Having full time RVed for 8 plus years, it shocked me when I saw a fellow RVer dumping their holding tanks without using rubber gloves or taking any precautions to insure the process of dumping would be sanitary.  The fact is, there are 2 factors that can affect your health. 

1. The health effects of sewer gases
2. The fecal contaminants around the RV site before during and after the dumping process

SEWER GASSES
Rule of thumb, “If it can explode, it should not be breathed."

These gases are sometimes present during the dumping of holding tanks coming from your own black holding tank or from the sewer system in the park. Sewer gas is a generic name for a complex mixture if gases and airborne agents that result from the natural process of the decomposition of organic materials in sewage. Most common gases include hydrogen sulfide (H2S), ammonia (NH3), methane (CH4), and carbon dioxide (CO2). Sewer gas also contains carbon dioxide (CO2), nitrous oxides (NOx), biological organisms and water vapor. The major adverse health effects from exposure to sewer gasses include 1. Poisoning from hydrogen sulfide gas; 2. Fatigue do to reduced oxygen levels (from CO2 and CH4); 3. Diseases from airborne pathogens, bacteria, viruses etc; 4. Explosions from methane gas.   And all this from something you do not physically come in contact with. 

FECAL CONTAMINANTS

The direct contact with Human faecal waste contains pathogens (disease carrying bacteria, viruses, protozoa (single cell organisms), parasites and some fungi which can cause disease in humans. This disease spread can by direct contact, ingestion or inhalation. 

THE DANGERS

If you look at the water bay in most RVs you will see the fresh water inlet very close to the sewer cap outlet. Think about the vapor gases coming from the sewer outlet when you remove the cap. Where does the vapor and gas go besides up your nose? This has the potential to cause minor and major health problems over time. Some RVers use the same rubber gloves over and over. They might as well use their bare hands because they store the soiled gloves in the same compartment as the fresh water inlet. RV manufacturers could design a system where you would never come in contact with the waste and isolate the waste from gas contact with the fresh water input.  

The benefit to a system like this goes beyond the individual health aspects (which are very important) it also helps the EPA attain it's Safe Drinking Water Act (SDWA) which ensures we have safe drinking water in the future. How many times have you found a mess left by others at your site? This ground water contamination can be stopped if a system was included with the RV to prevent spills and the necessity to clean the hose and fittings before storage.