Association of antenatal and early childhood air pollution and greenspace exposures with respiratory pathogen upper airway acquisitions and respiratory health outcomes

Figures & data

Figure 1. Flow chart of nasal swabs and symptom diaries from children in the Observational Research in childhood infectious diseases study.

Table 1. Characteristics of the observational research in the childhood infectious diseases (ORChID) cohort (N = 158).

Characteristic	N (%)
Gender (Male)	75 (47.5)
Season of birth
Summer (December to February)	42 (26.6)
Autumn (March to May)	30 (19.0)
Winter (June to August)	43 (27.2)
Spring (September to November)	43 (27.2)
Vaginal delivery	107 (67.7)
Gestational age at birth^a
36–38-weeks	36 (22.8)
39–41-weeks	122 (77.2)
Family history
Either parent has asthma/eczema	80 (50.6)
Household smoke exposure at birth (N = 156)
Yes	19 (12.2)
Older child(ren) in house at birth	55 (34.8)
Maternal education status (N = 157)
University degree	99 (63.1)
Diploma/certificate	38 (24.2)
Secondary school	20 (12.7)
Mode of feeding (N = 150)
Exclusive breastfeeding until at least age 3-months	101 (67.3)
Pneumococcal conjugate vaccine doses^b
6-weeks (N = 149)	145 (97.2)
4-months (N = 144)	141 (96.5)
6-months (N = 141)	137 (93.8)
Childcare attendance^c
At 3-months (N = 142)	4 (2.8)
At 6-months (N = 133)	31 (23.3)
At 12-months (N = 116)	72 (62.1)
At 18-months (N = 108)	92 (85.2)
At 24-months (N = 103)	86 (83.5)

^aTwo participants were born between 36.0 and 36.6-weeks gestation.

^bAt the time of the ORChID study, pneumococcal conjugate vaccines in Australia were administered as a 3-dose primary course without a booster dose in the 2nd year of life.

^cChildcare attendance included both care from a regulated childcare service and non-regulated care by relatives or friends.

Table 2. Association between air pollution and greenspace at birth, and the number of weeks with respiratory pathogen detections in the first 3-months-of-life (158 children; 1,717 swabs).

	Weeks detected		Unadjusted^b (N = 158)		Adjusted^c (N = 155)
Outcome	Mean (SD)	Exposure^a	MD (95%CI)	P-value	MD (95%CI)	P-value
Rhinovirus	0.94 (1.43)
		NO2	0.00 (−0.16, 0.16)	0.97	−0.21 (−0.49, 0.07)	0.14
		PM2.5	0.04 (−0.20, 0.27)	0.77	0.28 (−0.08, 0.66)	0.13
		NDVI	−0.21 (−0.46, 0.05)	0.11	−0.28 (−0.59; 0.02)	0.07
Any virus	1.50 (2.26)
		NO2	−0.02 (−0.32, 0.27)	0.88	−0.30 (−0.75, 0.16)	0.20
		PM2.5	0.07 (−0.38, 0.51)	0.77	0.37 (−0.28, 1.02)	0.26
		NDVI	−0.33 (−0.68; 0.02)	0.06	-0.45 (−0.88, −0.02)	0.04
Streptococcus pneumoniae	1.30 (2.02)
		NO2	−0.07 (−0.41, 0.26)	0.67	0.07 (−0.41, 0.54)	0.78
		PM2.5	−0.25 (−0.65, 0.15)	0.22	−0.37 (−0.91, 0.19)	0.19
		NDVI	−0.08 (−0.43, 0.28)	0.67	−0.08 (−0.45, 0.29)	0.68
Moraxella catarrhalis	1.20 (2.61)
		NO2	−0.02 (−0.39, 0.34)	0.89	−0.08 (−0.54, 0.39)	0.74
		PM2.5	0.09 (−0.50, 0.70)	0.74	0.06 (−0.68, 0.79)	0.88
		NDVI	-0.48 (−0.88, −0.08)	0.002	-0.50 (−0.93, −0.08)	0.02
Hemophilus influenzae	0.25 (0.92)
		NO2	0.01 (−0.15, 0.18)	0.88	0.09 (−0.16, 0.33)	0.48
		PM2.5	0.00 (−0.14, 0.14)	0.97	−0.08 (−0.30, 0.14)	0.48
		NDVI	0.03 (−0.13, 0.19)	0.68	0.07 (−0.06, 0.21)	0.29

