Household products are widely and regularly used by consumers; members of the general public may be exposed to hazardous chemicals by intentionally using products (for example non-professional users) that are intended to improve users’ living and sanitary conditions. The public may also be exposed to “unintentional use” when they are present when others use such products for household cleaning and personal care (Nilsen et al., 2002; ECHA, 2013). Therefore, consumers of household products are exposed to several kinds of substances on a daily basis  (Wolkoff and Nielsen, 2017). Public interest in and awareness of the health impacts of exposure to multiple chemicals continues to grow as more information is gathered from several sources including personal care and household products (U.S.EPA, 2007). In the United States, organizations such as the Environmental Protection Agency (EPA) and the Agency for Toxic Substances and Disease Registry (ATSDR) have developed documents that support the development of aggregate risk assessment (ATSDR, 2002; U.S.EPA, 2002, 2003).

The EPA defined the  general  concepts  and  and identified specific elements of and approaches for considerations for aggregate risk assessment implementing aggregate risk assessments (U.S.EPA, 2002, 2003). Aggregate risk assessment is an analysis, characterization, and possible quantification of the combined risks to health or the environment from multiple chemicals or stressors. The exposure assessment to chemicals from several resources including household products is suspected to be the cause and the initial goal of the investigation into the identification of health effects (U.S.EPA, 2003, 2007). To conduct an exposure assessment for using household products, it is necessary to gain information on aggregate exposure (for example frequency of aggregate use and information about the circumstances of usage) (Van Engelen et al., 2007). Several studies on exposure information associated with household products were conducted. A European household product database for domestic use of 15 products was established to provide information that would enable exposure and risk assessment of the chemicals included in common household products (Dimitroulopoulou et al., 2015a; Dimitroulopoulou et al., 2015b; Trantallidi et al., 2015). In the USA, the study of use of products and exposure-related behaviors project provided data on usage patterns for many household products (Bennett et al., 2010). Exposure patterns may vary by country (Biesterbos et al., 2013; Park et al., 2015; Garcia-Hidalgo et al., 2017; Park et al., 2017). A national database of aggregate exposure information for household products is essential to conduct aggregate exposure and risk assessments.

In Korea, disinfectants were used in humidifier water tanks in order to prevent the growth and spread of germs, molds, and/or algae. The inhalation of aerosolized water from a humidifier that contained disinfectants led to serious lung issues that resulted in 200 deaths and 700 injuries, including children (Park et al., 2013). This tragedy heightened public attention and raised concerns. In 2013, the Korean government enacted regulations on substances in a variety of household products that may adversely affect health in an effort to promote the safe use of these products [The Korean Registration, Evaluation, Authorization and Restriction of Chemicals (K-REACH)] (Lee et al., 2012). Household products that fall under these regulations are required to be assessed for exposure and risk in order to evaluate the health and environmental hazards associated with their use.

The purpose of this present study was to develop a database on aggregate exposures for 11 product categories and 40 products usage to consumers. The exposure information data determined in this study will be useful in establishing more improved safety guidelines for household products.

This study analyzed the co-use and multiple-use pattern of 11 household products collected from survey study of 6,397 respondents that carried was out over two years (2016−2017) in 15 metropolitan areas and provinces including  rural  areas  in Korea (Kim et al., 2019). The previous study investigated a national exposure factor database to be used in exposure assessment and risk assessment of household products to human health. This database includes the following information that is necessary for exposure assessments of household products: frequency of use, duration of use, amount of use, and emission amount of use per application. Reliable exposure factors derived from our previous study were established in notification by the National Institute of Environmental Research NIER (KNLIC, 2017; NIER, No. 2017-55); thus, because exposure factors differ by country, Korean exposure factors were specified in the law. Based on surveyed data, in this study, the co-use and multiple-use were analyzed.

