrus orchard dust showed no
such effects. These data suggest that dusts generated during grape ha
rvesting operations have fibrogenic potential, and that this might exp
lain the presence of signs of restrictive lung disease ascertained in
epidemiological studies in vineyard workers.