114
C. Picot et al.
Shellfish Contamination Data
To counteract the lack of data about phycotoxin levels in shellfish, samples
were harvested monthly, from June 2009 to June 2010, on beaches of Finist` ere
selected by three criteria: (i) the presence of several bivalve species, (ii) regular
shellfish harvesters and (iii) regular phycotoxin events (Picot 2010). OAs and
SPXs were analysed after methanolic extraction from samples, purification by solid
phase extraction and quantification by HPLC-MS/MS. DAs were extracted with a
water/methanol mixture (50/50; v/v) and analysed by HPLC-MS/MS (Picot et al.
2012). Contamination data are often excluded because of the limits of detection
(LOD) and quantification (LOQ) of analytical methods. The GEMS/Food–Euro
framework proposed different treatments according to the prevalence of censoreddata (WHO 1995):
– the quantity of censored data is less than or equal to 60 %, then, the censored
data are replaced by the corresponding LOD or LOQ divided by 2 (T1);
– the number of censored data is greater than 60 % and then:
• either the censored data are replaced by zero (T2a)
• or they are replaced by the corresponding LOD or LOQ (T2b).
The contamination data are described in Table 10.2. As, for OAs and DAs, the
censored data accounted for more 60 % of values, zero and LOD (or LOQ) values
were used in two separate estimations of the distributions and calculations (mean,
median, percentiles : : : ). On the other hand, as the censored values for SPXs were
less than 60 %, they were replaced by the half of the corresponding LOD or LOQ.
Exposure Modelling
General Exposure Model
An acute exposure corresponds to a short exposure to a harmful compound at high
dose. Let us consider a phycotoxin denoted by m. The acute phycotoxin exposure
is the amount of m ingested in a single meal. It is obtained by multiplying the
edible portion size of one shellfish species by the concentration of m in this portion.
For each phycotoxin, acute intakes were calculated individually for each shellfish
species.
Chronic exposure is a repeated exposure to low, or very low, doses for a long
time. The chronic phycotoxin exposure is the amount of m ingested daily from the
daily consumption of all shellfish species. The general exposure model used, here,
to assess individual phycotoxin intake from shellfish consumption can be expressed
as follows:
E m D
P
C mj C R j P j
BW
(10.1)
C. Picot et al.
Shellfish Contamination Data
To counteract the lack of data about phycotoxin levels in shellfish, samples
were harvested monthly, from June 2009 to June 2010, on beaches of Finist` ere
selected by three criteria: (i) the presence of several bivalve species, (ii) regular
shellfish harvesters and (iii) regular phycotoxin events (Picot 2010). OAs and
SPXs were analysed after methanolic extraction from samples, purification by solid
phase extraction and quantification by HPLC-MS/MS. DAs were extracted with a
water/methanol mixture (50/50; v/v) and analysed by HPLC-MS/MS (Picot et al.
2012). Contamination data are often excluded because of the limits of detection
(LOD) and quantification (LOQ) of analytical methods. The GEMS/Food–Euro
framework proposed different treatments according to the prevalence of censoreddata (WHO 1995):
– the quantity of censored data is less than or equal to 60 %, then, the censored
data are replaced by the corresponding LOD or LOQ divided by 2 (T1);
– the number of censored data is greater than 60 % and then:
• either the censored data are replaced by zero (T2a)
• or they are replaced by the corresponding LOD or LOQ (T2b).
The contamination data are described in Table 10.2. As, for OAs and DAs, the
censored data accounted for more 60 % of values, zero and LOD (or LOQ) values
were used in two separate estimations of the distributions and calculations (mean,
median, percentiles : : : ). On the other hand, as the censored values for SPXs were
less than 60 %, they were replaced by the half of the corresponding LOD or LOQ.
Exposure Modelling
General Exposure Model
An acute exposure corresponds to a short exposure to a harmful compound at high
dose. Let us consider a phycotoxin denoted by m. The acute phycotoxin exposure
is the amount of m ingested in a single meal. It is obtained by multiplying the
edible portion size of one shellfish species by the concentration of m in this portion.
For each phycotoxin, acute intakes were calculated individually for each shellfish
species.
Chronic exposure is a repeated exposure to low, or very low, doses for a long
time. The chronic phycotoxin exposure is the amount of m ingested daily from the
daily consumption of all shellfish species. The general exposure model used, here,
to assess individual phycotoxin intake from shellfish consumption can be expressed
as follows:
E m D
P
C mj C R j P j
BW
(10.1)