## 4 Results  
### Health Hazard  
Table 3 shows the health hazard rating from both the NFPA 704 standard and GHS statements of the materials under study. As explained above, the NFPA 704 standard rates the relationship between hazard and exposure, while the GHS specifies the damages that the material can cause. \begin{table}
\begin{tabular}{c c c} \hline
**Material** & **NFPA 704** & **GHS Statement** \\ \hline HDPE & 0 & This material is not hazardous \\ \hline \multirow{3}{*}{Sebacic acid} & \multirow{3}{*}{1} & Causes skin irritation \\  & & Causes serious eye irritation \\  & & May cause respiratory irritation \\ \hline Dimethyl terephthalate & 1 & May cause an allergic skin reaction \\ \hline \multirow{3}{*}{D-manitol} & \multirow{3}{*}{1} & Hazardous in case of ingestion. Slightly hazardous in case of skin contact \\  & & (irritant), of eye contact (irritant) or inhalation \\ \hline Adipic acid & 1 & Causes serious eye irritation \\ \hline \multirow{3}{*}{Benzanilide} & \multirow{3}{*}{1} & Harmful if swallowed \\  & & May cause respiratory irritation \\  & & Causes skin irritation \\  & & Causes serious eye irritation \\ \hline \multirow{3}{*}{Dulicitol} & \multirow{3}{*}{1} & Hazardous in case of ingestion. Slightly hazardous in case of skin contact \\  & & (irritant), of eye contact (irritant), of inhalation * \\ \hline \multirow{3}{*}{Benzoic acid} & \multirow{3}{*}{2} & Harmful if swallowed \\  & & May cause respiratory irritation \\  & & Causes skin irritation \\  & & Causes damage to organs through proposed or repeated exposure \\  & & Causes serious eye damage \\ \hline \multirow{3}{*}{Benzamide} & \multirow{3}{*}{2} & Harmful if swallowed \\  & & & Suspected of causing genetic defects \\ \hline \multirow{3}{*}{Urea} & \multirow{3}{*}{2} & May cause respiratory irritation \\  & & & Causes skin irritation \\  & & & Suspected of causing cancer \\  & & & May cause damage to organs \\  & & Causes serious eye irritation \\ \hline \multirow{3}{*}{Salycilic acid} & \multirow{3}{*}{2} & Toxic if swallowed \\  & & & Causes serious eye irritation \\ \hline \multirow{3}{*}{Hydroquinone} & \multirow{3}{*}{2} & Harmful if swallowed \\  & & & Harmful in contact with skin \\  & & & Suspected of causing generic defects \\  & & & Causes serious eye damage \\  & & & May cause an allergic skin reaction \\ \hline \multirow{3}{*}{Phhalic anhydride} & \multirow{3}{*}{3} & Harmful if swallowed \\  & & & May cause respiratory irritation \\  & & & Causes skin irritation \\  & & & Causes serious eye damage \\  & & & May cause allergy or asthma symptoms or breathing difficulties if inhaled \\ \hline \multirow{3}{*}{Maleic acid} & \multirow{3}{*}{3} & Harmful if swallowed \\  & & & Harmful in contact with skin \\  & & & May cause respiratory irritation \\  & & & Causes skin irritation \\  & & & Causes serious eye irritation \\  & & & May cause an allergic skin reaction \\ \hline \multirow{3}{*}{Potassium thiocynate} & \multirow{3}{*}{3} & Harmful if swallowed \\  & & & Harmful in contact with skin \\  & & & Harmful if inhaled \\  & & & Causes serious eye irritation \\ \hline \multirow{3}{*}{DMPA} & \multirow{3}{*}{**} & Causes serious eye irritation \\  & & & May cause respiratory irritation \\ \hline \end{tabular}  
* The toxicological properties of this substance have not been fully investigated. ** NEPA 704 health hazard division (blue) has not been found in the literature.  
\end{table} 
Table 3: Safety and health hazard information of the PCMs under study [15; 16]. A wide variety of health hazards ranging from 0 to 3 is observed. Among the sixteen materials which were evaluated, HDPE showed the lowest health hazard value in the NFPA 704 standard, meaning that it is non-hazardous under any condition. Six other materials showed a health hazard rate of 1. According to the GHS statement, these materials may cause irritation or can be hazardous at long exposure. Therefore, they are also suitable for selection but safety measures should be taken into account when using them [8].