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I don't generally wash salad unless it looks dirty. It's not that I'm unaware of E-coli and pesticides etc, it's that I don't have any conviction that rinsing them with water will significantly remove such nasty contaminants.

Am I wrong? Is there any hard evidence to support the idea that rinsing salad, without soap or scrubbing, will really render it safe?

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    While these aren't strictly duplicate questions, I think the answers on them address this question, so I wonder if we can close it as a duplicate anyway. Does washing vegetables remove nutrients?, Do fruit/vegetable washes effectively remove pesticides?.
    – Oddthinking ♦
    Commented Jul 21, 2016 at 9:09
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    Either for notable claim or answer: bbc.com/news/health-36823404
    – DavePhD
    Commented Jul 21, 2016 at 13:57
  • Please clarify what "salad" means, i.e.: those vegetable/fruit/fungi ingredients of a salad in-the-making, or a bagged salad mix, or what? By the usage of the noun "salad" I'm most familiar with, it's not a "salad" until it's made, (i.e. dressed, tossed, garnished, etc.), just as soup ingredients are not soup until they are correctly prepared, combined, and cooked.
    – agc
    Commented Jul 26, 2016 at 14:03
  • I mean the raw ingredients -- spinach, carrots, etc. Dressings and arrangements aren't relevant in this context.
    – spraff
    Commented Jul 27, 2016 at 14:53

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Indeed you're wrong.

A study reported that washing lettuce leaves with tap water for 15 s provided a log reduction of 1.16 (93.08 %) of the E. coli population, while "prolonging washing time with running tap water to 30 s significantly increased (P < 0.05) this reduction to 2.2 log CFU per leaf" — that is, 99.37 %.

The study also mentions better results on cabbage, lemons and tomatoes (though while "thoroughly rubbing" them), and reports that a log reduction of 5.68 (99.9998 %) is achieved after rubbing tomatoes for only 8 s under tap water.

Reference : Reduction of Escherichia coli O157:H7 on Produce by Use of Electrolyzed Water under Simulated Food Service Operation Conditions (open access PDF), Pangloli et al, Journal of Food Protection, 72, 9, 2009. (Note that it uses tap water as control, the purpose of the paper being electrolyzed water.)

NB : You asked about Escherichia coli specifically, but there are similar reports about other pathogens, e.g. another study found that simply rinsing (without rubbing) broccoli/lettuce leaves, apples and tomatoes for 15 s resulted in a removal of Listeria innocua (used as a surrogate for Listeria monocytogenes) by 96.11 %, 99.02 % and 99.21 %, respectively (log reduction of 1.41, 2.01 and 2.10).

Reference : Efficacy of Home Washing Methods in Controlling Surface Microbial Contamination on Fresh Produce (open access PDF), Agnes Kilonzo-Nthenge, Fur-Chi Chen, Sandria Godwin, Journal of Food Protection, 69, 2, 2006.

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