1.What is exposure assessment?
Exposure assessment is an important part of cosmetic safety assessment. According to the definition in the Cosmetic Safety Assessment Technical Guidelines (hereinafter referred to as the Guidelines) issued by NMPA, exposure assessment refers to determining the exposure level of cosmetic raw materials or risky substances by evaluating the location, concentration, frequency and duration of exposure to the human body. Its purpose is to quantify the exposure of the human body to cosmetic raw materials and/or risky substances and provide a basis for cosmetic safety assessment.
2. What is the significance of exposure assessment?
In cosmetics, even if an ingredient itself is potentially toxic, as long as the amount of exposure after use is below the toxic effect threshold, the possibility of causing harm to human health is acceptable.
For example, phenoxyethanol, a commonly used preservative in cosmetics, may cause neurotoxicity and hepatotoxicity when taken in large doses, but the "Cosmetic Safety Technical Specifications" stipulates that the maximum allowable concentration of cosmetics when used shall not exceed 1%. This limit is obtained by comparing the toxic effect threshold and the cumulative exposure. Through exposure assessment, it can be determined whether the ingredients in cosmetics are within the safe range.
In addition, exposure assessment can also help products formulate usage recommendations. If the exposure assessment shows that the exposure of a certain ingredient is close to the safe upper limit, it is necessary to reduce the concentration of the ingredient, or limit the amount or frequency of use. For example, some sunscreens recommend that the maximum number of uses per day should not exceed twice.
3. Exposure assessment plan in the Guidelines
According to the Guidelines, when conducting exposure assessment, factors such as the concentration, site of use, amount of use, frequency of use, and duration of use of products containing the raw materials or risk substances need to be considered.
4. Selection of exposure assessment data
■ Research on exposure parameters in China
China has now begun to gradually pay attention to the collection and analysis of localized data. The Shanghai Center for Disease Control and Prevention has published the "Usage Status of Common Leave-on Cosmetics Used by Women in Shanghai and Analysis of Some Key Exposure Parameters" in 2024.
Through a survey and follow-up of 309 Shanghai women aged 22 to 60, key parameters such as daily usage and each usage were given through statistical analysis.
In addition, women aged ≥45 years old use significantly higher frequency and amount of skin care lotion and serum than those aged <45 years old; while different skin types or skin sensitivities have no significant impact on daily or per-time use amounts.
These data fill the gap in domestic exposure assessment of leave-on cosmetics and further prove the significant differences between Chinese consumers and foreign people in terms of cosmetics usage habits and exposure levels. The research results also show that the local population's use of cosmetics is generally lower than foreign reference data. If foreign exposure parameters are directly used for evaluation, inaccurate conclusions may be drawn.
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