RESUMEN
Objective To investigate the minimal persistent pigment dose (MPPD)of normal skin to UVA in Guangzhou city,and to observe its relationship to sex,age,skin type,seasons,ITA,and the years lived in Guangzhou.Methods 316 healthy subjects were exposed to Solar 601-300,and the MPPD was measured and observed by two professional technicians after 2-3 hours.Results The average MPPD value of all subjects was (9.61±2.57) J/cm2.In male and female,the average MPPD values were (11.09 ± 2.82) J/cm2 and (9.01 ± 2.20) J/cm2 respectively,and male was significantly higher than female (P＜0.01).There was significant difference of the MPPD value in different seasons (P＜0.01).The MPPD value in winter (10.66± 2.71) J/cm2) was significantly higher than spring (9.37±2.39) J/cm2,summer (9.53±2.66) J/cm2 and autumn (8.98±2.25) J/cm2.There was significant difference of the MPPD value between different ITA groups (P＜0.01).ITA grade-3 (10.72± 2.84) J/cm2 was significantly higher than grade-1 (8.50±1.45) J/cm2 and grade-2 (9.12±2.31) J/cm2 (P＜0.01),but there was no significant difference from grade-4 (11.87±2.73) J/cm2 (P =0.93).The MPPD value in subjects lived in Guangzhou over 10 years (8.97± 1.88) J/cm2 was significantly lower than those whose residence was less than 1 year and from 1 to 5 years,respectively (P＜0.01),but there was no significant difference from those lived from 5 to 10 years (P =0.47).Conclusions The MPPD value of the subjects in Guangzhou is related to gender,seasons,ITA grade and the years lived in Guangzhou city,while there is no correlation with age and skin types.