Dampness, indoor mould, fungal DNA and respiratory health - molecular methods in indoor epidemiology

Visible damp in a child's bedroom is associated with increased respiratory morbidity in early life: a multicentre cohort study

OBJECTIVE

Household damp exposure is an important public health issue. We aimed to assess the impact of the location of household damp on respiratory outcomes during early life.

METHODS

Household damp exposure was ascertained in children recruited to the GO-CHILD multicentre birth cohort study. The frequency of respiratory symptoms, infections, healthcare utilisation and medication prescription for wheezing were collected by postal questionnaires at 12 and 24 months. Log binomial and ordered logistic regression models were fitted to the data.

RESULTS

Follow-up was obtained in 1344 children between August 2010 and January 2016. Visible damp was present in a quarter of households (25.3%) with 1 in 12 children's bedrooms affected (8.3%). Damp in the bathroom, kitchen or living room was not associated with any respiratory or infection-related outcomes. Damp in the child's bedroom was associated with an increased risk of dry cough (8.7% vs 5.7%) (adjusted relative risk 1.56, 95% CI 1.07 to 2.27; p=0.021) and odds of primary care attendance for cough and wheeze (7.6% vs 4.4%) (adjusted OR 1.37, 95% CI 1.07 to 1.76; p=0.009). There were also increased risk of inhaled corticosteroid (13.3% vs 5.9%) (adjusted RR 2.22, 95% CI 1.04 to 4.74; p=0.038) and reliever inhaler (8.3% vs 5.8%) (adjusted RR 2.01, 95% CI 1.21 to 2.79; p=0.018) prescription.

CONCLUSION

Damp in the child's bedroom was associated with increased respiratory morbidity. In children presenting with recurrent respiratory symptoms, clinicians should enquire about both the existence and location of damp, the presence of which can help prioritise those families requiring urgent household damp assessment and remediation works.

AWMF mold guideline "Medical clinical diagnostics for indoor mold exposure" - Update 2023 AWMF Register No. 161/001

None.

Association of indoor microbial aerosols with respiratory symptoms among under-five children: a systematic review and meta-analysis

BACKGROUND

Despite the recognition of the importance of indoor microbial exposures on children's health, the role of different microbial agents in development and aggravation of respiratory symptoms and diseases is only poorly understood. This study aimed to assess whether exposure to microbial aerosols within the indoor environment are associated with respiratory symptoms among children under-5 years of age.

METHODS

A systematic literature search was conducted on PubMed, Web of Science, GreenFILE, ScienceDirect, EMBASE and Cochrane library through February 2020. Studies that investigated the exposure-response relationship between components of the indoor microbial communities and respiratory symptoms among under-five children were eligible for inclusion. A random-effect meta-analysis was applied to estimate pooled relative risk (RR) and 95% confidence interval (CI) for study specific high versus low microbial exposures. The potential effect of individual studies on the overall estimate was evaluated using leave-one-out analysis, while heterogeneity was evaluated by I² statistics using RevMan 5.3.

RESULTS

Fifteen studies were eligible for inclusion in a meta-analysis. The pooled risk estimate suggested that increased microbial exposure was associated with an increased risk of respiratory symptoms [pooled relative risk (RR): 1.24 (1.09, 1.41), P = 0.001]. The association was strongest with exposure to a combination of Aspergillus, Penicillium, Cladosporium and Alternaria species [pooled RR: 1.73 (1.30, 2.31), P = 0.0002]. Stratified analysis revealed an increased risk of wheeze [pooled RR: 1.20 (1.05, 1.37), P = 0.007 and allergic rhinitis [RR: 1.18 (0.94, 1.98), P = 0.16] from any microbial exposure.

CONCLUSIONS

Microbial exposures are, in general, associated with risk of respiratory symptoms. Future studies are needed to study the indoor microbiome more comprehensively, and to investigate the mechanism of these associations.

Household dampness and microbial exposure related to allergy and respiratory health in Danish adults

Background: Indoor dampness has consistently been associated with respiratory symptoms and exacerbations. The causal mechanisms may involve increased microbial exposures. However, the evidence regarding the influence of indoor microbial exposures under damp- and non-damp conditions on the risk of asthma and allergy has been inconclusive. Objective: The aim of this study was to investigate the association between dampness and microbial exposure with allergy and respiratory health in Danish adults using a cross-sectional design. Methods: From 1,866 participants of the Health2006 cohort, we selected three non-overlapping groups: 196 at random, 107 with confirmed atopy, and 99 without atopy. Bedroom dust was sampled using electrostatic dust fall collectors and analysed for endotoxin, β-(1,3)-D-glucan, 19 microbial species or groups, and total fungal load. Household moisture-related problems and asthma were self-reported by questionnaire. Atopy was determined by skin-prick-testing and lung function was measured by spirometry. Results: Household moisture damage was positively associated with asthma outcomes, although this was statistically significant only in atopics for self-reported asthma (odds ratio (OR) 3.52; 95%CI 1.01-12.7). Mould odor was positively associated with wheezing (OR 6.05; 95%CI 1.19-30.7) in atopics. Inconsistent associations were found for individual microbial exposures and health outcomes. Inverse associations were observed between microbial diversity and rhinitis in the random sample and both doctor-diagnosed and self-reported asthma in non-atopics. Conclusions: In conclusion, our findings suggest that household moisture damage may increase the risk of asthma and wheeze with mould odor in atopics. In addition, asthma and allergy may be affected by the indoor microbial composition in urban domestic environments. Further studies are needed to identify and understand the causal agents and underlying mechanisms behind the potential effects of environmental microbial exposure on human health.

