3 results and discussion 31 assessment of total

3. Results and discussion
3.1. Assessment of total arsenic and its speciation in raw rice
3.1.1. Total arsenic
As
t
concentrations in the samples analyzed in this study showed a large variation, spanning
between 0.041 mg kg
-1
for long-grain white organic Basmati rice from India up to 0.535 mg
kg -1 for a duo of long-grain organic rice from France (Table 4). The lowest levels were found
in Basmati rice, ranging from 0.041 to 0.129 mg kg
-1
. Lower but still consistent levels were
found in a three-rice mix (unknown origin) (0.301 mg kg
-1
), a short-grain rice for risotto from
France (0.280 mg kg -1 ), a whole-grain rice (steamed, parboiled or steamed black rice, 0.215
mg kg -1 ) and a steamed wholegrain long-grain rice from Uruguay (0.234 mg kg -1 ). These data
are consistent with the levels reported for French rice from the ‘ Camargue ’ region (0.280 mg
kg
-1
) (Meharg et al., 2009) and with those obtained in previous studies (Pasias et al., 2013).
For instance, in a Canadian study (2009-2010) [Agence C anadienne d’ Inspection des
Aliments (ACIA), 2012] the mean level of total As (0.241 mg kg
-1
) in brown rice (range,
0.050 to 0.386 mg kg
-1
) was higher than that in white rice (mean, 0.136 mg kg
-1
; range; 0.040
to 0.190 mg kg -1 ). Likewise, a study carried out by the US Food and Drug Administration
(FDA) in 2013 on 1300 samples of rice and rice products found that As
t
was at the low end of
the range in instant rice, and at the high end in brown rice (U.S. Food and Drug

15
Administration, 2013). Since it appeared that As
t
was substantially removed from brown rice
during the industrial polishing process, the higher As concentrations in brown rice suggest
that the contaminant is attached to the bran or the surface of the rice grain (Torres-Escribano
et al., 2008; Narukawa et al., 2012; Zavala et al., 2008).
3.1.2. Arsenic speciation analysis
In all of the samples analyzed in this study, the predominant arsenic species were As
i
and
DMA (Figure 2). Because of their difference in toxicity, the results will be discussed
separately for As
i
and organic arsenic species (represented here by DMA).
3.1.2.1. Inorganic arsenic species
For the batch of samples analyzed in this study, large variations in As
i
concentrations were
observed (Figure 3). The lowest levels were found in Indian white long-grain organic Basmati
rice (0.025 mg kg
-1
) whereas the maximum concentration (0.471 mg kg
-1
) was measured in
organic long-grain rice duo from France (see Table 4). For the other rice samples, As
i
concentration ranged between 0.080 and 0.160 mg kg
-1
in white long-grain rice (n = 5) and
from 0.099 to 0.173 mg kg
-1
in Thai white long-grain rice (organic or conventional, n = 6),
levels which are compatible with those reported elsewhere (Pasias et al., 2013; Torres-
Escribano et al., 2008).
It is also interesting to note that As
i
level was highly correlated to As
t
concentration (Figure
4). In our study, As
i
fraction (compared to As
t
) varied between 50% (three-rice mix) up to
approximately 100% in a risotto rice, which is comparable with another study (Chen et al.,
2016).