Since we are talking about relative risks, here are some MSDS data summarized from the JT Baker Chemical Company. Obviously, anthing that will etch copper has got to have some risks to it. I have included the label categories of risk severity. Notice the similarities. The etchants using hydrogen peroxide and HCl or sulfuric acid can be made using use 3% peroxide; althouh, many of the recipes use 30% .
Hope this helps keep the risks in perspective. John
SEQUENCE: Health; Flammability; Reactivity; Contact
(Source:JTBaker Chemical Company MSDS)
Hydrogen peroxide 30% ---- 3,0,3,4
Hydrogen peroxide 3% ----- 2,0,1,2
Sodium persulfate ----------- 2,0,3,3
Ammonium persulfate -------2,0,3,3
Ferric chloride ---------------3,0,2,3
Hydrochloric acid 33-40% ---3,0,2,4
Sulfuric acid 52-100% --------4,0,2,4
FULL LABEL INFORMATION
AMMONIUM PERSULFATE
Health Rating: 2 - Moderate (Life)
Flammability Rating: 0 - None
Reactivity Rating: 3 - Severe (Oxidizer)
Contact Rating: 3 - Severe (Life)
SODIUM PERSULFATE
Health Rating: 2 - Moderate
Flammability Rating: 0 - None
Reactivity Rating: 3 - Severe (Oxidizer)
Contact Rating: 3 - Severe (Corrosive)
HYDROGEN PEROXIDE 30%
Health Rating: 3 - Severe (Life)
Flammability Rating: 0 - None
Reactivity Rating: 3 - Severe (Oxidizer)
Contact Rating: 4 - Extreme (Corrosive)
HYDROGEN PEROXIDE 3%
Health Rating: 2 - Moderate
Flammability Rating: 0 - None
Reactivity Rating: 1 - Slight
Contact Rating: 2 - Moderate
FERRIC CHLORIDE
Health Rating: 3 - Severe (Life)
Flammability Rating: 0 - None
Reactivity Rating: 2 - Moderate
Contact Rating: 3 - Severe (Corrosive)