Microbial Agents in the Indoor Environment: Associations with Health

There is international consensus that damp buildings and indoor mould can increase the risk of asthma, rhinitis, bronchitis and respiratory tract infections but we do not know which types of microbial agents that are causing the observed adverse health effects. Microbial indoor exposure is a broader concept than microbial growth in buildings. Other sources of indoor microbial exposure include the outdoor environment, humans (crowdedness) and furry pet keeping. Microbial exposure can have different health effects depending on the dose, different exposure route, genetic disposition and the timing of exposure. Microbial stimulation linked to large microbial diversity in early life can protect against disease development, especially for allergic asthma and atopy. Protective effects are more often reported for bacterial exposure and adverse health effects are more often linked to mould exposure. There are many studies on health associations for indoor exposure to endotoxin, mainly from homes. The risk of getting atopic asthma may be less if you are exposed to endotoxin in childhood but the risk of non-atopic asthma may increase if exposed to endotoxin especially in adulthood. Moreover, genetic disposition modifies health effects of endotoxin. Epidemiological studies on muramic acid (from gram-positive bacteria) or ergosterol (from mould) are few. Studies on health effects of indoor exposure to beta-1-3-glucan (from mould) have conflicting results (positive as well as negative associations). Epidemiological studies on health effects of indoor exposure to mycotoxins are very few. Some studies have reported health associations for MVOC, but it is unclear to what extent MVOC has microbial sources in indoor environments. Many studies have reported health associations for fungal DNA, especially as a risk factor for childhood asthma at home. Since most studies on health effects of indoor exposure to mould, bacteria and microbial agents are cross-sectional, it is difficult to draw conclusions on causality. More prospective studies on indoor microbial exposure are needed and studies should include other indoor environments than homes, such as day care centers, schools, hospitals and offices.

Indoor visible mold and mold odor are associated with new-onset childhood wheeze in a dose-dependent manner

Evidence is accumulating that indoor dampness and mold are associated with the development of asthma. The underlying mechanisms remain unknown. New Zealand has high rates of both asthma and indoor mold and is ideally placed to investigate this. We conducted an incident case-control study involving 150 children with new-onset wheeze, aged between 1 and 7 years, each matched to two control children with no history of wheezing. Each participant's home was assessed for moisture damage, condensation, and mold growth by researchers, an independent building assessor and parents. Repeated measures of temperature and humidity were made, and electrostatic dust cloths were used to collect airborne microbes. Cloths were analyzed using qPCR. Children were skin prick tested for aeroallergens to establish atopy. Strong positive associations were found between observations of visible mold and new-onset wheezing in children (adjusted odds ratios ranged between 1.30 and 3.56; P ≤ .05). Visible mold and mold odor were consistently associated with new-onset wheezing in a dose-dependent manner. Measurements of qPCR microbial levels, temperature, and humidity were not associated with new-onset wheezing. The association between mold and new-onset wheeze was not modified by atopic status, suggesting a non-allergic association.

Respiratory symptoms and fractional exhaled nitric oxide (FeNO) among students in Penang, Malaysia in relation to signs of dampness at school and fungal DNA in school dust

Few health studies exist on dampness and mould in schools in the tropics. We studied associations between fraction of exhaled nitric oxide (FeNO), respiratory symptoms and airway infections among students and dampness and fungal DNA in schools in Malaysia. A total of 368 randomly selected students from 32 classrooms in 8 secondary schools in Penang, Malaysia, participated (58% participation rate). Information on current respiratory symptoms and the home environment was collected by a standardised questionnaire. FeNO was measured by NIOX MINO (50ml/min). The classrooms were inspected and dust was collected by vacuuming on special filters and was analysed for five fungal DNA sequences by quantitative PCR. Linear mixed models and 3-level multiple logistic regression (school, classroom, student) were applied adjusting for demographic data and the home environment. Totally 10.3% reported doctor's diagnosed asthma, 15.1% current wheeze, 12.4% current asthma, 37.3% daytime breathlessness, 10.2% nocturnal breathlessness, 38.9% airway infections and 15.5% had pollen or furry pet allergy. The geometric mean of FeNO was 19.9ppb and 45% had elevated FeNO (>20ppb). Boys had higher levels of FeNO. Chinese had less daytime breathlessness than Malay (OR=0.30: p<0.001). Indoor carbon dioxide levels were low (380-720ppm). Dampness was observed in 18% of the classrooms and was associated with respiratory infections (OR=3.70; 95% CI 1.14-12.1) and FeNO (p=0.04). Aspergillus versicolor DNA was detected in 67% of the classrooms. Higher numbers of Aspergillus versicolor DNA in classroom dust were associated with wheeze (p=0.006), current asthma (p=0.002), respiratory infections (p=0.005) and elevated FeNO levels (p=0.02). In conclusion, respiratory symptoms were common among the students and the high FeNO levels indicate ongoing airway inflammation. Building dampness and the mould Aspergillus versicolor in schools in Malaysia can be risk factors for impaired respiratory health among the students.