Benzidine

92-87-5

Organic synthesis; manufacture of dyes.

Grayish-yellow, white or reddish gray crystalline powder.

184.23

Since benzidine has a high boiling point and a moderate aqueous
solubility, volatilization from water should not be a
significant transport process (Callahan 1979).

Benzidine exists as the neutral molecule and as a singly and
doubly ionized cation at environmental pH's. 
It is not
surprising therefore that adsorption to soil should be
sensitive to the soil pH. 
In a study of the adsorption of
benzidine to 14 soils and sediments, it was found that the
Freundlich adsorption constant was not correlated with
percentage of organic carbon, but rather with soil pH. 
The pH
contrals the amount of benzidine in teh ionized form and
sorption increases as the pH decreases, that is as a greater
fraction of the total benzidine occurs in the ionic form. 
The
adsorption of the ionized species was highly correlated with
soil surface area, while that of the neutral form was
correlated with soil organic matter. 
The Freundlich adsorption
constant for the 14 soils and sediments ranged from 50 to 3940
on a molar basis (Zierath 1980).

In a study with 4 soils the Freudlich adsorption constants
ranged from 7600 to 21 000 and the mean 1/n was 0.768. 
Even
though benzidine was largely present as the neutral species and
the sorption was correlated the organic carbon, the Koc values
are greater than can be accounted for by hydrophobic sorption
(Graveel et al. 1986).

Koc values obtained were 4899, 462 and 3307 for the three
estuarine sediments (the organic carbon contents were 0.93, 1.3
and 3.01%, respectively). 
Additionally, the distribution
coefficients were inversely related to the salinity of the
water (Johnson & Means 1986).

For adsorption to chesapeake Bay sediment, the Freundlich
adsorption constant was 6025 and 1/n was 0.75 at pH 7.9.

Adsorption increased as pH decreased, indicating that the
protonated form of benzidine was more strongly bound to
colloids than the neutral form (Means & Wijayaratne 1987).

A sequential extraction procedure was used to show that
benzidine binds to soil in two phases. 
Initially a reversible
equilibrium is established followed by covalent bonding to soil
organic matter, primarily humic acid (Graveel et al. 1986).

The benzidine concentration in soil decreases rapidly over the
first 6 hours and then more slowly. 
After 48 hr the level of
benzidine in soil solution remainsconstant, 6-22 ppb for soil
application rates of 30-50 ppm (Ononye et al. 1977).

Benzidine adsorbs to clay minerals forming a blue-colored
species, the adsorption increasing with decreasing pH (Furukawa 
& Brindley 1973).

Theoretical distribution:
> 91 % in water, the rest in sediment and soil 
(Nordic 1988).

Benzidine adsorbs light above 290 nm and is therefore a
candidate for direct photolysis. 
Its half-life when irradiated
in methanol at 254 nm is 2 hr (Lu et al. 1977).

When benzidine was adsorbed on silica gel and irradiated for 17
hr with radiation >290 nm, 40.8% degradation occurred (Freitag 
1985).

Photooxidation half-life in air:
3.12hr - 0.312hr, scientific judgement based upon estimated
rate constant for reaction with hydroxyl radical in air
(Howard 1991).

Probable reactions in air: photolysis and oxidation with ozone.

Estimated half-life approximately 1 day (Radding et al. 1975).

Benzidine (1-70 ppb) is completely removed from undisturbed,
aerated or chlorinated lake water in 24 hr. 
When aerated
solutions of benzidine (100 ppb) were exposed to a xenon lamp
(300-400 nm), it complitely degraded in 12 hr (Baird et al. 
1977).

Benzidine is very rapidly oxidized by Fe(III) and several other
natural cations which are found in environmental waters,
complexes of fulvic acid, and in clay minerals. 
Little is known
about the products of degradation (Callahan 1979).

Photooxidation half-life in water:
72.5d - 1.3d, scientific judgement based upon estimated rate
constants for reactions of representative aromatic amines with
OH and RO2. 
It is assumed that benzidine reacts twice as fast
as aniline (Howard 1991).

Benzidine was reported to be stable for 9 weeks to degradation
by soil bacteria (Yoshida et al. 1973).

In Drummer silty clay loam 79% of benzidine was lost in 4
weeks (Lu et al. 1977).