Abbreviations: CI: Confidence Interval; MD: Mean Difference; NDVI: Normalised difference vegetation index NO₂: nitrogen dioxide; PM_2.5: fine particulate matter <2.5 µm in aerodynamic diameter; SD: standard deviation.

Results are presented as MD (95%CI) per interquartile range increase.

^aExposure estimated as time-fixed for the full antenatal period.

^bOne participant missing data for each of PM_2.5 and NDVI exposures.

^cAdjusted for all environmental factors, season of birth, and maternal education (a proxy for socioeconomic status; one participant missing from maternal education data).

Table 3. Association between air pollution and greenspace, and time-to-first respiratory pathogen and to first symptomatic respiratory virus detections in the first 2-years-of-life (158 children; 11126 swabs).

		Median (25^th−75^th percentile)	Unadjusted (N = 158)		Adjusted^b (N = 157)
Outcome	Exposure^a	survival time (days)	HR (95%CI)	P-value	HR (95%CI)	P-value
First rhinovirus detection		94 (52–155)
	NO2		1.06 (0.76, 1.48)	0.73	1.04 (0.67, 1.60)	0.87
	PM2.5		1.05 (0.75, 1.47)	0.78	1.02 (0.65, 1.61)	0.92
	NDVI		0.89 (0.61, 1.28)	0.53	0.93 (0.63, 1.37)	0.70
First symptomatic rhinovirus detection		210 (129–331)
	NO2		1.15 (0.74, 1.81)	0.52	0.85 (0.51, 1.43)	0.55
	PM2.5		1.34 (0.87, 2.05)	0.18	1.75 (1.04, 2.97)	0.04
	NDVI		1.06 (0.70, 1.59)	0.76	1.35 (0.87, 2.10)	0.18
First any respiratory virus detections		86 (39–135)
	NO2		1.08 (0.76, 1.52)	0.68	1.03 (0.66, 1.61)	0.88
	PM2.5		0.99 (0.69, 1.40)	0.94	0.97 (0.61, 1.54)	0.91
	NDVI		0.96 (0.66, 1.40)	0.83	0.99 (0.66, 1.47)	0.95
First any symptomatic respiratory virus detections		188 (117–259)
	NO2		1.11 (0.71, 1.74)	0.65	0.91 (0.52, 1.59)	0.75
	PM2.5		1.15 (0.77, 1.73)	0.49	1.32 (0.79, 2.19)	0.29
	NDVI		1.07 (0.67, 1.71)	0.76	1.16 (0.70, 1.91)	0.56
First Streptococcus pneumoniae detection		97 (26–215)
	NO2		0.91 (0.67, 1.23)	0.54	0.74 (0.50, 1.09)	0.13
	PM2.5		1.12 (0.83, 1.51)	0.47	1.34 (0.93, 1.92)	0.11
	NDVI		0.91 (0.65, 1.26)	0.57	0.89 (0.63, 1.25)	0.49
First Moraxella catarrhalis detection		176 (86–284)
	NO2		1.05 (0.75, 1.48)	0.77	1.04 (0.67, 1.61)	0.87
	PM2.5		1.06 (0.76, 1.49)	0.73	1.06 (0.68, 1.64)	0.80
	NDVI		0.71 (0.47, 1.07)	0.10	0.71 (0.47, 1.08)	0.11
First Hemophilus influenzae detections		346 (202–551)
	NO2		1.97 (1.29, 3.00)	0.002	1.96 (1.22, 3.16)	0.006
	PM2.5		1.36 (0.96, 1.91)	0.08	1.02 (0.64, 1.62)	0.95
	NDVI		0.98 (0.65, 1.49)	0.93	1.07 (0.65, 1.75)	0.79

Abbreviations: CI: confidence interval; HR: hazard ratio; NDVI: Normalised difference vegetation index; NO₂: nitrogen dioxide; ORChID; Observational Research in Childhood Infectious Diseases; PM_2.5: fine particulate matter ≤2.5 µm in aerodynamic diameter.

