Black Diamond tested the breaking point of wet and dry runners. We're generally supportive of the abuse of runners - what kind of sport is that, really? - yet initially we were sketical; surely a wet person will break at the same point as a dry person. Then we realized they were talking about webbing! Nylon and Dynex specifically:
"Dynex runners don’t seem to be affected when soaked, which was to be expected. Nylon runners, on the other hand, show about a 10% decrease in strength when wet. Should this slight decrease in strength be concerning? Not really. The strength of these, wet or dry, are well above the product rating and pretty much any force that can be created in the field. Bottom line: runners are crazy strong, wet or dry. So even if my partner had gone for a ride during our rain-drenched climb, he would have been fine.
"Note: If your runners or other gear gets soaked, don’t dry it out in direct sunlight. This causes degradation and a potential decrease in strength. How much? Check out an entry from the QC Lab archives: Testing Old Gear from the VRG. Dried out and sun-bleached slings broke at around 11 kN with some as low as 5 kN. That’s 1124 lbf and getting well into sketchy land."