ASHINGTON, Feb. 19 — A new government report concludes that children's health has improved in areas where the government has taken aim at environmental hazards, White House and Environmental Protection Agency officials said today.

On the other hand, the report raises new questions about the need for new areas of study, such as the link between mercury and childhood development and the rising rates of childhood asthma even as air quality has improved over the last 15 years.

The report, the federal government's second comprehensive assessment on children's health that weighs environmental and biological factors, does not have any policy, regulation or financing recommendations, the officials said. But the juxtaposition of the data sets the stage for more environmental studies focused on children, whose medical needs are different from adults'.

The study also sets a benchmark for the government to deal with the hazards of mercury, which scientists have linked to developmental I.Q. deficits and motor skill dysfunction, and which is suspected to play a role in attention deficit disorder and autism. Mercury has been the controversial subject within the environmental regulation arena because power plants release it while burning coal.

The report draws on recently released data on toxins from the Centers for Disease Control and Prevention, which measured the level of mercury in women of child-bearing age. Officials said the report brought together data about the increasing amount of mercury in food and water, but they cautioned that it was too early to draw causal links between the types of diseases that are occurring.

"The number of those fish advisories have been up," said Joe Martyak, a spokesman for the E.P.A., "but it doesn't tell you how many people are getting sick from it."

One of the most important questions raised in the report is about the increasing incidence of asthma, the leading cause of school absenteeism linked to chronic disease. An estimated 3.8 million children have had an asthma attack in the past 12 months, and the direct and indirect costs of asthma are an estimated $14 billion a year.

But rates for asthma have gone up even as outdoor air quality has improved, leading scientists to examine indoor air quality and the effects of immunization.

Officials said the report, which is at the printer and is scheduled to be released soon, also pointed to advances in children's health, many of which have come from targeted government policies. For example, officials reported a decline in children's exposure to second-hand smoke, which is known to cause upper respiratory disorders, asthma and middle ear infections in children.

The report also says that the level of blood lead poisoning in children has dropped significantly in the last 30 years. The Lead Contamination Control Act of 1988 set program efforts to eliminate childhood lead poisoning in the United States. An estimated 300,000 to 400,000 children ages 1 to 5 have alarming levels of lead in their blood, compared with 890,000 in the last study by the disease centers, officials said.

But these cases are the most difficult to eliminate as they occur disproportionately among poor and minority children.

The National Childhood Cancer Foundation reports that each year cancer is diagnosed in 12,500 children and that about 2,300 children and teenagers die from cancer.