Tuesday, May 30, 2006


Hi everyone!

Hey - just in case you missed...Open Heart Farm has been featured in the past two weeks' worth of Seven Days!

My last blog post was published by columnist extraordinaire Cathy Resmer in the May 24-31st issue (page 8A)

And Open Heart was featured in the Intervale Explorer, compiled by Sarah Jelen


We want to mention some of the latest drama going on down at the Intervale this week - we were visited by a representative of the health department last week, at the request of some of the farmers actually, who gave us some statements (not backed by any data, actually, and that was frustrating!) re: lettuce post-flood - As many of the farmers make a nice chunk of change this time of year on their yummy organic brimming-with-goodness head lettuce right about now, they were very concerned that folks would be put off by some of their crops (and ours too!) having been submerged by the Winooski, and the health dept. rep confirmed and fueled worries - He had no data or evidence really to back up his recommendation that lettuces be tilled under, but that was his recommendation

THEN, One of the Intervale farmers did quite a bit of research on the matter and I will post it below...however...IN SUM...the data we've been able to find states that none of the bacteria that would be inhabiting any lettuces would be able to survive outside of their watery home for more that a day or so - obviously we've already outlived them many times over at this point (since 2 weeks ago, when the flood receded)

BUT - this is of course up to each consumer of said lettuce - and Josh and I are happy to converse with anyone of course about specific crops/fields

ALSO, just so you know, farmers are still selling lettuce hand over foot to local markets, who are all in the know about the flood, and of course farmers and their families are all eating it

we just thought we should detail some of this information that's been floating around us - we're eating our lettuce, and in any case, that's the only thing at OH Farm that is at all in question -

so, without further ado, here's that scientific stuff to add to the conversation:

"The most common waterborne disease-causing agents and their half-life residence times outside the human intestine.
Salmonella 2.4-19.2 hours
E. Coli/Shigella 22.4-26.8 hours second most common disease- causing bacteria in U.S.
Giardia lamblia 4 days at 37 degrees C

These data taken from Environmental Microbiology by Maier, Pepper and Gerba
c. 2000 show that far from the proposal that the enteric bacteria would continue to grow as the plants grow, the organisms would actually decline rapidly in number. These organisms are adapted to thrive within the human intestinal tract and are stressed severely outside of that dark, anaerobic environment.
The fecal coliform test would be the most common method to test for these enteric pathogens and would be an adequate indicator for prevalence of the Salmonella and the E. coli bacteria. The Giardia parasite is less correlated with the fecal coliform test. No fecal coliform test was indicated at the emergency meeting today, but we can assume it may have exceeded the federal guidelines of under 200 colony forming units (CFU) per 100 ml as a summer discharge regulation for sewage waters. The limit for water for irrigation of agricultural crops is 100 CFU/100 ml. It is difficult to determine how the coliform levels would be affected by the flooding, since on one hand there is likely to be increased runoff and possible sewage treatment bypass, and on the other hand the increased water volume enhances the dilution factor. In lieu of concrete data, let us assume a magnitude jump in coliform levels to 2000 CFU/100ml on the day of the flood. The most common bacteria will be the Salmonella and the Shigella strains since they make up the highest proportion of human feces (again from Environmental Microbiology). Since these bacteria have half lives of about 20 - 26 hours on the conservative side, we can figure that by Friday, 6 days later, they have gone through 7-5.5 half lives. Conservatively this means that the original 2000 per 100 ml will have reduced to 62.5 per 100 ml. This number even is a high assumption since the water has dissipated and now the bacteria would be dry and exposed to increased oxygen levels, which is inhibitive to their growth. This number loses some relevance since the moisture levels on the plant are no longer measurable in 100ml levels. However, let us assume even that 200 CFUs remain on the plant even after 6 days of dryness. Using the microbial risk assessment criteria from the article Modeling the risk from Giardia and viruses from drinking water in the Journal of American Water Works as cited in the Environmental Microbiology book we can determine the probability of a lettuce eater being contaminated by the lettuce head. Let's assume that after thoroughly washing our lettuce head, it still contains the 200 CFUs of E. coli that contaminated it. Using the beta-Poisson model for probability of infection as follows, P = 1 - (1+N/b) to the power of -a, and using the data for E. coli where a =0.1705 and b = 1.61 x10 6, if N = 200 per lettuce then we get a probability of infection of 0.00003, or about 1 in 30,000. Since the health department appears to use studies from the Federal Ag. Dept. who in turn use California based numbers, this number makes some sense in the scale of California lettuce production. No Vermont-based studies were cited at the meeting today. For perspective the chance of being exposed to aflatoxin (a toxin from rotting peanuts) from eating peanut butter is calculated at 6 in 10,000 or about 20 times greater than our lettuce example."


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