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Traffic-related Particles Are Associated with Elevated Homocysteine

The VA Normative Aging Study

¹ Department of Environmental Health Sciences, and ² Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, Michigan; ³ VA Normative Aging Study, Veterans Affairs Boston Healthcare System, Boston, Massachusetts; ⁴ School of Medicine, and ⁵ School of Public Health, Boston University, Boston, Massachusetts; ⁶ Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts; and ⁷ Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts

Correspondence and requests for reprints should be addressed to Sung Kyun Park, Sc.D., Department of Environmental Health Sciences, University of Michigan School of Public Health, 109 S. Observatory Street, SPH II-M6240, Ann Arbor, MI 48109. E-mail: sungkyun{at}umich.edu

Rationale: Recent epidemiologic studies have shown that homocysteine, a sulfur-containing amino acid formed during the metabolism of methionine, is a risk factor for atherosclerosis, myocardial infarction, stroke, and thrombosis. Particulate air pollution has been related to cardiovascular death and hospital admission, but the underlying mechanisms are not fully elucidated.

Objectives: We examined the associations between ambient particulate air pollution and plasma concentrations of homocysteine among 960 community-residing older men (mean age, 73.6 ± 6.9 yr).

Methods: Total homocysteine in plasma, measured using high-performance liquid chromatography with fluorescence detection, was regressed on each ambient particulate pollutant (black carbon, organic carbon, sulfate or PM_2.5), and effect modification by plasma and dietary B vitamins (folate, B6, and B12) was examined.

Measurements and Main Results: The median concentration of total homocysteine was 10.6 µmol/L. Statistically significant positive associations of total homocysteine were observed with traffic-related particles (black carbon and organic carbon). No association was observed with sulfate, an indicator of coal combustion particles, or PM_2.5 (particulate matter 2.5 µm in aerodynamic diameter). The effects of black carbon and organic carbon were more pronounced in persons with low concentrations of plasma folate and vitamin B12.

Conclusions: Exposures to ambient particles, particularly from traffic, are associated with elevated plasma total homocysteine. Homocysteine may be a component or biological marker of the oxidation pathways underlying the effect of ambient particles on the cardiovascular system.

Key Words: air pollution • folate • homocysteine • traffic particles • vitamin B12

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Only one epidemiologic study has examined associations between air pollutants and homocysteine, but no experimental study has been conducted. What This Study Adds to the Field Particles generated from traffic vehicles may elevate concentrations of plasma homocysteine. Higher concentrations of plasma folate and vitamin B12 may reduce the adverse effects of particles.