Study population and surveys

To analyze the co-use and multiple-use combination of household products, the results from two web surveys were used. The first survey involved six products: a cleaner, an adhesive, a polishing and coating product, a synthetic detergent, a fabric softener, and a bleaching agent used by 3,397 participants. The second survey involved an air freshener, a deodorant, an ironing auxiliary, an algae remover, and a home printer used by 3,000 participants. Each web survey collected current information on the use pattern for eleven product categories through the survey questions (Table A1 and A2).

Studied household product categories

Among the product categories established by the Korean Ministry of the Environment (KMOE) as risk-concerned products for residential consumers (KNLIC, 2017; KMOE, No. 2017-153), 11 household products were selected in this study (Table A1). Usage information of the product categories studied was collected from a market survey conducted to elucidate which products are commonly used in the Korean market. Based on the results of the survey, 40 usages (purpose of product) of 11 product categories were divided (12 usages for cleaners, three usages for adhesives, eight usages for polishing and coating products, one usage for synthetic detergent, one usage for fabric softener, one usage for bleaching agent, two usages for air freshener, eight usages for deodorant, one usage for ironing auxiliaries, two usages for algae remover, and one usage for home printers). The products that were studied and their usage categories were classified according to the following: products representative of those used on a daily basis by adult male and/or female consumers, products accounting for a major part of exposure from household products, and adequate available data such as exposure factors (frequency of use, duration of use, and amount of use) on product use and typical consumer habits. The household products included in this study were commonly used by adults, and so participants were at least 19 years of age. The list of products and categories of product use are shown in Table 1.

Co-use and multiple-use patterns of products

Exposure of consumers to household products by co-use and multiple-use products is likely described as combined exposure by consumers of multiple ingredients in products. This study used data on combined exposure of consumers to multiple household products through product use. These data were investigated to determine the aggregate consumer risk assessment. To evaluate co-use and multiple-use patterns of products and products usage categories, the responses to the questionnaire were divided into single use of one product, co-use of two products, and multiple-use of several products. Co-use was defined as regular use of two products (or two product uses), and multiple-use was defined as regular use of more than two products (from using three or more products). In the first survey, the responses for six products (cleaner,  adhesive,  polishing and  coating product,  synthetic detergent, fabric softener, and bleaching agent) by 3,397 respondents were analyzed. In the second survey, the responses for five products (air freshener, deodorant, ironing auxiliary, algae remover, and home printer) by 3,000 respondents were analyzed.

Calculating the combined exposure amount

Considering the worst-case scenario, the combined used amount of products by respondents that used multiple products was calculated as the exposed amount to products. Exposure factor values for each household product (single use by consumers) were used to calculate the aggregate exposure amount, based on the usages and their application types. Reference reliable exposure factors of Korean consumers were already established by the NIER (KNLIC, 2017(NIER, No. 2017-55); Kim et al, 2019). Reference exposure factors for household products consists of the frequency of use, the duration of use, and the amounts of use per application divided by usages and their application types. Korean exposure factors are specified by law, and exposure scenarios for household products based on several exposure routes are also specified, with different countries exhibiting different exposure factors. On the basis of these exposure factors, the amount of exposure to studied products per month was calculated. As a result of market survey, eleven products were categorized to several usages (purpose of product) and furthermore, each usage of products was divided to their application types.

This approach investigated the available data for the aggregate exposure assessment. Combined exposure of multiple ingredients in household products  by  the multiple-use pattern of consumers was analyzed. This information might be useful in conducting aggregate exposure assessments to consumers and aggregate risk assessment to human health.

Surveys and single-use prevalence of products

On the basis of the market survey results to elucidate the household products and products usage categories that are commonly used, the 11 product categories mentioned above were divided into several uses: for example use toilet and bathroom and for home glass cleaning in cleaner, all-purpose use in adhesive, and use on fabric in deodorant (Table 1). Overall, 6,397 participants completed the use-pattern web surveys, of which 53.2% (n=1805) in the first survey and 53.3% (n=1,600) in the second survey were females (Table A1). The prevalence of product use was defined as the number of users who reported the use of studied household products in the two years prior to the study. The surveyed respondents had more than one product among each product groups at home and regularly used nearly all of the studied products groups as a high ratio (Tables 2 and 3).

