144
P. Sahu
in agricultural product and livestock products, via food chain (Kumarathilaka et al.
2016). Various concentrations of ClO 4
− are detected in various food types such
as dairy products, beverages, meats, fruit and vegetables (Kim et al. 2014), and it
depends on various factors such as species types, age of plant, presence and concentration of other nutrients and ions in the medium and transpiration efficiency (Smith
et al. 2004).
6.5 Potential Impact of Perchlorate on Living Organisms
6.5.1 Impacts of Perchlorate Toxicity on Animal and Human
To understand the health impacts of ClO 4
− in humans, many animal toxicity studies
have been carried out. Generally, the dosage used for animal is much more than
that of potential human exposure (Keil et al. 1998). Study reveals that in presence
of ClO 4
− , treated rodents suffer from hypertrophy and hyperplasia (Caldwell et al.
1995; Lewandowski et al. 2004), and long exposures may convert some lesions to
cancerous thyroid tumours (Kessler and Kruskemper 1966; Pajer and Kalisnik 1991).
In fish, thyroid hormones partially or fully control certain biological processes such as
reproduction, ovarian maturation and oogenesis, temperature tolerance, formation of
the stomach and muscular development and highly affected in the presence of ClO 4
−
(Blanton and Specker 2007). It is proved that ClO 4
− is carcinogenic, and its high dose
application on rats for a long period causes tumour formations. As rats and human
thyroid functions in similar way, information revealed from rat toxicity studies are
considered as relevant to human also.
In case of human, after consumption of ClO 4
− through drinking water or by ClO 4
−
contaminated food, ClO 4
− is adsorbed very fast and reaches to the bloodstream
through stomach and intestines. Study of Dasgupta et al. (2006) has been reported
that ClO 4
− is present in different human body fluids such as urine, breast milk, saliva
and blood, and it is mainly due to the ingestion of ClO 4
− contaminated water and
food (Smith et al. 2006). The half-life of ClO 4
− in human serum is about 6–8 h, and
it remains unchanged during this tenure, and then, it is rapidly eliminated from the
body through urination. Various studies have described that the presence of ClO 4
− in
human body may lead to inhibition of iodine uptake as iodide into thyroid gland of
healthy adult humans (Brabant et al. 1992; Dasgupta et al. 2006). Due to same ionic
charge and almost same ionic radius of ClO 4
− ions and iodide ion, iodide uptake
by the thyroid follicle cells is hinderer by ingestion of ClO 4
− (Tietge et al. 2005).
This substitution of iodide by ClO 4
− decreases thyroid hormone production. As a
result, reduction of serum T3 and T4 and increase in TSH levels are observed in
the adult. Thyroid hormones are the main growth controlling hormone which helps
in normal growth, particularly of infants and children, as well as controlling proper
brain development and metabolic activities (Goleman and Carr 2006). This hormonal
disbalance results hyperplasia, which ultimately may lead to hypothyroidism. This
P. Sahu
in agricultural product and livestock products, via food chain (Kumarathilaka et al.
2016). Various concentrations of ClO 4
− are detected in various food types such
as dairy products, beverages, meats, fruit and vegetables (Kim et al. 2014), and it
depends on various factors such as species types, age of plant, presence and concentration of other nutrients and ions in the medium and transpiration efficiency (Smith
et al. 2004).
6.5 Potential Impact of Perchlorate on Living Organisms
6.5.1 Impacts of Perchlorate Toxicity on Animal and Human
To understand the health impacts of ClO 4
− in humans, many animal toxicity studies
have been carried out. Generally, the dosage used for animal is much more than
that of potential human exposure (Keil et al. 1998). Study reveals that in presence
of ClO 4
− , treated rodents suffer from hypertrophy and hyperplasia (Caldwell et al.
1995; Lewandowski et al. 2004), and long exposures may convert some lesions to
cancerous thyroid tumours (Kessler and Kruskemper 1966; Pajer and Kalisnik 1991).
In fish, thyroid hormones partially or fully control certain biological processes such as
reproduction, ovarian maturation and oogenesis, temperature tolerance, formation of
the stomach and muscular development and highly affected in the presence of ClO 4
−
(Blanton and Specker 2007). It is proved that ClO 4
− is carcinogenic, and its high dose
application on rats for a long period causes tumour formations. As rats and human
thyroid functions in similar way, information revealed from rat toxicity studies are
considered as relevant to human also.
In case of human, after consumption of ClO 4
− through drinking water or by ClO 4
−
contaminated food, ClO 4
− is adsorbed very fast and reaches to the bloodstream
through stomach and intestines. Study of Dasgupta et al. (2006) has been reported
that ClO 4
− is present in different human body fluids such as urine, breast milk, saliva
and blood, and it is mainly due to the ingestion of ClO 4
− contaminated water and
food (Smith et al. 2006). The half-life of ClO 4
− in human serum is about 6–8 h, and
it remains unchanged during this tenure, and then, it is rapidly eliminated from the
body through urination. Various studies have described that the presence of ClO 4
− in
human body may lead to inhibition of iodine uptake as iodide into thyroid gland of
healthy adult humans (Brabant et al. 1992; Dasgupta et al. 2006). Due to same ionic
charge and almost same ionic radius of ClO 4
− ions and iodide ion, iodide uptake
by the thyroid follicle cells is hinderer by ingestion of ClO 4
− (Tietge et al. 2005).
This substitution of iodide by ClO 4
− decreases thyroid hormone production. As a
result, reduction of serum T3 and T4 and increase in TSH levels are observed in
the adult. Thyroid hormones are the main growth controlling hormone which helps
in normal growth, particularly of infants and children, as well as controlling proper
brain development and metabolic activities (Goleman and Carr 2006). This hormonal
disbalance results hyperplasia, which ultimately may lead to hypothyroidism. This