Workshop of the latest development on the evaluation methodof Environmental Fate & Bioaccumulation

July 1, 2014

The Society of Silicon Chemistry Japan

PROGRAMThe symposium was held on 1st July 2014 in Tokyo under the management of the Silicone
Industry Association of Japan (SIAJ). The program for this event is listed below.

Opening Speech
Keiji Kabeta
Vice Chairman, The Society of Silicon Chemistry, Japan

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4

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5

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9

Weight of Evidence (WoE) for PBT/ POP Assessment
Keith R Solomon
Centre for Toxicology, School of Environmental Sciences, University of Guelph

Current State of the Safety Evaluation of cyclic Volatile Methylsiloxanes(cVMS)- Brief Overview of the Safety Assessments of Cyclics Including
the Avian Study on D5
Kathleen P. Plotzke
Dow Corning Corporation

Volatile Methylsiloxanes in the Water Environment: Method
Development and Application to Environmental Monitoring in Tokyo
Bay Watershed
Yuichi Horii
Center for Environmental Science in Saitama····· 14Long-Range Transport Potential of Volatile Methylsiloxanes
Shihe Xu
Dow Corning Corporation····· 20ENVIRONMENTAL RESOURCES MANAGEMENT

1SILICONE INDUSTRY ASSOCIATION OF JAPANUse of Fugacity Ratio Methodology for Assessment of Bioaccumulation:
Concepts, Applications, and Caveats
Kent B. Woodburn and David E. Powell
Dow Corning Corporation····· 27

Use of Activity and Fugacity in Bioaccumulation and Risk Assessment of
D5
Frank A.P.C. Gobas
School of Resource and Environmental Management, Simon Fraser University····· 32

The fate of cyclic Volatile methylsiloxanes (cVMS) in aquatic
environments: An assessment of spatial distribution, bioaccumulation,
trophic transfer, environmental risk, and long-term trends in Tokyo Bay,Japan
David E. Powell and Kent B. Woodburn
Dow Corning Corporation····· 39ENVIRONMENTAL RESOURCES MANAGEMENT

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SILICONE INDUSTRY ASSOCIATION OF JAPANPreface

ERM has been commissioned by the Silicone Industry Association of Japan (SIAJ) to produce
this report based on the ‘Advanced studies of chemical substance environmental assessment
focusing on cVMS’ workshop hosted by The Society of Silicon Chemistry Japan on 1st July2014.

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SILICONE INDUSTRY ASSOCIATION OF JAPANOpening Speech
Keiji Kabeta
SSCJ Office, Tobita Research Labs., Department of Chemistry, Graduate School of Science, Tohoku
University, Sendai, Japan

About SSCJ
The society was founded in 1996 with the aim of promoting the development of silicone andrelated chemistry. It is led by the chairman, Prof. H. Tobita, of Tohoku University, and there
are currently 450 members with an annual membership fee of JPY 2,000.
SSCJ carries the following four missions:
1. Support growth of young scientists
2. Strengthen cooperation with scientists in Asia and beyond
3. Expand membership and exchange knowledge between relevant fields
4. Enhance silicone chemistry literacy from various fields
In its effort to achieve the above, SSCJ initiates the following activities:• Annual domestic 2-day symposium• Biennial ASIS (Asia Silicone Symposium)• Support to send young scientists to conferences overseas• Annual award-giving to scientists with outstanding achievements

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4SILICONE INDUSTRY ASSOCIATION OF JAPANWeight of Evidence (WoE) for PBT/POP Assessment
Keith R Solomon
Centre for Toxicology, School of Environmental Sciences, University of Guelph, Guelph, Ontario, Canada