In the 1^st survey, the percentages of respondents using products (a single use) were 75.3% (2559 respondents/3397 participants, cleaner), 42.1% (adhesive), 40.1% (polishing and coating products), 65.1% (synthetic detergent), 68.4% (fabric softener), and 30.2% (bleaching  agent) (Table 2). In the second  survey, the percentages of respondents using products (a single use) were 73.2 (2,559 respondents/3,397 participants), 69.0, 11.6, 18.9, and 67.7% for air freshener, deodorant, ironing auxiliary, algae remover, and home printer (Table 3). Among the product categories studied, bleaching agent, ironing auxiliary, and algae remover showed relatively low use rates among less than 40% of respondents. In contrast, cleaner, synthetic detergent, fabric softener, air freshener, deodorant, and home printer exhibited comparatively high use rates, involving more than 60% of respondents for each. The product showing the highest use rate was cleaner (Tables 2 and 3). Gender variations (male and female) for single-use pattern of studied products in the first and second surveys were presented in Tables 5 and 6. In the case of cleaner, adhesive, synthetic detergent, fabric softener, bleaching agent, air freshener, and deodorant, females showed higher use rate than males (the rate of single use).

Co-use pattern of products

The co-use rates of two studied products were analyzed. Co-use of products that contain the same ingredients results in aggregate exposure to those ingredients. Therefore, it is necessary to understand the key patterns of current use of different household product categories to calculate the aggregate exposure (Garcia-Hidalgo et al., 2017). Co-use analysis of 11 product categories was performed for all 6,397 respondents. In Table 2, all possible co-use and multiple-use combinations of product categories introduced in the first survey are presented. Among users of cleaner (2,559 respondents), the percentages of co-use were as follows: cleaner and adhesive co-users (48.9%), cleaner and polishing and coating products co-users, (47.1%), cleaner and synthetic detergent co-users (72.0%), cleaner and fabric softener co-users (75.3%), and cleaner and bleaching agent co-users (36.3%). Table 3 shows all possible co-use and multiple-use combinations of product categories in the second survey. The percentages of co-use among users of air freshener (2,197 respondents) were as follows: air freshener and deodorant co-users (72.1%), air freshener and ironing auxiliary (12.8%), air freshener and algae remover (22.0%), and air freshener and home printer (71.6%). Gender variations (male and female) in co-use patterns of the products studied in the first and second surveys are presented in Tables 5 and 6. The co-use rate was somewhat complicated between females and males. Studied products that showed high single-use rates also showed high concurrent co-use rates.

Multiple-use pattern of products

The multiple-use rate of products varied according to products and the purpose for use. Tables 2 and 3 show the combination and the rate of multiple-use (six products in the first survey, and five  products  in  the second survey). These results addressed the combination exposure of multiple products and multiple ingredients to consumers. The multiple-use pattern by users might be helpful in carrying out a general approach for combined exposure- and risk-assessment of multiple ingredients that could be adapted to the needs of users. Gender variations for multiple-use patterns of studied products in the first and second surveys were also presented in Table 5 and Table 6. In case of cleaner use among female users, the multiple-use rate of cleaner, synthetic detergent, and fabric softener was the highest at 50.8%. Also, multiple users of all six products in the first survey showed a rate of 8.7% (Table 5). In the case of air freshener use among female users, the multiple-use rate of air freshener, deodorant, and home printer was the highest at 39.2% (Table 6).

