Quantifying traffic exposure.

Living near traffic adversely affects health outcomes. Traffic exposure metrics include distance to high-traffic roads, traffic volume on nearby roads, traffic within buffer distances, measured pollutant concentrations, land-use regression estimates of pollution concentrations, and others. We used Geographic Information System software to explore a new approach using traffic count data and a kernel density calculation to generate a traffic density surface with a resolution of 50 m. The density value in each cell reflects all the traffic on all the roads within the distance specified in the kernel density algorithm. The effect of a given roadway on the raster cell value depends on the amount of traffic on the road segment, its distance from the raster cell, and the form of the algorithm. We used a Gaussian algorithm in which traffic influence became insignificant beyond 300 m. This metric integrates the deleterious effects of traffic rather than focusing on one pollutant. The density surface can be used to impute exposure at any point, and it can be used to quantify integrated exposure along a global positioning system route. The traffic density calculation compares favorably with other metrics for assessing traffic exposure and can be used in a variety of applications.

Relationship between markers of inflammation and anaemia in children of Papua New Guinea.

OBJECTIVE: To assess the association of the acute-phase protein biomarkers, C-reactive protein (CRP) and α1-acid glycoprotein (AGP), with anaemia in children aged 6-59·9 months in Papua New Guinea. DESIGN: A nationally representative household-based cross-sectional survey of children aged 6-59·9 months was used to assess the relationships between various combinations of elevated CRP (>5 mg/l) and AGP (>1·2 g/l) with anaemia. Logistic regression was used to determine if other factors, such as age, sex, measures of anthropometry, region, urban/rural residence and household size, modified or confounded the acute-phase protein-anaemia association. SETTING: Papua New Guinea. SUBJECTS: A total of 870 children aged 6-59·9 months from the 2005 Papua New Guinea National Micronutrient Survey were assessed. RESULTS: The following prevalence estimates were found: anaemia 48 %; elevated CRP 32 %; and elevated AGP 33 %. Children with elevated CRP had a prevalence of anaemia of 66 % compared with children with normal CRP who had a prevalence of 40 %. Corresponding estimates for AGP were 61 % and 42 %, respectively. Similar results were found with combinations of elevated CRP and AGP. The higher prevalence of anaemia in children with elevated CRP and/or AGP was still present after controlling for confounders. CONCLUSIONS: Elevated levels of CRP and AGP were significantly associated with a higher prevalence of anaemia in the children surveyed. There are no expert group recommendations on whether to or how to account for markers of inflammation in presenting results on anaemia prevalence. Additional research would be helpful to clarify this issue.