Table 1.

Condensed description of the six studies in category A and extracted specific hazardous dwelling condition characteristics from each study.

Characteristics	Condensed Description
Mold Cockroach infestation Peeling paint Rodent infestation (NS) Rotting wood (NS) Leak under sink (NS) Pesticides (NR) Note: several characteristics associate with each other, e.g., mold and cockroach.	Bradman et al. (2004) [21]. Environmental assessments were carried out in 644 homes of pregnant Latina women and their children in an agricultural community in California between October 1999–2000. Participants were recruited via a health clinic serving predominantly low-income Latina clients. Most homes (85%) had four or more household members, and 69% of the homes housed at least one agricultural worker. A large portion (39%) of the homes were crowded, i.e., had more than 1.5 persons per room, and were in bad condition: 58% had peeling paint, 43% had mold, 25% had water damage, and 11% had rotting wood. About half of the families used pesticides in their homes, mainly pyrethroid insecticide sprays and powders. Cockroaches and rodents were present in 60% and 32% of the homes, respectively. Crowded living (more than 1.5 persons per room) was significantly associated with cockroach infestation (odds ratio (OR) 2.7, p < 0.01), peeling paint (OR 2.2, p < 0.01) water damage (OR 2.5, p < 0.05, and mold (OR 1.9, p < 0.05) and weakly (non-significantly) related to rodent infestation (OR 1.1) rotting wood (OR 1.2), and leak under sink (OR 1.1). There were also significant associations between rodent or cockroach infestation and a number of home conditions: peeling paint, water damage, mold (rodent only), and level of cleanliness.
Cockroach allergen Dust mite allergen	Leaderer et al. (2002) [59]. Dust samples were collected in the living areas of 999 homes of asthmatic children in southern New England, USA, 1996–1998, and analyzed for dust mite, cockroach, cat, and dog allergens. Data on maternal education, income, race, dwelling type (single or multi-family household), population density (people per square mile), and household density (people per room) were collected by home interviews and census data. Logistic regression analyses revealed significantly increased odds ratios for elevated levels of cockroach allergens but lowered levels of mite allergens in low income, black and Hispanic, multi-family, and crowded households (more than one person per room).
Mold Note: cockroach appears to be a common characteristic but is not measured.	Richter et al. (2018) [82] conducted a cross-sectional study among immigrant families in Sweden to assess the contribution of bad housing conditions to poor health. Families were recruited via identification of children with respiratory problems. In all, 130 families (650 individuals) were included. Data on living and dwelling conditions were obtained by the combination of questionnaires and home inspections. Eighty-four of the households were classified as crowded (more than one person per bedroom), and crowdedness was significantly associated with subjective as well as objective reports of dampness and mold. In addition, 416 of the 650 participants underwent skin prick tests against common aeroallergens, including molds, house dust mites, plants, and animal dander, and to cockroach antigen. Crowdedness did not significantly influence the children’s risk for being sensitized overall. However, participants showing sensitization against cockroach allergen (11 in total) were much more likely to live in an apartment with cockroach exposure (p = 0.006) than non-sensitized participants, and all homes with children sensitized against cockroach antigen (5 in total) had cockroach infestation in the past.
Mold	Howden-Chapman et al. (2005) [49] undertook a random telephone survey regarding mold and its risk factors in New Zealand houses. In total, 613 household responded (response rate 50.5%). Multivariate analysis revealed that a number of house construction and climate and behavioral factors were significantly related to reported mold, including older house, lack of sun exposure, no insulation, high locality rainfall, living in the north of the country and frequent baths, showers, and clothes washing. With respect to crowdedness, the analysis revealed significant positive relations between the prevalence of mold and number of residents, number of residents below 18 years old, and number of residents per bedroom. With respect to the latter, the prevalence of mold was 29% for less than 1 resident, 34% for 1–1.5 residents, and 48% for more than 1.5 residents per bedroom.
Microorganism distribution (fungi, dust mite, and bacteria) Note: pesticide use was measured, considered necessary to explain microorganism distribution, but results were not presented.	Rocchi et al. (2015) [85] studied the microorganism composition in dust collected from 3193 French dwellings 2011. Dwellings were recruited via a subsample (EBRA, microbiological environment, and allergic risk) of the Elfe cohort (a large cohort devoted to monitoring children’s development from birth to adulthood). The analyses included six fungal species, three families/genera of bacteria, and house dust mite. Data on 13 dwelling characteristics were collected, namely dwelling type (apartment or house), family situation (owner, tenant, and free), pets, dwelling renovation, pesticide use and potted plants (yes and no), daily housework time, floor covering in bathroom, kitchen and living room (tile, linoleum, parquet, and other), window number, floor number, and occupation ratio (inhabitants per m2). Of these characteristics, occupation ratio, dwelling type (house/apartment), and presence/absence of pets were significantly related to the microorganism distribution in the dwellings, although they only explained a small fraction of the variance (3%). Dust mite; Enterobacteriaceae; and to a lesser extent, C. sphaerospermum were mainly associated with occupation ratio.
Lead in house dust Cadmium in house dust	Meyer et al. (1999) [69] measured lead and cadmium in house dust collected for one year (starting October 1993–August 1994) from 415 dwellings located in different industrial areas in eastern Germany. Lead and cadmium deposition rates (expressed as µg/m2 per day) were significantly associated with area of residence, urban environment (park, side road, main road, and industrial), type of heating (central/district heating, gas, coal), year of construction, and crowding. Regarding crowding, the average deposition rates were 61% (lead) and 80% (cadmium) higher in sampling rooms with three or more persons, compared to rooms with no persons.

NS, not significant, NR, not reported.