When applied to asilt loam soil (pH 5.4) and incubated for 45
days 3.3% of benzidine was mineralized. 
After 365 days
8.13-11.6% of benzidine had mineralized in 4 soils (pH
5.2-7.8). 
Amendation of the soil with glucose or alfalfa forage
had no effect on the decomposition rate. 
The low decomposition
rate compared with that in simulated treatment plants suggests
that degradation may be controlled by the soil environment or
adsorption to soil (Graveel et al. 1986).

When benzidine in sludge was applied to a sandy loam soil in a
biological soil reactor and worked into the top 20 cm of soil,
42% degraded in 48 days and 55% degraded in 97 days. 
The
overall half-life was 76 days (Kincannon & Lin 1985).

No mineralization occured when 0.05 ppm of benzidine was
incubated for 5 days with activated sludge (Freitag 1985).

Aerobic half-life:
8d - 2d, based upon aerobic soil die-away test data (Howard 
1991).

Anaerobic half-life:
32d - 8d, scientific judgement based upon estimated
unacclimated aqueous aerobic biodegradation half-life (Howard 
1991).

80 % reduction after 4 weeks incubation in soil (Lu et al. 
1977).

Degradation ways: methylation, acetylation in microbial
degradation in soil (Lu et al. 1977).

Degradation in soil - enzymes, photochemical, free radicals.

Half-life in water: approximately 100 days (Radding 1975).

Possible biooxidation products scanned by GC/MS:
N-hydroxybenzidine; 3-hydroxybenzidine;
4-amino-4'-nitrobiphenyl; N,N'-dihydroxybenzidine;
3,3'-dihydroxybenzidine; 4,4'-dinitrobiphenyl
(Verschueren 1983).

Not easily degradable
(Rudoph & Boje 1988).

Benzidinedihydrochloride is more persistent than benzidine
(Bowman et al. 1976).

Activated, aerated  active sludge promotes degradation of
benzidine (Tabak & Barth 1978).

85 - 93 % reduction of 20 mg/l benzidine after 6 hours at 20 °C
in biological aerobic wastewater treatment process (Baird et
al. 1977).

Degradation products of special interest:
Acetyle derivate of benzidine (microbial degradation,
metabolites); colouring agents based on benzidine degrade to
benzidine; with chlorination of benzidine in water forms
degradation products of chloroamine type (IARC 1982, Lu et al. 
1977, Jenkins & Baird 1975).

Fastly absorbed (USEPA 1980d).

3-hydroxybenzidine (80 - 90 %), diacetylbenzidine (5 - 10 %),
monoacetylbenzidine (1 - 5 %) and benzidine is detected in
urine (IARC 1982).

In a 42-day experiment in a flow-through tank in which
bluegills were exposed to 14C-benzidine, the log BCF was 1.6 in
the edible potion of the fish. The depuration half-life of the
14C-residues was about 7 days (USEPA 1980).

After 3 days in amodel ecosystem the log BCF for fish,
mosquitos, snail and algae were 1.74, 2.66, 2.81 and 3.4,
respectively (Lu et al. 1977).

Bioconcentration factor (crustaceans):
290, Daphnia (Lu et al. 1977).
  
Bioconcentration factor (algae):
2620, Oedogonium (Lu et al. 1977).
  
Bioconcentration factor (other organisms):
650, Physa (Lu et al. 1977).

Carcinogenicity: positive 
(McCann et al. 1975).

Colouring agents based on benzidine induces cancer in rats and
people, at the same time as benzidine is detected in urine
(IARC 1982).

Acetyle derivate of benzidine induces cancer in test animals
and are mutagen in Ames test with metabolic activation 
(IARC 1982).

Mutagenicity in the Salmonella test: positive;
1.4 revertant colonies/nmol
265 revertant colonies at 0.050 mg/plate (McCann et al. 1975).

Mutagen in Ames test when metabolic activation is present
(Fishbein 1984).

Mutagenic effects in Drosophila melanogaster (Fahmy & Fahmy 
1977).

Chromosome changes in people exposed at work
(Bassendowska-Karska 1980).

Ctenopharyngodon idella; Cyprinus carpio; Tinca tinca:
10 mg/kg, 2 days; cytogenetic effect: changes in the RNA and
DNA of the cell) (Al-Sabti 1986).