WSDOT Herbicide Use
Herbicides are efficient and effective tools for vegetation management
and weed control. However, WSDOT recognizes there may be potential impacts to
health and the environment, and minimizes herbicide use wherever possible.
WSDOT
uses herbicides two ways:
- to maintain a vegetation-free strip at the edge of the pavement where necessary
- to selectively control and eliminate undesirable plants
Historically, about 60 percent of the herbicides used by the agency
were for annual maintenance of a vegetation-free strip at the edge of
pavement. WSDOT is currently studying alternatives to this practice to
determine the most appropriate and cost effective methods for varying
roadsides around the state.
For herbicides used to control weeds and other unwanted plants,
WSDOT follows a process that helps ensure herbicides are used appropriately
and only when necessary in combination with other effective control measures.
The ultimate goal in any treatment is to replace unwanted vegetation
with
appropriate native plants. In many cases herbicides are an effective
tool for initial control of a problem. When combined with other control
measures,
herbicide use can be minimized or eliminated over time.
WSDOT has been tracking its herbicide use trends in detail since 2002. Herbicide
use is reported annually by pounds of active ingredient applied. This information
is available to the public. To obtain a copy please email willarr@wsdot.wa.gov.
Minimizing Risk from Herbicide Use
Two important factors in herbicide selection and application are potential risks to human health and the environment. It is WSDOT policy that any herbicide used on state highway right of way be screened through a scientific risk assessment specific to application rates and methods used by the agency. If certain herbicides are found to have a potential for higher toxicity to human health or the environment, their use on state highway roadsides may be limited, phased out, or immediately eliminated.
In 1993, WSDOT completed a toxicological analysis and risk assessment for herbicides used in the roadside vegetation management program. In 2003 and 2005 a consultant updated the information for the agency based on current WSDOT use and any new scientific findings. This updated analysis now considers all herbicides and applications methods currenlty employed by the agency.
Analysis of risk was based on very conservative assumptions of any potential exposures from WSDOT roadside applications. Findings from these assessments indicate that for most herbicides in most situations, WSDOT’s use of herbicides pose a low to very low potential risk to human and environmental health. In cases where the potential risks were calculated to be above low, WSDOT has placed limitations on use to further minimize potential for exposure. The table Herbicides Approved for use on WSDOT Rights of Way outlines WSDOT use for individual herbicide including precautions and restrictions were they apply. Fact sheets summarizing the toxicology and potential risks for the individual herbicides used by WSDOT can be viewed by clicking on the chemical names below.
Full documentation of WSDOT Herbicide use analysis and risk assessment is also available: 1993 - Roadside Vegetation Management EIS, Appendix B.
Introduction - 2003/2005 Supplement to the 1993 Vegetation Management EIS, Appendix B
Chapter 1- Herbicide Active Ingredient Properties
Chapter 2 - Wildlife Risk Assessment
Chapter 3 - Aquatic Risk Assessment
Chapter 4 - Human Health Risk Assessment
Chapter 5 - Toxicological Data Summaries
WSDOT Policy for Approval and Use of Any New Herbicide Products
Any new herbicides or formulations of existing herbicides that become
available and have potential for use in roadside vegetation management
will be screened, evaluated and approved based on the following procedures:
All new pesticide products that may be used for roadside vegetation
management by the Washington State Department of Transportation will
be formally evaluated for environmental and human health impacts prior
to addition to the statewide contract and use on WSDOT rights of way. No pesticide products
will be used on WSDOT right-of-way without approval through the process
as described below.
Submit request for review/evaluation to the Headquarters Maintenance Office.
If warranted, an internal evaluation will be conducted by the
Headquarters Maintenance Office to determine if a formal risk assessment
is needed.
If a formal risk assessment is determined necessary, the product
will be referred to an independent consultant for analysis and report
on potential risk associated with the product.
The Headquarters Maintenance Office will review the formal risk assessment
and a determination regarding use will be made. If the product is approved
for use, the product will be added to the state contract. If the product
poses unacceptable risk it will not be included on the contract and the
results of findings will be documented.
|
