Who Food Additives Series 59 Safety Evaluation Of ... - ipcs inchem

ACIDIFIED SODIUM CHLORITE 37
results of a wide-ranging survey measuring the chlorite levels from water samples
from across the water distribution networks were used to assess the potential
chlorite intakes of the volunteers who drank tap water. A two-way analysis of
variance (ANOVA) was carried out to identify the interactions between the type of
water consumed and the G6PD phenotype, and regression was used to compare
the blood chemistry results with the chlorite content in the drinking-water to get an
indication of the dose–response relationship. Individuals with a normal G6PD
phenotype who consumed tap water were found to have a slight but significant
change in mean corpuscular volume and mean corpuscular haemoglobin when
compared with individuals with a normal G6PD phenotype who consumed bottled
water not treated with chlorites. The authors concluded that this is probably caused
by oxidative stress due to chlorite ingestion. Individuals with a G6PD-deficient
phenotype, who in general showed a reduction in red blood cells, haemoglobin and
haematocrit and an increase in mean corpuscular volume and indirect bilirubin,
showed no further changes attributable to the type of water they consumed. The
authors therefore considered that oxidative stress caused by G6PD deficiency was
not exacerbated by the consumption of water treated with chlorites. The authors
acknowledged that the statistical power of the study was not sufficient to identify a
dose–response relationship (Contu et al., 2005).
A case–control study with incident cases was performed in nine Italian towns
between 1999 and September 2000. In total, 1194 subjects were studied, of which
343 had preterm births (26th–37th week), 239 had infants who were small for
gestational age and 612 had infants who were normal. Exposure to chlorination byproducts
was assessed by a questionnaire on the mother’s habits during pregnancy
and by water sampling directly at the mother’s home. Levels of trihalomethanes
were low (median 1.1 μg/l), whereas chlorate and chlorite levels were relatively high
(median 217 μg/l for chlorite and 77 μg/l for chlorate). The authors reported no
association of preterm babies with chlorination by-products, but noted that there
was a suggested dose–response relationship with small for gestational age.
However, the results were not statistically significant (lower confidence intervals
below 1.0), and inhalation exposure was also involved; therefore, the results of this
study cannot be considered evidence of an effect of dietary exposure to chlorite
(Aggazzotti et al., 2004).
3. DIETARY EXPOSURE
3.1 Sources other than food additives
No known natural occurrences have been identified for sodium chlorite, but
it is used commercially in substantial amounts in the production of chlorine dioxide
for various applications (e.g. bleaching textiles, disinfection and pulp and paper
processing) and is also a recognized water disinfection by-product (International
Agency for Research on Cancer, 1991).
Chlorite occurs in drinking-water at concentrations ranging from 3.2 to 7.0
mg/l when chlorine dioxide is used for disinfection purposes (World Health
Organization, 2003). Chlorine dioxide, chlorite and chlorate may occur in foodstuffs