Most of the commercial versions of iodophor recommend a very small amount of the product to a large amount of water. So, i want to know if they do this because is dangerous to ingest / handle large amounts of iodophor or if they do this because efficiency (like if you use more you wont sanitize more so would be a waste). What are the overall risks involved using the product? Tks!
Iodophor's active ingredient is iodine, which is toxic to humans in sufficient doses. The recommended dilutions of iodophor are sufficient to sanitize surfaces and assume that all but a trace of the iodophor will be removed and not ingested. A larger concentration of iodine would not be more effective and so would be wasteful, and also could begin to be dangerous if enough iodine is left behind.
When used as directed, iodophor is very safe. It is used extensively in the commercial dairy industry. While iodine is toxic in large doses, it is also an essential nutrient in very small doses. For this reason, iodophor is a "no-rinse" sanitizer -- if a ml or two of diluted iodophor are left in a carboy after it is drained, its further dilution in the beer filling the container will not have any ill effect.
This is one of those things where more is not better. If you overdose your iodophor, it can lead to tasting iodine in your beer, and adding that iodine flavor to your plastic hoses and buckets. We had a commercial brewer do a test batch before the brewery opened and brought it to a party, he over did it with the iodophor and it was noticeable in the beer, several of us told him to use as directed. I think he was embarrassed but appreciative too.