Model for projecting the generation of used disposable diapers in the era of depopulation and aging in Japan

Japan has entered a period of depopulation and aging ahead of any other country. One concern in an aging population is increases in the generation of used disposable diapers. The use of disposable diapers, which are largely composed of plastic, can be an important issue as we work towards building a carbon-free society and break away from using fossil-derived plastics. This study aimed to develop a model to project the future generation of used disposable diapers in each municipality in Japan through 2045 and to identify the effects on municipal solid waste (MSW) management. We revealed the per capita generation of used disposable diapers, distinguishing disposable diaper products, urine and faeces in an online survey of 2000 respondents. The generation of used disposable diapers was estimated to increase in general, but the amount was projected to decrease in rural areas where the population of elderly people would decline. The proportion of used disposable diapers in combustible waste was projected to increase by 2045 in almost all municipalities of Mie Prefecture. Based on the scenario in which disposable diaper products would become lighter in the future because of technical improvements, we concluded that the impact of the decrease in the lower heating value (LHV) of used disposable diapers on the incineration process cannot be ignored in the future.

Extraction and measurement of urinary tetranor-PGDM in disposable diapers

Urinary tetranor-PGDM is a useful diagnostic biomarker for food allergy which often affects infants. We attempted to extract and measure urinary tetranor-PGDM absorbed in polymer of diapers. We applied CaCl₂ to the collected polymer, determined the adequate time length of shaking the polymer to release urine, and measured tetranor-PGDM in the extracted urine. This procedure provided high linearity and recovery rate in tetranor-PGDM measurement. We also found that urinary tetranor-PGDM was stable for 24 h at 4°C in diapers. This method can be useful to monitor the food allergic condition of non-toilet trained children.

Urine collection methods for non-toilet-trained children in biological monitoring studies: Validation of a disposable diaper for characterization of tebuconazole exposure

Young children differ from adults in their exposure and susceptibility to environmental chemicals (e.g. pesticides) because of various factors such as behavior, diet and physiology. Their heightened vulnerability to environmental stressors makes it important to obtain appropriate urine samples for exposure characterization. However, collecting urine from non-toilet-trained children has been shown to be methodologically and practically challenging. Four urine collection approaches were tested: a disposable diaper, a urine bag, a collection pad and the clean catch. The success rate and the user rating of each method was evaluated. The success rates were 67%, 21%, 17% and 4% for the disposable diaper, urine bag, collection pad and clean catch, respectively. The average user ratings on a 0-10 (0 = inconvenient, 10 = convenient) scale were 9.0, 4.7, 7.3 and 2.5, respectively. Subsequently, the best rated method, the disposable polyacrylate diaper was tested with hydroxy-tebuconazole as an exposure biomarker for the fungicide tebuconazole and creatinine for urine density adjustment. After LC-MS/MS analysis, the recoveries of hydroxy-tebuconazole in the range of 0.05-25 ng/mL were on average 106%, and for creatinine 87%. Precisions (relative standard deviation) were for both 3%. The overall procedure including collection and extraction was assessed, resulting in three out of seven positive samples. Based on this study, the disposable diaper is a suitable method for urine collection of non-toilet-trained children for biomonitoring of tebuconazole. This method can serve as a basis for extension to other substances of interest.