HRs calculated using Cox proportional hazards regression. HR represents the change per interquartile range increase in the environmental factor.

^aExposure estimated as time-varying for the first 2-years-of-life. ^bAdjusted regression models include all three environmental factors and season of birth and mother’s highest education status (a proxy for socioeconomic status) as covariables. One participant missing from maternal education data.

Table 4. Air pollution and greenspace exposure and risk of wheezing (ever) in the first 2-years-of-life (N = 154 participants and 87,547 diary-days) and asthma outcomes at ages 5–7-years (N = 84 participants).

		Raw		Standardised		Unadjusted Model^b N = 154		Adjusted Model^b,c N = 154
Outcome	Exposures^a	Never wheeze N = 99	Wheeze N = 55	Never wheeze N = 99	Wheeze N = 55
		Median (IQR)^d	Median (IQR)^d	Median (IQR)^d	Median (IQR)^d	IRR (95%CI)	P-value	IRR (95%CI)	P-value
Wheeze	NO2	7.04 (2.11)	7.20 (2.67)	0.02 (0.94)	0.09 (1.2)	1.08 (0.87, 1.34)	0.48	0.94 (0.71, 1.24)	0.65
	PM2.5	6.64 (0.96)	6.65 (1.14)	0.10 (0.86)	0.11 (1.02)	1.11 (0.86, 1.42)	0.42	1.14 (0.82, 1.58)	0.43
	NDVI	0.47 (0.08)	0.44 (0.08)	0.19 (0.83)	−0.07 (0.65)	0.77 (0.58, 1.01)	0.06	0.75 (0.56, 1.00)	0.05
		No asthma N = 55	Asthma N = 29	No asthma N = 55	Asthma N = 29	OR (95%CI) N = 84	P-value	OR (95%CI) N = 84	P-value
Asthma	NO2	7.28 (1.91)	7.33 (3.08)	0.13 (0.86)	0.15 (1.38)	1.05 (0.06, 18.43)	0.98	1.16 (0.03, 45.56)	0.94
	PM2.5	6.66 (0.87)	6.67 (1.06)	0.12 (0.78)	0.12 (0.96)	0.98 (0.05, 18.78)	0.99	0.94 (0.02, 53.45)	0.97
	NDVI	0.46 (0.09)	0.45 (0.07)	0.10 (0.98)	−0.05 (0.81)	1.14 (0.04, 32.68)	0.94	1.20 (0.03, 46.17)	0.92

Abbreviations: CI: confidence interval; IQR: interquartile range; IRR: incident rate ratio; NO₂: nitrogen dioxide; NDVI: Normalised difference vegetation index; OR: odds ratio; PM_2.5: fine particulate matter ≤2.5 µm in aerodynamic diameter.

Wheeze measured using mixed-effects Poisson regression and reported as IRR. Asthma measured using mixed-effects logistic regression and reported as OR. Child included as a random effect in all models. Standardised values were used for analyses and results are presented per IQR increase.

^aExposure estimated as time-varying for the first 2-years of life.

^b4 children did not return diary after enrolment.

^cAdjusted model includes three main effects (NO₂, PM_2.5, and NDVI) and season of birth as covariables for wheeze outcome and maternal education status for asthma outcome. One participant missing from maternal education data.

^dIQR is represented as the 75^th percentile minus the 25^th percentile.

Data availability statement

De-identified participant data, the data dictionary, and related documents (e.g. case report forms) will be made available on written request to the senior author. Requests must be accompanied by a formal protocol for the use of the data and approval from the relevant Human Research Ethics Committees. A written and signed data access agreement will be required.