EPA Siloxane Monitoring Proposal September 6 , 2012

The agency has reviewed the proposed environmental monitoring program for certain siloxanes (D4 and D5) as submitted by the Silicones Environmental Health and Safety Council on March 1, 2012 and
related information provided to the agency on August 3, 2012

. T he agency generally agrees with SEHSCs environmental monitoring proposal for direct discharge sites. The agency has determined, particularly with respect to indirect discharge sites and publically owned treatment works, the proposal would not provide adequate information for the agency to conduct a risk assessment. Below is the agency’s position on what would constitute an adequate siloxane environmental monitoring program

.

1. Industrial Sites with Onsite Wastewater Treatment (Direct Discharge Sites )

The Agency agrees with SEHSC that a ll 4 SEHSC member direct discharge sites would be monitored as originally proposed by SEHSC . These sites are SEHSC member sites, most of which are manufacturing
siloxanes and some also process siloxanes and/or formulate products containing siloxanes.

2. Industrial Sites Discharging Wastewater to POTWs ( Indirect Discharge Sites )

These are SEHSC member sites that process siloxanes and formulate products containing siloxanes. The SEHSC proposal did not include monitoring a t these sites. Monitoring data from these sit e s would be used to characterize potential releases of siloxanes from hundreds of processing and formulating sites

, including sites of non

- SEHSC members

.
There are a total of 9 SEHSC indirect discharge sites. EPA believes that of the 9 sites, only five sites
sh ould be monitored because information has been provided to the Agency that indicates that t hree

sites have no releases to water and one site that discharges wastewater to a tertiary treatment site (thes e circumstances must be confirmed by SEHSC)

. T ertiary treatment is not a commonly used
treatment method at POTWs and therefore monitoring at this site is not essential to this effort

.

3. P ublicly Owned Treatment Works (P OTWs )

SEHSC has proposed environmental monitoring at 5 sites. SEHSC’s proposal only includes monitoring of
theoretical worst case siloxane release scenarios versus providing a range of POTWs that would provide a range of release scenarios . The agency has concl uded that 5 sites are insufficient to conduct a risk

assessment because it is too small of a sample to characterize the impact of critical factors (population served by the POTW; treatment method used by the POTW; flow rate of the receiving stream) on rele ases and environmental concentrations of siloxanes f ro m U.S. POTWs

. SEHSC’s proposal to monitor only 5 POTWs using 4 different treatment methods would be considered by many to be anecdotal

. The

a gency’s position is that the number and range of POTWs that would be monitored must be able to account for th e uncertainty and variability of these critical factors. EPA believes that monitoring at 16 carefully selected POTWs could adequately address these critical factors. This would result in data
which coul d be used to characterize a range of POTWs in a risk assessment of desired quality.EPA believes that monitoring developed by this Enforceable Consent Agreement (ECA) should support a

risk assessment that will allow EPA to make a determination on whethe r or not risk management action
is needed to address the release of siloxanes into the environment. Monitoring focused on evaluating a theoretical "worst case" with the implication that additional steps would be required to generate yet
more data if such a worst

- case assessment indicated greater than negligible risk, is not an approach EPA
believes would be efficient and effective for this ECA.

While data from Wang et al. (2010) of D4 and D5 in effluent and sediment from POTWs in Canada is informative, it is likely that the Canadian sites are not representative of US POTWs. The study’s focus on lagoons is not consistent with wastewater treatment in the U.S. I n addition the details of the locations and conditions of monitoring are not available because they are considered confidentia l

. Finally

, biota

was not monitored in this study

. Thus the Canadian data may have limited utility for EPA risk
assessment purposes.

Key factors that are critical in choosing the number and type of POTWs because they lik ely impact the
releases of siloxanes from POTWs are:

Population served by the POTW A POTW that serve s a large population yet has a low influent flow would theoretically result in a worst case (i.e. the greatest mass and highest
concentrations of silox anes are being fed to the POTW). Similarly, a POTW serving a small population but receiving a large influent flow would represent a best case (i.e. smallest mass and lowest concentrations of siloxanes are being fed to the POTW).

Treatment method used in t he POTW A ctivated sludge is the method used treat about 80% of
the volume of waste water across the country. Lagoons are a common treatment method but generally serve smaller communities. There are additional treatment methods used even less frequently which are not a focus of this effort. Flow Rate of the Receiving W ater B ody T he amount of dilution provided by the receiving water body could impact concentrations of siloxanes in water and sediment

.

Additional factors of interest for the monitoring eff ort are:

Org anic Content of the Receiving Water B ody S iloxanes are believed to par tition preferentially
to solids . EPA understands that it would be difficult to identify POTWs for potential monitoring based on this factor, but there would be value in sampling at several POTWs that discharge to a receiving water body with high organic content

. Geography Environmental conditions in different parts of the country could affect the partitioning and sedimentation of siloxanes due to the varying nature of w atersheds and temperature variations can affect partitioning both during and after treatment.The sampling plan matrix shown below is intended to result in a practical and efficient strategy for the

monitoring of a range of possible POTW operations ta king into account the factors noted above

. This sampling proposal calls for monitoring at 12 POTWs and 4 lagoons.

Low Population High Population High POTW Flow Low POTW Flow

Low Dilution Act. Sludge

and Lagoon Act. Sludge Act. Sludge Act. Sludge
and Lagoon

Act. Sludge Act. Sludge Act. Sludge Act. Sludge

Act. Sludge
and Lagoon Act. Sludge Act. Sludge Act. Sludge
and Lagoon High Dilution

High dilution in the above tables means the flow rate of the water body receiving the POTW effluent is much greater than the POTW influent flow rate.

O rganic content of receiving stream should be monitored

. Facilities sampled should be from a variety of locations across the country.

All monitored POTWs should have a low indust rial contribution to influent (<10%). This would allow an understanding of how the use of siloxanes in personal care products (vs. from industrial sources) contributes to their presence in the environment. Also, other sources of industrial

waste water c ould impact a POTW’s ability to treat siloxanes.

Sampling D etails for all Monitored Sites

2 sampling events from each site. Media sampled will include POTW influent, effluent, biosolids, sediment at outfall, surface

water

. For the direct and indirect discharge sites, influent and effluent from on

- site pretreatment and tr eatment system s , if applicable

, would also be monitored. Air sampling at one covered site as proposed by SEHSC. Biota sampling: B enthic and multiple fish species at all SEHSC direct an d indirect discharge sites provided there are sufficient biota present to monitor. EPA believes that monitoring from all these sites is needed to develop a data set for assessment that is better than anecdotal quality. The original SEHSC proposal called for biota monitoring at 4 direct discharge sites and 5 POTWs.