Combined exposure amount of products

The multiple used amounts of respondents to household products at home were investigated. Table 4 presents amounts each product used divided by usages (purpose of product) from single use at home by respondents. Table 4 shows the products categories, their usages, and their application types. In order to calculate the use amount of household products from single use by respondents, we summed up the use amount (g/use) of all application types of each product divided by usages. After then, the use amounts per month were calculated (g/month). The mean use amount per use and per month differed among products (Table 4). The mean use amount of cleaner products was found to be 3614.4 g/month (Table 5). The aggregate amount of cleaner, adhesive, polishing and coating product, synthetic detergent, fabric softener, and bleaching agent was calculated as 7479.6 g/month (Table 5). Tables 5 and Table 6 summarized the combined aggregate use amount of six products (target products in 1^st survey) and five products (target products in 2^nd survey). In order to study exposure assessment, exposed amount to user could be calculated with values of used amount of products by user. The information of aggregate exposure amount used by users might be helpful in carrying out the approach for aggregate exposure assessment study.

Co-use pattern of products divided by usage

In Tables 7 and 8, the single-use and co-use prevalence of products divided by uses were analyzed as the numbers of respondents who did respond to the use of single- and two-product usages. According to the survey results, there were 40 usages of the studied 11 product categories mainly in the Korean market. Respondents retained several usages’ products from each product category. A cleaner had 12 main usages: for toilet and bathroom, cleaning glass, cleaning the kitchen, cleaning mold and moss, cleaning the floor of a building,  and others. Also, deodorants with eight kinds TB, cleaner for toilet and bathroom; CG, cleaner for glass; CK cleaner for kitchen; cleaner for mold and moss; CF, cleaner for floor of building; cleaner for carpet; cleaner for air-conditioner; CW, cleaner for washing machine; RS, cleaner for removing sticker; CD, cleaner for drainpipe; CP, cleaner for metal products; CV, cleaner for vehicle inside and outside; MP, adhesive for multiple-purpose; DE, adhesive for double eyelid and eyebrow extension and eyelashes; N, adhesive for nails; PF, polishing and coating product for furniture; PS, polishing and coating product for shoes; WR, polishing and coating product for water-repellent of fabric; MW, polishing and coating product for multiple-purpose water-repellent; WV, polishing and coating product for water-repellent of vehicle glass; PC, polishing and coating product for car inside; PO, polishing and coating product for car outside; WT, polishing and coating product for wheel and tire of vehicle; LF, synthetic detergent for fabric; F, fabric softener for fabric; FS, bleaching agent for fabric and shoes; IA, air-freshener for indoor air; VA, air-freshener for vehicle air; FA, deodorant for fabric; FS, deodorant for shoes; FI, deodorant for indoor air; FV, deodorant for vehicle air; FC, deodorant for clothes case; FR, deodorant for refrigerator; FT, deodorant for toilet; AC, deodorant for air-conditioner; FF, ironing auxiliaries for fabric; FT, algae remover for fish tank; SA, algae remover for stone article; HP, home printer. ^a experimented mean weight of products from using each product by respondents, ^b mean amount of products single-used by consumers were evaluated as KNLIC-2017 (NIER No. 2017-55) and Kim et al (2018), ^c calculated mean summed weight of products per month (30 days). of usages were mainly sold in the Korean market. The use rates of cleaner usage categories divided by the number of uses (a single use) in the first survey were: for toilets and bathrooms (45.7%), for cleaning glass (32.5%), for cleaning the kitchen (42.5%), for cleaning mold and moss (23.7%), for cleaning the floor of a building (6.8%),  for  cleaning  carpets  (1.8%),  for cleaning air conditioners (6.1%), for cleaning washing machines (15.1%), for removing  stickers  (4.2%), for cleaning drainpipes (15.0%), for cleaning metal products (4.4%), and for cleaning the inside and outside of vehicles (9.6%) (Table 7). The use rates of other product categories divided by usages in the first survey (three for adhesive, eight for polishing and coating products, one for synthetic detergent, one for fabric softener, and one for use as a bleaching agent) are shown in Table 7. Product usage categories of the second survey were two usages for air freshener, eight for deodorant, one for ironing auxiliaries, two for algae remover, and one for home printer. In the case of air freshener, the use rates of respondents using two usages products were 64.7 and 41.1% for use of indoor air and use of vehicle air, respectively. The single-use rates of deodorant usage categories were as follows: use of fabric (77.5%), use of shoes (15.3%), use of indoor air (18.3%), use of vehicle air (21.1%), use of clothes closet (32.3%), use of refrigerator (19.1%), use of toilet (28.5%), and usage of air conditioner (12.7%) (Table 8). In Tables 7 and 8, all possible co-use combinations of product usage categories in the two surveys are presented. Among cleaner, products for toilet and bathroom, products for cleaning home glass, and products for cleaning kitchens exhibited relatively high co-use rates among respondents. In the case of adhesive, its co-use rate for multi-purpose products was comparatively high. In case of synthetic detergent and fabric softeners, 1,847 (54.4%) of the 3,397 respondents had co-use habits involving those two products (Table 7).

