660
Pure Mg is known to have a fast degradation in high chloride physiological environment but it may produce hydrogen gas at a high rate from corrosion , which can not be dealt with by the host tissue .
 material: Pure Mg; concept or principle: degradation; concept or principle: gas; concept or principle: corrosion; material: be
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 material: Pure Mg; concept or principle: degradation; concept or principle: gas; concept or principle: corrosion; material: be