Plants
May Help In Widespread Clean-Up of Arsenic Contamination
(Beyond Pesticides, May 13, 2004) A recent study published
in Environmental
Science and Technology shows that a certain species of fern
may be used to rapidly absorb arsenic, a known cancer-causing agent,
from contaminated waters, according to an article in Nature
yesterday. The study, which makes public the preliminary results of
a four-month pilot program, also indicates
the plant’s potential to absorb arsenic from CCA-treated wood.
Authors of the study, Mark Elless of Edenspace Corporation, et. al. found the species of fern, Pteris vittata, is able to absorb the arsenic through a process of phytofiltration. The benefits of the process were assessed based on the amount of arsenic the plants were able absorb and how quickly. The same plants could be used repeatedly with successive batches of tainted water, reports Nature.
The pilot study used 80 hydroponic plants and more than 15,000 gallons of water and reliably demonstrated a reduction in drinking water arsenic levels from greater than 10 parts per billion (ppb) to less than the detection limit of 2 ppb within 24 hours, according to the authors.
Arsenic is a known carcinogen. According to the American Journal of Epidemiology for March 1, 2001, a study conducted by National Taiwan University reported that exposure to arsenic in drinking water at levels of 10.1 ppb to 50 ppb nearly doubled cancer risk compared to the risk in the general population.
In 2001, under the Safe Drinking Water Act, EPA was required to revise the existing standard for arsenic in drinking water from 50 ppb to 10ppb to take effect by January 2006. The World Health Organization also established a Maximum Contaminant Level (MCL) of 10 ppb in drinking water. The change in the standard could affect as many as 4000 community water systems in the U.S. Yet many municipalities are going further and aiming to reduce the arsenic level to 5ppb.
The promising discovery many have far reaching implications particularly since arsenic is ranked by the EPA and the U.S. Agency for Toxic Substances and Disease Registry as the most common and most hazardous substance (based on frequency, toxicity, and human exposure) found at EPA Superfund sites.
“In addition to drinking water,” writes Elless. “The ferns have effectively removed arsenic from a variety of other sources, including chromated copper arsenate (CCA) used in pressure-treated lumber; arsenical pesticides used in apple orchards, citrus groves and grasshopper bait; and arsenical herbicides used in golf courses and cotton fields.”
Arsenic is an occasional highlight in mainstream news largely due to it being a component of chromated copper arsenate (CCA), a wood preserving pesticide widely used in the manufacture of playground equipment. In January 2004 manufacturing of CCA-treated wood for decks and patios, picnic tables, playground equipment, walkways/boardwalks, landscaping timbers, or fencing was banned. CCA-treated wood can still be sold however until supplies are exhausted.
Most other arsenic-removal strategies tend to produce an arsenic-rich chemical sludge, which creates hazardous waste disposal issues. The fern study claims that instead of producing sludge, the sap from the plants is squeezed out in presses removing about three-quarters of the arsenic, reports Nature.
The pilot demonstration culminated more than two years of Edenspace research sponsored by the National Institute of Environmental Health Sciences at the U.S. National Institutes of Health (NIH). The project was carried out by the City of Albuquerque, New Mexico and Edenspace Systems Corporation.
TAKE ACTION: If you are concerned about arsenic levels in your environment or drinking water, contact your local authorities and ask them what levels are currently being measured (in both drinking water and soil and wood tests of playground equipment or other public structures) and how they plan to comply with the new protective standards. For more information on CCA-treated wood, see Beyond Pesticides’ wood program.