The
Cross-Sectional Studies
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In a cross-sectional study signs of the disease is sought in individuals
exposed for the suspected causal factor and in non-exposed individuals of the
same age and sex. If the
factor is causal, the disease should be seen more often in the exposed than in
the unexposed individuals.
A large number of cross-sectional studies of workers with occupational
exposure to hydrocarbons have been published. These studies included refinery
workers, dry-cleaners, floor layers ,
printers, road workers, paint sprayers and
a variety of other workers exposed to organic solvents
or fuels.
In at least fourteen studies these workers had more often urinary
findings typical for early glomerulonephritis than had the unexposed control
individuals (Askergren
et al 1981a, Askergren et al 1981b, Viau et al
1987, Hotz et al 1989, Hotz et al
1990a, Hotz et al 1990b, Hashimoto et al 1991,
Hotz et al 1991, Mutti et al
1992, Yaqoob et al 1993a, Hotz et al
1993, Stevenson et al 1995, Huber et al
1998, Pai et al 1998). In three of the studies the workers
even had a decreased renal
function more often (Hotz
et al 1990b, Yaqoob et al 1993a, Pai et al
1998).
Thus,
without doubt, exposure to hydrocarbons does induce renal damage typical of
glomerulonephritis. It should be stressed, however, that it was seen only in a few of the
exposed workers, and that these workers were healthy by all standards and had no other symptoms or signs of disease. The blood and
urinary findings were mild in most workers and may have remained undetected if
the laboratory tests had not been performed. What these studies have shown is
that hydrocarbon exposure affects the kidneys of a few individuals but to a
small degree only.
As
hydrocarbon exposure is prevalent in most societies and as clinically
significant glomerulonephritis is
a rare disease, a further factor, probably a hereditary
predisposition, is necessary. If this unknown factor is present, however, hydrocarbon
exposure may result in serious glomerulonephritis. This has been shown most
convincingly by the case-control studies.