1. Toward capturing the exposome variability: Household co-exposure patterns in the LIFE study
Jake Chung
Jan 2016

2. Questions
Is it possible to characterize the density of correlations of environmental exposures?
How are the correlations of exposures driven by shared environment (e.g., within household) vs. the individual?
Aims
1. Explore the co-exposure patterns of chemical biomarkers from 12 classes
2. Examine the influence of familial relatedness in correlation of exposures
Main findings
Comparing females and males:
1. Highly similar co-exposure patterns between the male and female groups
2. Higher within-class Spearman correlations (abs. median r: ) for persistent organic chemicals (PCBs, PBDEs, organochlorine pesticides) than other classes (<0.25)
Comparing couples to above:
1. Both the abs median correlation (abs. median r: < 0.25) and interquartile ranges of correlation (32 to 80% reduction) of all chemical classes are lower

3. Method 1. Load imputed chemical data in R (provided by NICHD)
2. Obtain residuals from regressing chemicals against serum lipids and creatinine
Linear model: scale(log10(biomarker+1)) ~ scale(creatinine) + scale(total lipids)
Total lipid calculated by Philips’ formula
3. Get final Spearman correlation estimates by averaging 10 imputed frame (Rubin’s method)

4. Two generally positively correlated clusters:
1) PCBs, PFCs, organochlorine pesticides, and blood metals
2) phytoestrogens, phthalates, phenols, urinary metals and metalloids, and parabens
Left: females; Right: males
Interactive plots:

5. Similar co-exposure patterns between females and males
(red line represents perfect agreement)

6. Similar density curves between females and males

7. Weaker co-exposure pattern in couples!
Females
Males
Interactive plots:

8. Persistent organic chemicals have higher within-class correlations
Left: females; Right: males

9. Lower within-class correlations in couples
Females
Males

10. Interpretation Co-exposure patterns of biomarkers were found in:
Both between and within chemical classes
With stronger within-class correlation for persistent organic chemicals (PCBs, PBDEs, OCPs)
Implication:
Analytical challenges for exposome-wide association study
p value correction
multicollinearity

11. 2) Damping of correlations in couple group
Chemical correlations were weaker in the couples than females and males
Suggests
People spend over 90% of their time indoor and more than 12 hours a day at home
Couple shares home environment but with weak co-exposure patterns
Non-home environment could be a significant source of exposure variability
Implication
Surrogates such as house dust are commonly used to assess exposures
For life-course, family-based (e.g. fecundity, twin studies), taking only household indoor surrogates for exposure assessment may cause a bias in epidemiological findings.
Could be especially of a concern to persistent organic chemicals with endocrine disrupting capability that shown higher reduction in correlations