The Office of Pesticide Programs’ Monitoring for Atrazine 

in Community Water Systems

Status Update - August 2009

Atrazine Drinking Water Monitoring Data

Currently, an intensive monitoring program to look for atrazine residues
in drinking water from approximately 150 community water systems (CWS)
is ongoing. These systems, located primarily in the Midwest, are among
the most vulnerable to atrazine exposure. 

Through its review of these data, the Agency has confirmed that none of
the systems have exceeded OPP's level of concern, a 90-day average of
37.5 parts per billion (ppb) of atrazine and its degradates.  In fact,
the Agency has released 20 CWS from the program because these systems
have had no exceedences of EPA’s level of concern after five years of
monitoring.  EPA has added approximately 20 CWS into the program based
on data gathered under the Safe Drinking Water Act (SDWA).

The data available are the following:

A summary of data submitted by the registrant from 2003 – 2007.

The complete raw data from the program from 2003-2008.

 

Both the summary and complete raw data are available in two locations:

OPP’s public docket for atrazine located at docket number
EPA-HQ-OPP-2003-0367 on www.regulations.gov, and 

On OPP’s Atrazine Updates Web page at
http://www.epa.gov/pesticides/reregistration/atrazine/atrazine_update.ht
m

The raw data, contained in 7 spreadsheets, present atrazine drinking
water monitoring data that are required under the Agency’s 2003
Atrazine Reregistration Eligibility Decision (RED) and subsequent
Memorandum of Agreement (MOA) with the atrazine registrants.  These
Atrazine Monitoring Program (AMP) data files contain the results of the
required sampling, by year, for all CWS that have been monitored over a
6-year period from 2003-2008.  

Each data file includes a “ReadMe” worksheet that explains the data
contained in the file.  AMP data for 2003 and 2004 do not contain
simazine data.  AMP data from the latter half of 2005 onward contain
data for all triazine residues, including simazine.  

If you need these data in a different format than the Excel™
spreadsheets for accessibility or other reasons, please contact the
Chemical Review Manager listed on the Agency’s atrazine website at
http://www.epa.gov/pesticides/reregistration/atrazine/index.htm.

Interpreting the Atrazine Drinking Water Monitoring Data

An EPA level of concern is specific to a particular issue (human health,
for example) and an exposure period.  For example, a long-term (or
chronic) level of exposure would be associated with an exposure over
many months or years, whereas an intermediate level of exposure would be
looking at potential health effects over a three-month period.  Through
the atrazine monitoring programs in place, EPA can evaluate all these
potential exposures.

Atrazine potential risk and how it is evaluated

Change in hormone levels is the most sensitive health effect observed in
an extensive battery of atrazine toxicity tests.  In other words, if the
Agency’s standard is protective of hormonal effects, it will protect
against all other effects that occur at higher levels.  The Agency’s
risk assessment supporting the re-registration of atrazine incorporates
standard safety factors to ensure protection of public health, as well
as an additional safety factor to ensure further protection for
children.  

As a result, EPA’s risk assessment includes a 300-fold margin of
safety to help ensure that an exposure will not affect hormone levels,
and a 1000-fold margin of safety to help protect against long-term or
chronic effects.  In other words, the exposure that the Agency allows
under is at least 300 to 1000 times more protective than the level where
the Agency saw no adverse effects in the most sensitive animal species
tested.  EPA applies these additional safety factors as a precaution to
protect the public health of all consumers in the United States.

The risk assessment is based on the best and most current science
available.  Based on this risk analysis the Agency determined that
concentrations of atrazine and its metabolites in raw water below an
average of 37.5 ppb over a 90-day period ensures protection of pregnant
women and all others, and concentrations of atrazine in finished water
that do not exceed 3 ppb as an annual average protect consumers from
longer term chronic effects. 

The following paragraphs describe the short-, intermediate-, and
long-term exposure levels that EPA has evaluated and found to be
protective of human health.

Short-term exposure--Within these data, you may see individual spikes of
atrazine concentrations of 59 parts per billion (ppb) or higher.  Based
on the Agency’s screening-level assessment conducted for the Atrazine
Interim Reregistration Eligibility Decision (IRED), one-day
concentrations less than the Drinking Water Level of Concern (DWLOC) of
298 ppb do not exceed the Agency’s level of concern for acute effects.
 In other words, occasional readings of atrazine that are below 298 ppb
in water treated by municipalities do not pose a risk to human health.

Intermediate-term exposure--The Office of Pesticide Programs’ level of
concern for drinking water is an intermediate level of exposure where
the level is exceeded if, in a 90-day rolling average, the concentration
exceeds 37.5 ppb for atrazine and its degradates in raw water.  After
six years of monitoring, although some amount of atrazine may be
detected in community water systems, none of the 150 CWS in the
monitoring program have exceeded the 37.5 ppb level of concern as a
90-day rolling average in raw water.  This suggests that the
restrictions and use practices required by the Agency in 2003 are
working to reduce the amount of atrazine reaching water bodies, thereby
protecting public health.  If any CWS were to exceed this level twice
within a five-year period, EPA would prohibit atrazine use in the
watershed associated with the CWS.  

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