Systemic evaluation of the aggregate health risks from the combined effects of multiple products and chemicals is becoming a vital component of risk-based decisions aimed at  protecting  consumers. The  process  of assessing risk to humans of household products entails a sequence of actions relevant to human health, such as identification of hazardous substances in products, characterization of these substances, exposure assessment, and risk characterization (ECHA, 2012, 2013, 2016). The current study investigated the exposure database of single-use patterns and reliable exposure factors concerning household products (Kim et al., 2019). The current study provides data on the co-use and multiple use of 11 household products and 40 uses of 11 products. In addition, the rates of single-use, co-use, and multiple-use by respondents were analyzed. Relatively high rates of respondents used combinations of two or more products, for example, a cleaner and an adhesive or a cleaner and a synthetic detergent. The estimation of consumer exposure to household products is a fundamental element of the risk assessment process and requires quantification of the levels of exposure for consumers (non-professional users) to household products (ECHA, 2016). Such a consumer exposure assessment should normally address the intended uses of the product. An important component of current exposure and risk assessment is the consideration of aggregate and aggregate exposures. When assessing exposure and health risk to consumers, more accurate exposure assessment could be estimated by cumulated and aggregated exposures from all potential exposure routes (Sexton, 2012). The aim of this study was to create the sufficient exposure information for implementing aggregate exposure and health risk assessment of household products. This study analyzed the current multiple-use patterns of household products by surveying via the web over 6,000 consumers in Korea. This study of aggregate exposure information for household products suggests potential  health  risk  concerns among adult consumers and unintentionally exposed children. This information includes the combined multiple-use pattern, which is needed for aggregate exposure assessments of household products. Co-use and multiple-use patterns of household products by consumers are to the aggregate multiple exposures of products and  of  multiple ingredients in products. Multiple exposures by several product categories could address the combined exposure to multiple chemicals. Because of the unidentified fatal lung disease caused by chemical disinfectants used in household humidifiers in Korea, KMOE and NIER conducted human risk assessment studies to assess levels of hazardous ingredients in consumer products.

The KMOE has established safe guidelines for consumer products and is regulating ingredients in consumer products strongly (KNLIC, 2017; KMOE, No. 2017-153). However, aggregate exposure evaluations of chemicals used in household products have remained a grey area in chemical management in Korea. According to numerous international organizations, such as the EPA and WHO, aggregate risk assessments are intended to answer difficult and formerly unaddressed questions regarding combined risk burdens and disproportionate health impacts. Also, such assessments tend to be more theoretically complex, methodologically complicated, and challenging than traditional single-chemical assessments (U.S.EPA, 2003, 2007). At present, KMOE and NIER pay a great deal of attention as they conduct aggregate health risk assessment studies to assess combined chemicals from possible routes. Therefore, as a further study, we are investigating the combined exposure and health risk assessment study to primary and secondary users.

This study provides valuable information on the individual use patterns and circumstances of household products used by Korean adult consumers. A database might be helpful to conduct aggregate exposure assessment for ingredients that are components of household products.

This research was supported entirely by a grant from the National Institute of Environment Research (NIER), funded by the Korean Ministry of Environment (KME) of the Republic of Korea (NIER-2016-01-01-122 and NIER-2017-01-01-012).

The authors have not declared any conflict of interests.