As part of a multiple-tier research program, interactions of the herbicide Vision (glyphosate) with two stressors, pH and food level, were examined. Effects of the formulated product Vision were tested at two test concentrations (0.75 and 1.50 mg acid equivalent/L), two pH levels (pH 5.5 and 7.5), and under high and low food concentrations. Effects of each stressor alone and in combination were examined using two common wetland taxa: Zooplankton, Simocephalus vetulus, and tadpoles (Gosner stage 25) of Rana pipiens. For S. vetulus, survival, reproduction, and development time were measured; survival was measured for R. pipiens. For both species, significant effects of the herbicide were measured at concentrations lower than the calculated worst-case value for the expected environmental concentration ([EEC], 1.40 mg acid equivalent/L). Moreover, high pH (7.5) increased the toxic effects of the herbicide on all response variables for both species even though it improved reproductive rate of S. vetulus over pH 5.5 in the absence of herbicide. Stress due to low food alone also interacted with pH 5.5 to diminish S. vetulus survival. These results support the general postulate that multiple stress interactions may exacerbate chemical effects on aquatic biota in natural systems.

The authors used data from the Black Women's Health Study to assess the association between neighborhood urban form and physical activity. Women reported hours/week of utilitarian and exercise walking and of vigorous activity in 1995 and on biennial follow-up questionnaires through 2001. Housing density, road networks, availability of public transit, sidewalks, and parks were characterized for the residential neighborhoods of 20,354 Black Women's Health Study participants living in New York, New York; Chicago, Illinois; and Los Angeles, California. The authors quantified the associations between features of the environment and physical activity using odds ratios for >or=5 relative to <5 hours/week of physical activity. For all women, housing density had the strongest association with utilitarian walking (odds ratio for the most- compared with the least-dense quintile = 2.72, 95% confidence interval: 2.22, 3.31), followed by availability of public transit. Women who moved during follow-up to neighborhoods of lower density were 36% more likely to decrease their levels of utilitarian walking, and those who moved to neighborhoods of higher density were 23% more likely to increase their levels of utilitarian walking, relative to women who moved to neighborhoods of similar density. These data suggest that increases in housing density may lead to increases in utilitarian walking among African-American women.

Background-Numerous cross-sectional studies have found higher levels of obesity among residents of auto-oriented, sprawling areas compared to residents of more urban areas.

Interactions of herbicides and natural environmental stressors such as pH and food availability are poorly understood. We tested a chemical formulation of triclopyr (Release) at environmentally relevant test concentrations (0.25 and 0.50 mg L(-1)) in combination with two levels of pH (pH 5.5 and 7.5), and two levels of food availability (high and low). Population level effects of each stressor alone and in combination with the others were investigated using Simocephalus vetulus, a zooplankton species, and Rana pipiens tadpoles (Gosner stage 25), both common to forest ponds and wetlands. Herbicide treatments resulted in significant decreases in survival of both test species as well as reproduction and development time for S. vetulus at levels 5-10x below predicted worst case environmental concentrations (2.6 mg L(-1)). This laboratory study demonstrates a probable risk of toxic effects of Release herbicide which may be significantly increased by low food availability and by low pH at environmentally relevant concentrations.