Introduction
Chemical assessment of persistent organic pollutants (POPs) and persistent, bioaccumulative,
and toxic (PBT) substances requires good scientific evidence, and quantification (give ascore/weight of evidence) of the strength of the experimental methods and relevance of theobservations can be used to select the best data in the assessment of chemicals with respect toPOPs and PBT properties.
Protection goals and assessment endpoints
The objective of regulations arising from the Stockholm Convention, REACH, and UNECELRT is to protect the health of humans or the environment. However, the protection objectiveof regulations is often general, unquantifiable, and has political origins. Thus, there is a needfor assessment endpoints that are specific, quantifiable, capable of being modeled, andcapable of being tested with scientific hypotheses. Protection from any exposure, to any
chemicals, at any time is impossible, and thus different levels of endpoints are assessed forvarious levels of protection. In human toxicology, endpoints are assessed at level of theindividual in order to achieve high level of protection. In ecotoxicology, endpoints areassessed at a population level in order to achieve protection relating to survival, growth,development, and reproduction. For POPs and PBTs, the assessment endpoints areunacceptable toxic effects in humans or organisms in the environment as a result of a
combination of POP properties that result in exposures that approach or exceed thresholds ofadverse effects. Therefore, the null hypothesis to be tested is “the combination of POP
properties will not result in exposures that approach or exceed thresholds of adverse effect”.
Evidence and lines of evidence for POPs and PBTs
When assessing effects of chemicals on humans or the environment one must assess scientific,
not legal evidence. Epidemiologists Sir Austin Bradford Hill and Sir Richard Doll havedeveloped the Bradford Hill guidelines for causality which assess different factors, including
temporal sequence, specificity, and biological plausibility. A line of evidence must include ata minimum one item of evidence (observation, report, or study). There can be multiple lines
of evidence for one apical endpoint (empirically verifiable outcome of exposure, such as
developmental anomalies or change in breeding behavior).
Lines of evidence can be characterized as follows:
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5SILICONE INDUSTRY ASSOCIATION OF JAPAN1. Convergent lines of evidence - each line of evidence is independent and theprobability of adverse effects is proportional to the sum of the probabilities of the
independent lines of evidence.
2. Concatenated lines of evidence (adverse outcome pathways) – Items of evidence areinternally dependent and the probability of adverse effects is proportional to the
product of the probabilities of the items of evidence. Adverse outcome pathways(AOPs), useful for assessing causality and causation and for extrapolating frombioindicators to apical endpoints, can represent concatenated lines of evidence.
For POPs and PBTs, the risk is proportional to the independent lines of evidence P, B, and T.
Another line of evidence is the long-range transport (LRT), which is used to determine if there
will be effects on apical endpoints in remote regions. However, it must be noted that public
perception and politics can sometimes overrule science. For a given apical endpoint, thecombination of P and B, and sometimes LRT, results in exposures that exceed the thresholdfor T. In the case of concatenated lines of evidence, if a chain is broken (i.e. no TMF, nobioaccumulation) in the line of evidence, the apical endpoint will not be affected. Caution isadvisable due to the fact that (1) aquatic and terrestrial organisms might not show the same
responses, and (2) the properties of the chemical evaluated must be fully characterized to
identify exceptions. The diagram below outlines examples of concatenated lines of evidence
for P and LRT.

Figure 1: Concatenated Lines of Evidence for P and LRT
Weight of evidence (WoE)
In scientific studies, there exists a data paradox. Published studies are often incompletely
documented with insufficient raw data made available. They might not follow standardized
protocols and might be subject to selection bias and publication bias. On the other hand, there
are studies that are conducted under good laboratory practice, quality assurance, and quality
control, where there is no selection or publication bias. Additionally, the existence of a large
amount of data and studies might lead to a disagreement between proponents of each side of ascientific question who will select conclusions from data and studies that support theirposition. This may lead to the use of data that cannot be replicated or that are falsified.
The term “Weight of Evidence” is widely used, most often in a metaphorical sense where
WoE refers to a collection of studies or to an unspecified methodological approach. A better
approach to evaluate studies and obtain WoE is to develop a transparent, theoreticalframework for assessing individual studies as “evidence” of effects or lack of effect. The
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6SILICONE INDUSTRY ASSOCIATION OF JAPANframework should provide a way to evaluate the strength and relevance as well as therelevance of the results of the study.
The process of WoE consists of initial review by one person using a standardized evaluation
sheet, independent quality assurance to ensure that all data and description taken from a paper
were correct, and scoring for expert judgment (SEJ) with a score that was either reduced(internal inconsistency, incorrect comparisons, etc.) or increased (reanalysis of incorrectly
analysed data or concentration response in absence of statistical significance, etc.). In
addition, reduction of search bias, elimination of selection bias, and reduction of thelikelihood of publication bias are necessary when selecting the studies to review. Scores forseveral relevance and strength (toxicity) items are assigned to each study and averaged toprovide a simple rank that is only relative but can be used to summarize weight of evidence.
As seen below, scores can plotted on an X-Y graph for visual presentation.

