157
-18 -16
-14 -12
-10 -8
-6 -4
-2
Pasteurized milk,
Baseline Raw milk,
Baseline Raw milk
tested cheese lot
Baseline Alternatives:
125 g vs 25g 1 cheese vs 5
cheeses Sensitivity test:
0.5 vs. 0.75
Sensitivity test: 0.9
vs. 0.75 Intra lot
contamination 0.5 vs. 2.5
Intra lot contamination
1.0 vs. 2.5 95 of the lot
tested vs 100
90 of the lot tested vs
100
Median risk per serving Mean risk per serving
Median Reference Pasteurized milk Mean Reference Pasteurized milk
Figure 24: Log
10
median ♦ and log
10
mean
■
risk per serving at random for the Elderly population, Canada, comparing pasteurized-milk soft-ripened cheese baseline, farmstead raw-milk soft-ripened cheese
with cheese lots tested and alternatives. See text for details.
11. Limitations, Caveats and Data Gaps
This quantitative risk assessment includes analysis of the available scientific information and data in the development of the exposure assessment of L. monocytogenes in soft-ripened cheese
in Canada and in the U.S. and in the development of the hazard characterization’s dose-response function in susceptible and non-susceptible populations.
The model and, as a consequence, the results and conclusions of this study are limited to the pathogen, the type of cheese and the countries Canada and U.S. considered here. Facing a lack
of available data, we did not evaluate the risk from consumption of semi-soft cheese as requested in the charge.
158 Cheese may be portioned before packaging, at the manufacturer or at retail, but this practice was
not included in this risk assessment. All conclusions refer solely to the risk of invasive listeriosis from the presence of L. monocytogenes in the considered cheese: the assessment of any
mitigation should consider, additionally, the potential impact of mitigations on other pathogens.
As in all risk assessments, results rely on inferences from limited data and on extrapolations •
over time; for example, from bulk tank surveys carried out in the 1990s to current day farm bulk tank characteristics and from nutrition surveys done in the early 2000s to
present day; •
over space; for example, from observations on bulk tank milk concentrations reported from studies in the United States, Canada and Europe;
• from samples to sampling populations; for example from data set or results sample via
the sample design to the sampling population; and, •
from a sampling population to the reference population of interest; for example, o
from U.S. retail and home storage data to Canada; o
from U.S. retail-level contamination levels and frequency to Canada; o
from all Brie and Camembert cheese consumption to raw-milk Camembert cheese consumption;
o from characteristics from women of child-bearing age to the same characteristics
of pregnant women; and, o
from laboratory to production-- from study populations to populations appropriate as a reference for this study.
Biases and uncertainty that those extrapolations introduce are unknown.
Indeed, it was not always possible to obtain some specific data for each country and for each subpopulation within each country. As a default, data obtained in one country were applied
directly to the other one, whenever needed. Table 67 summarizes the level of variability that was distinguished for each of the major parameters of the model. Because of propagation of the
variability within the model, the risk estimates are different for each subpopulation and each country. Nevertheless, only a part of the overall variability is eventually considered, due to the
