Currently, I'm scouring the FDA website for things that may or may not be safe to eat, including the EPA (regarding tap water and pesticides) and the USDA (for traditional meats and poultry). I'm going to place them under the #grasfed tag (Generally Recognized as Safe).
Any and all sources are most likely going to come from their respective websites, so I'll include the #sources tag, but if you have any concerns you should probably do your own research.
Benzene, a carcinogen, has reportedly been found in small amounts in soda. The FDA states that in sodas where both ascorbic acid and benzoate preservatives were present, benzene formation could occur. Nevertheless, studies by the FDA in 1993 and by other private laboratories reported concentrations in most sodas of less than 5ppb, the EPA maximum contaminant level (MCL), and represent little to no threat.
MSG is GRAS; however, FDA reports that a study by the Federation of American Societies for Experimental Biology (FASEB) in the 1990s identified some "short-term, transient, and generally mild symptoms such as headache, numbness, flushing, tingling, palpitations, and drowsiness in some sensitive individuals who consume 3g or more of MSG without food." It is unlikely to consume that much in one sitting without food, so take it with a grain of salt (heh). Interesting fact, MSG also occurs naturally in tomatoes!
San Diego's water quality reports from 2010 to 2012 have indicated that tap water is pretty safe to drink, meeting state and federal standards.
The EPA sets limits on pesticide residue on food, and they are generally well within tolerance by the time they reach the grocery store. We have a national pesticide information center in Oregon, and they have some tips for further reducing pesticide residue, as well as dirt and bacteria, from produce if you decide you need that extra peace of mind: http://npic.orst.edu/health/foodprac.html
A tangent, but apparently from the FSIS...
"SODIUM ERYTHORBATE - is the sodium salt of erythorbic acid, a highly refined food-grade chemical closely related to vitamin C, synthesized from sugar, and used as a color fixative in preparing cured meats. (Note: Erythorbate is NOT earthworms. Perhaps the spelling or pronunciation has contributed to this misconception because the Hotline receives many calls related to this concern.)"
From a list of commonly added food additives: http://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/food-labeling/additives-in-meat-and-poultry-products/additives-in-meat-and-poultry-products
Ralphs down here in San Diego is the same as Food 4 Less. They are also a COOL licensee, meaning they label where their meat comes from (if it's packaged), and the USDA FSIS, APHIS, FDA, and CBP all work to ensure imported meat meets the same standards at that in the US. 99 Ranch is also a COOL licensee.
Here are some terms to be aware of, courtesy of the USDA:
Certified: the USDA FSIS and AMS have officially evaluated it for class, grade, or other quality
Chemical free: not allowed to be used as a label
Free range: producers must demonstrate that the poultry has been allowed access to the outside
Natural: a product containing no artificial ingredients or added color and is only minimally processed; does not mean raw single ingredient meat or poultry!
No hormones: not allowed to be used in hogs or poultry, so pork and poultry are always hormone free; may be used on beef if producers demonstrate no hormones have been used in raising the animals
No antibiotics: may be used for meat and poultry if producers demonstrate animals were raised without antibiotics
Organic: "100% organic" for... 100% organic; "organic" contains at least 95% organic ingredients; look for the seal (none of this counts added water or salt)
It should be noted that the USDA makes no claims that organic food is healthier for you (and in some cases, might even be worse owing to a lack of preservatives). Nevertheless, organic practices help promote sustainability, which is a plus if you're into that kind of thing.