Comparison of International Guidelines of Dermal Absorption Tests Used in Pesticides Exposure Assessment for Operators

Abstract

The number of farmers who have suffered from non-fatal acute pesticide poisoning has been reported to vary from 5.7% to 86.7% in South Korea since 1975. Absorption through the skin is the main route of exposure to pesticides for farmers who operate with them. Several in vitro tests using the skins of humans or animal and in vivo tests using laboratory animals are introduced for the assessment of human dermal absorption level of pesticides. The objective of this study is to evaluate and compare international guidelines and strategies of dermal absorption assessments and to propose unique approaches for applications into pesticide registration process in our situation. Until present in our situation, pesticide exposure level to operator is determined just using default value of 10 as for skin absorption ratio because of data shortage. Dermal absorption tests are requested to get exposure level of pesticides and to ultimately know the safety of pesticides for operators through the comparison with the value of AOEL. When the exposure level is higher than AOEL, the pesticide cannot be approved. We reviewed the skin absorption test guidelines recommended by OECD, EFSA and EPA. The EPA recommends assessment of skin absorption of pesticides for humans through the TPA which includes all the results of in vitro human and animal and animal in vivo skin absorption studies. OECD and EFSA, employ a tiered approach, which the requirement of further study depends on the results of the former stage study. OECD guidelines accept the analysis of pesticide level absorbed through skin without radioisotope when the recovery using the non-labeled method is within 80~120%. Various factors are reviewed in this study, including the origin of skin (gender, animal species and sites of skin), thickness, temperature and, etc., which can influence the integrity of results.

Sanitary pads and diapers contain higher phthalate contents than those in common commercial plastic products

“…Because the top sheet of the diaper is in direct contact with the external genitalia of the newborn, phthalates in the top sheet can be absorbed into the skin and adversely impact the development and function of the reproductive and urinary systems. Compared to other parts of human body, scrotum showed the highest dermal absorption rate for parathion (4 ppm in acetone) with a 5.5-fold and 9.1-fold increased absorption rates when compared to abdominal skin and palm, respectively [64]. Vulvar tissue is more permeable to most of chemicals than other skins due to it is hydrated, thin and extensively vascularized [17].…”

Assessment of occupational exposure to pesticides applied in rice fields in developing countries: a critical review

“…Hence, the respective exposure levels are typically adjusted using absorption factors. Dermal absorption via the skin surface is known to be a function of the percentage of active substance in the product; for example, the European Union risk assessment scheme assumes absorption factors of 25 and 75% for pesticide products that contain >5 and 5% of the active substance(s), respectively (EFSA 2012;So et al 2014). Respiratory inhalation can be particularly dangerous due to the likelihood of a higher percentage absorbed dose, so risk assessment schemes often adopt a worst-case assumption of 100% absorption of all inhaled chemicals by the body (Kegley and Conlisk 2010;Lee et al 2018).…”

Chlorpyrifos Induced Dermal Toxicity in Albino Rabbits

“…Chlopyrifos is lipophilic in nature and its dermal toxicity profiling has not yet been extensively explored. It is thought that some of the insecticides disrupt the uppermost layer of skin (Stratum corneum of the epidermis) and facilitate their absorption and hence induce toxicity to keratinocytes (So et al, 2004). The physicochemical nature and the vehicle are the two important factors that are responsible for toxic insult and dermal absorption.…”