PRINCIPLES OF TOXICOLOGY

temperatures as high as (almost) 41.8 °C (107.4 °F) have been reported. Severe overexposure to
pentachlorophenol can cause signs and symptoms such as delirium, flushing, pyrexia, diaphoresis,
tachypnea, abdominal pain, nausea, and tachycardia.
Because pentachlorophenol volatilizes from treated wood and fabric, excessively treated indoor
surfaces can lead to irritation of the skin, eyes, and upper respiratory tract. Contact dermatitis has been
reported in workers exposed dermally to pentachlorophenol. Treatment of pentachlorophenol poisoning
consists mainly of decontamination of clothing and skin and/or gastrointestinal tract as well as
supportive treatment for symptoms associated with the exposure (e.g., temperature control).
Pentachlorophenol can be assayed for in blood, urine, and adipose tissue. The ACGIH biological
exposure index for pentachlorophenol is 2 mg/g creatinine total pentachlorophenol in urine prior to
the last shift of the workweek or 5 mg/L free pentachlorophenol in plasma at the end of the workshift.
Dithiocarbamates/Thiocarbamates
The dithiocarbamates and the thiocarbamates are used as fungicidal compounds and have little
insecticidal toxicity, unlike the N-methyl carbamates (e.g., the acetylcholinesterase-inhibiting carbamate,
carbaryl) discussed earlier. Examples of thiocarbamate fungicides include thiram (AAtack),
metam-sodium (Vapam), ziram (Ziram 76), ferbam, and the ethylene bis dithiocarbamate (EBDC)
compounds—maneb, zineb, and mancozeb.
In general, the thiocarbamate class of fungicides has low acute toxicity. Thiram dust has been
reported to cause eye, skin, and mucous membrane irritation, with contact dermatitis and sensitization
reportedly occurring in a few workers. Systemic intoxications that have been associated with exposure
to thiram have resulted in symptomatology similar to that cause by reactions to disulfiram (Antabuse),
a dithiocarbamate medication used to treat alcoholism. Thiram, like disulfiram, is not a cholinesterase
inhibitor, but does cause inhibition of the enzyme acetaldehyde dehydrogenase (responsible for the
conversion of acetaldehyde to acetic acid), and reportedly, in rare cases, workers who have been
exposed to thiram have complained of “Antabuse” reactions after ingestion of alcoholic beverages.
Exposure to ziram, ferbam, and the EBDC compounds have been associated with skin, eye, and
respiratory tract irritation in humans. Maneb and zineb have been associated with cases of chronic
dermatological disease, possibly due to dermal sensitization to these compounds in workers.
Chlorothalonil
Chlorothalonil (Bravo, Daconil) (2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile) has been reported to
cause dermal and mucous membrane irritant effects in humans exposed to this compound. Chlorothalonil
appears to have low potential for toxicity in humans.
Cl
Cl Cl
Cl
Cl
OH
Figure 15.7 Pentachlorophenol.
15.5 FUNGICIDES 359