Pesticides and Skin Diseases in Man - Pesticides: Evaluation of Environmental Pollution - page 535

of the nail bed, transverse bands, or discolorations, eventually leading to the loss of the
nails (Botella et al. 1985).
16.5.13 Hair Disorders
Hair loss is a systemic symptom provoked by a range of external factors, including
acute and chronic intoxications, chemotherapy, and infections. Therefore, the negligible
number of reports on diseases of the hair induced by pesticides seems somewhat sur-
prising ( Table 16.1 ). It could be due to the actual lack of the influence of pesticides on
hair physiology, or perhaps due to the lack of interest by affected workers and occupa-
tional physicians.
16.5.14 Nonmelanoma Skin Cancer
This group includes squamous cell carcinoma (SCC), basal cell carcinoma (BCC), and
Bowen's disease, which is considered carcinoma in situ. Seven out of eight studies analyzed
by Blair and Zahm demonstrated high incidence of nonmelanoma skin cancers in farmers,
which, in the first place, was attributed to sunlight exposure but also to other environ-
mental factors (Blair and Zahm 1991). There is a strong evidence for carcinogenic effects
of arsenic pesticides. Arsenic is a metal with a clear predilection for the skin (Lansdown
1995). Until 1960s, arsenic salts were widely used as insecticides. At that time, acute poi-
sonings were very common, which suggests high exposure in many pesticide sprayers.
Arsenic compounds were first introduced and widely used in vineyards, therefore the
first reported cases of arsenic-related cancer were vintners (Roth 1956; Braun 1958; Thiers
et al. 1967). A more recent report of skin cancer related to long-term arsenic exposure was
published in 1987 (Jampel and Jerdan 1987). In an epidemiological study conducted in
Costa Rica, skin cancers (lip, melanoma, nonmelanocytic skin, and penile cancer) occurred
increasingly in coffee-growing areas with extensive use of paraquat and lead arsenate
(Wesseling et al. 1999).
The effect of arsenic compounds on the skin may become apparent many years after
the exposure. First case reports of palmoplantar keratosis appeared 10-15 years after the
introduction of arsenic into agriculture (Roth 1957). However, arsenic-related skin cancers
may emerge more than five decades after the exposure (Spiewak 2001). Therefore, every
farmer presenting with skin cancer to a doctor should be questioned for possible contacts
with arsenic compounds and other potentially carcinogenic pesticides. Typical signs of
long-term arsenic exposure are palmoplantar keratosis (excessive thickening of the hand
palms and foot soles) and chronic skin inflammation of distal body parts (acrodermatitis
atrophicans). Later in the course of the disease, Bowen's disease (carcinoma in situ), mul-
tiple BCC, and SCC with ulceration may appear (Braun 1958; Jackson and Grainge 1975).
Occupational skin cancer should be in first range considered in workers with multiple or
recurrent skin cancers, who were in the past involved in the production or spraying of
arsenic insecticides. Such patients must be checked for other epithelial tumors, especially
lung cancer.
Exposures to nonarsenical insecticides may also pose a risk for skin and lip cancer (IARC
1991). In a study of 20 workers manufacturing paraquat from 4,4′-bipyridyl, six were diag-
nosed with SCC (Bowra et al. 1982). In a large study of 228 workers exposed to bipyridyl at
21 paraquat-producing factories, two were diagnosed with Bowen's disease. Exposure to
sunlight appeared to be an important cofactor for the development of this disease (Wang
et al. 1987).