Environmental Engineering Reference
In-Depth Information
The chronic toxicity of the organotin compounds arises from their abil-
ities as endocrine disruptors leading to disorders such as imposex, intersex
and masculinization of abalone (ear shell,
Haliotis
sp.) The symptom of im-
posex (imposed sexual organ) is defined as a superimposition of the male
characteristic, such as a penis and vas deferens, in female gastropods [38,
39].
Schweinfurth and Günzel [40] reported on the mammalian toxicity and
risk evaluation for humans. Since TBT compounds can produce severe irrita-
tion of the skin and mucous membrane, their contact with the skin and eyes
as well as the inhalation of their spray mist or dust must be prevented. TBT
vapor is not considered hazardous. In repeated dose studies, lymphotoxicity
and hepatobiliary toxicity were predominant findings. There was no evidence
of damage to the central nervous system. From the available data, it is con-
cluded that TBTs do not represent a mutagenic, teratogenic or carcinogenic
hazard to humans.
3
Degradation of Organotin Compounds
3.1
Organotin Compounds as Ideal Antifoulants
Most organotin researchers' faith in organotin compounds as ideal an-
tifoulants remained unshaken till early in the 1980s; this was because much
experimental data actually showed that the above was true. In the mid 1960s,
Professor Matsuda frequently said to us in his research laboratories “Organo-
tin compounds are ideal compounds because they change to nontoxic inor-
ganic tin compounds after we have used them”.
Triorganotin compounds undergo degradation in the environment via
progressively less toxic di-(R
2
SnX
2
) and mono-organotin (RSnX
3
)deriva-
tives, to form a harmless inorganic tin residue. This cleavage of the tin-
carbon bonds may occur photolytically by UV light, microbiologically by
fungi or bacteria, or by chemical attack, and a typical breakdown scheme for
the TBT and TPT compounds is illustrated in Fig. 3 [41]. Therefore, organotin
researchers did not expect the early environmental problems caused by the
organotin compounds.
3.2
Degradation of Organotin Compounds
by Hydrolysis, Ultraviolet Light and Microorganisms
The degradation of the organotin compound may be defined as the progressive
removal of organic groups from the tin atom as shown in Eq. 2 (see Fig. 3).
