CFIA plays the 99 per cent numbers game

CFIA is getting into the 99 per cent game, usually reserved for hucksters on TV.

99.9 per cent sounds good, but that’s only a 3-log reduction. For food safety purposes, log-5 (99.999 per cent) to log-7 (99.99999 per cent) reductions in dangerous pathogens are often strived for.

Last week, the Canadian Food Inspection Agency announced that 99.8 per cent of whole cantaloupe samples tested negative for the presence of Salmonella (they didn’t test for Listeria, but should have).

cantaloupe.salmonellaPlaying the 99 per cent game is also terrible risk communication: it doesn’t matter how small the percentage of positive samples were if you were one of the 23 people that dies from Listeria in Maple Leaf cold-cuts in 2008.

Data and sampling are a necessary evil and I’m glad CFIA is making the results public. But testing is limited and fraught with caveats. It’s expensive, and industry has lots of data, so why not make it public, in the context of an overall approach to food safety for a specific food.

CFIA reports  a total of 499 whole cantaloupe samples were collected and tested for Salmonella bacteria, which can cause a serious illness with long-lasting effects. One sample was found to be unsatisfactory due to the presence of Salmonella.

A week later, CFIA said more than 99.9 per cent of leafy green vegetable samples had no detectable levels of bacterial pathogens and were safe to consume.

As part of a five-year microbiological plan that began in 2008/2009, the CFIA analyzed a total of 4,250 domestic and imported, whole and fresh-cut fresh leafy vegetable samples available in the Canadian market for Salmonella, E. coli O157:H7, E. coli O157:NM and generic E. coli. The fresh-cut samples were also tested for Listeria monocytogenes.

The 2009/2010 study deemed 12 samples to be “unsatisfactory” due to the presence of Salmonella, Listeria monocytogenes, and/or high levels of generic E. coli. None of the samples were found to be positive for E. coli O157:H7 or E. coli O157:NM.