Ash from wildfires poses health risk

Disaster News Network: Ash and burned soil from Southern California wildfires in October may pose human health and environmental problems as well as threatening drinking water supplies, according to a preliminary study by the U.S. Geological Survey. The samples, taken from residential areas burned by the Grass Valley and Harris wildfires as well as 26 other sites, can contain "somewhat elevated" levels of metals including arsenic, lead, zinc and copper. "Ash from burned wildlands can also contain caustic alkali materials, though at lower levels than the residential ash," the USGS said. The findings were not unexpected, according to the USGS.

"These findings are consistent with the scientific knowledge about wildfire ash that has led counties in California to issue advisories regarding appropriate precautionary measures to avoid health problems associated with exposure to the ash," said Geoffrey Plumlee, a USGS lead author of the study. Among the precautionary measures suggested were use of appropriate respiratory protection, gloves, long-sleeved shirts and long pants, dust mitigation measures, and washing of skin contacted by the ash. Those measures may be especially important to faith-based and community groups that have been working to clean up burned sites throughout Southern California.

The study also warned of environmental damage from rainfall runoff. "The study results also indicate that rainwater runoff from burned areas may adversely affect ecosystems and the quality of surface drinking water supplies," said Deborah Martin, a USGS wildfire ash specialist and a co-author of the study.

"Given the extent of the burned residential areas, these results suggest that residential portions of burned watersheds may need enhanced cleanup attention before the rains, and possibly enhanced monitoring during the rains," the study said. "Rainwater runoff from the burned residential and wildland areas may also adversely affect water quality and critical species habitat in receiving streams by causing spikes in alkalinity, concentrations of some metals and levels of some nutrients, as has been noted in burned areas elsewhere in the United States."

The study also looked for asbestos in the residential ash. While an initial analysis did not "conclusively" find asbestos, officials said it might still be present in other areas that were not sampled. "The negative finding to date for asbestos does not guarantee that asbestos is absent from the burned residences; it might be present locally in areas of the residences not sampled or analyzed," the study said. ". . . Potentially higher levels of asbestos (and lead) might be expected in burned residential areas with houses constructed earlier than the early 1980s, when use of asbestos and leaded paints in construction materials was common."

The report suggested additional studies be conducted in burned residential areas "to fully examine the potential environmental and health issues associated with residential ash and burned soils."