Toxicology

1. Solvents and pollution
Domina Petric, MD

2. Solvents can be devided into:
Halogenated aliphatic
hydrocarbons
Aromatic
hydrocarbons

3. Halogenated aliphatic
hydrocarbons (HAH)
carbon tetrachloride
chloroform
trichloroethylene
tetrachloroethylene (perchloroethylene)
1,1,1-trichloroethane (methyl chloroform)

4. HAH
• Perchloroethylene and
trichloroethane are still in use for dry
cleaning and solvent degreasing.
• Dry cleaning is listed as a class 2B
carcinogenic activity by the
International Agency for Research
Against Cancer.

5. HAH
• The common halogenated aliphatic
solvents also create serious
problems as persistent water
pollutants.
• They are widely found in both
groundwater and drinking water as
a result of poor disposal practices.

6. Mechanism of action, clinical effects
• These substances are
depressants of the central
nervous system in
humans.
• Chloroform is the most
potent depressant.

7. Mechanism of action, clinical effects
Chronic exposure to
tetrachloroethylene and
1,1,1-trichloroethane can
cause impaired memory
and peripheral neuropathy.

8. Mechanism of action, clinical effects
• Hepatotoxicity is also a common
toxic effect that can occur in
humans after acute or chronic
exposure.
• Carbon tetrachloride is the most
potent to cause hepatotoxicity.

9. Mechanism of action, clinical effects
Nephrotoxicity can
occur in humans
exposed to carbon
tetrachloride,
chloroform and
trichloroethylene.

10. Mechanism of action, clinical effects
There is significant
association between
exposure to the HAHs and
RENAL, PROSTATE and
TESTICULAR CANCER.

11. HAH toxicity
Neurotoxicity
Hepatotoxicity
Nephrotoxicity
Cancerogenesis

12. Treatment
There is no specific
treatment for acute
intoxication resulting from
exposure to halogenated
hydrocarbons.

13. Aromatic hydrocarbons (AH)
Benzene
Toluene
Xylene

14. Benzene
• Benzene is used for its solvent
properties and as an intermediate in
the synthesis of other chemicals.
• It is important component of gasoline.
• Permissible exposure limit (PEL)
is 1 ppm in the air and 5 ppm
limit for skin exposure.

15. Benzene
• The acute toxic effect of
benzene is depression of
the central nervous
system.
• Exposure to 7500 ppm for
30 minutes can be fatal.

16. Benzene
• Vertigo, drowsiness, headache and
nausea may occur at concentrations
ranging from 250 to 500 ppm.
• Exposure to concentrations larger
than 3000 ppm may cause euphoria,
nausea, locomotor problems and
coma.

17. Benzene
There is no
specific treatment
for the acute toxic
effect of benzene.

18. Benzene
Chronic exposure
leads to bone
marrow injury.

19. Benzene (chronic effects)
aplastic anemia
leukopenia
pancytopenia
thrombocytopenia
leukemia
lymphomas
myeloma
myelodysplastic
syndrome

20. Benzene
• Leukemia can occur following
exposures as low as 2 ppm-
years.
• The pluri-potent bone marrow
stem cells are target of benzene
and its metabolites.
• Benzene is a human carcinogen!

21. Toluene (methylbenzene)
It is a central nervous system
depressant and a skin and eye irritant.
It is also fetotoxic.
Exposure to 800 ppm can lead to
severe fatigue and ataxia.
10 000 ppm can produce rapid loss of
consciousness.

22. Xylene (dimethylbenzene)
• It is a central nervous
system depressant.
• Treshold limit values for
time weighted average is
100 ppm and for short-term
exposure is 150 ppm.