NEW YORK (Reuters Health) – Very low blood lead levels — well below the 10 mcg/dL threshold for deleterious effects set by the U.S. Centers for Disease Control — can adversely affect how a child’s cardiovascular system responds to acute stress, according to a study presented at the American Physiological Society annual meeting, part of the Experimental Biology 2009 conference held this week in New Orleans.

In the study, Dr. James A. MacKenzie of the State University of New York at Oswego and colleagues had 140 children, aged 9 to 11 years, complete a psychologically stressful computer task. They measured the children’s cardiovascular function, including total peripheral resistance, while at rest and while they performed the stressful task.

Blood lead levels in the children were no higher than 3.76 mcg/dL. Higher blood lead levels, the team found, were significantly associated with increased total peripheral resistance responses to acute stress, as well as diminished stroke volume and cardiac output responses to acute stress.

“This vascular pattern of response to acute stress tasks may predict future hypertension,” the investigators note in a meeting abstract.

In addition, serum levels of aldosterone were negatively associated with blood lead levels and positively associated with sympathetic nervous system reactivity to acute stress.

“We believe lead causes an increase in sympathetic nervous activity during rest which reduces the body’s ability to generate a response when stress comes along,” Dr. MacKenzie said in a prepared statement.

“What’s interesting,” he noted in an interview with Reuters Health, “is that the levels of lead were all very low in the children who participated.” However, he cautioned that “these are still preliminary studies; the work is ongoing, but we are seeing very interesting findings.”