Strength of the methods and procedures

4

Strong evidenceof no adverse
effects

Strong evidenceof adverse
effects

Weak evidenceof no adverse
effects

Weak evidenceof adverse
effects

3

2

1

0
0

1

2

3

4

Relevance of the response to adverse effects

Figure 2: WoE Visualization PlotIn the visualization graph, the relevance to response to adverse effects or outcomes is plottedon the x-axis, while the scores for strength of the study methods and procedures are plotted
onto the y-axis. Points plotted towards top left, top right, bottom left, and bottom rightindicate strong evidence of no adverse effects, weak evidence of no adverse effects, strong
evidence of adverse effects, and weak evidence of adverse effects, respectively.
Example: Assessing chlorpyrifos as a POP/PBT
A large amount of data are available regarding the pesticide chlorpyrifos. A practical
approach was utilized in order to assess the papers, and unpublished data were also obtained
from Dow AgroSciences. Schemes were developed to assess the strength of the studies on
persistence and bioaccumulation under actual environmental conditions without
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SILICONE INDUSTRY ASSOCIATION OF JAPANnormalization. Extreme conditions were omitted; such as studies conducted at a pH lower than
2. For multiple data points, geometric mean values were utilized. None of the geometricmeans of tested parameters (half-life in water, half-life in soils [laboratory], half-life in soils[field], half-life in sediments, and BCF) triggered the criteria for POP or PBT under EC
1107/2009. In addition, according to Morris et al. 2014 1, no trophic magnification in theplant-caribou-wolf food chain in the Canadian arctic was observed. In summary, chlorpyrifos
is not a POP or a PBT on the basis of P and B. Although chlorpyrifos has been found in semiremote and remote locations (Svalbard and Alaska), concentrations in air, rain and snow,
aquatic and terrestrial media, and biota are small and less than the threshold of toxicity for
terrestrial and aquatic organisms.
Summary
Characterization of POPs and PBTs requires the assessment and characterization of scientificevidence. A number of new regulatory instruments, such as REACH in Europe, refer to WoE
as a method for characterizing the data for making assessments. When using information anddata on chemicals from studies published in the open literature, the quality and relevance inlight of the regulatory endpoints being considered must be assessed as most of the studies are
not conducted in accordance with Good Laboratory Practices (GLP) standards. Specifically,
the strength of the experimental methods and the relevance of the observations need to bequantified and used to select the best data to perform the assessment. With the correct
assessment of data and application of the right scheme, WoE can be applied to lines ofevidence to assess chemicals for POPs and PBT properties.
Questions
1.

If we have a very little information regarding newly developed chemical, can model
prediction be included in the weight of evidence?
Yes, the model prediction can be included in the weight of evidence. However, unless themodel is calibrated well against real data, the relevance of a model may not be as strong as
actual measured values. Chemicals being modeled may be very different from the chemicals
used to calibrate the model. The way to get out of this is to use measured values.

1 Morris AD, Muir DCG, Solomon KR, Teixeira C, Duric M, Wang X.
2014. Bioaccumulation and trophodynamics of current use pesticides andendosulfan in the vegetation-caribou-wolf food chain in the Canadian Arctic. Environmental Toxicology and Chemistry 33:DOI:10.1002/etc.2634.

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8SILICONE INDUSTRY ASSOCIATION OF JAPANCurrent State of the Safety Evaluation of cyclic Volatile
Methylsiloxanes (cVMS) - Brief Overview of the Safety
Assessments of Cyclics Including the Avian Study on D5
Kathleen P. Plotzke
Dow Corning Corporation, Midland, MI, USA

Introduction
Cyclic volatile methyl siloxane (cVMS) are used in the manufacture of larger siloxane
polymers and in a wide range of consumer applications. However, current screening criteria
predict cVMS to have persistent, bioaccumulative, and toxic (PBT) properties. Research on
cVMS’s impacts on humans and the environment has been conducted on these substances todemonstrate their safety.
Global Silicones Council (GSC)
The Global Silicones Council (GSC) is made up of three regional associations comprising the
Silicones Environmental, Health and Safety Council of North America (SEHSC), the Centre
Européen des Silicones (CES), and the Silicone Industry Association of Japan (SIAJ). It
brings together all the major global manufacturers. The objective of the council is to promote
the safe use and stewardship of silicones globally by (1) monitoring the environmental, healthand safety activities of the three Regional Silicones Industry Associations (RSIAs); (2)proactively promoting industry communication with regulatory bodies around the world andwith international environmental, health, and safety organizations; (3) identifying andanticipating opportunities to enhance environmental, health, and safety research relating tosilicones and engaging in global projects to communicate the industry’s product stewardshipcommitment; and (4) sponsoring projects to improve the public’s understanding of thebenefits and safety of silicones.
Cyclic Volatile Methyl Siloxanes (cVMS)
cVMS are clear, low molecular weight liquids with very low water solubility used in the
manufacture of larger siloxane polymers and in a range of consumer applications including
personal care, cleaning agents, and household care. Beneficial physical and chemical
properties including adequate evaporation rate, low surface tension, and no odor are the same
properties that present challenges when evaluating their effects on the environment andhuman health. The chemical structure of the cVMS D4, D5, and D6 is summarized below. As it
can be seen, the number of silicone oxygen bonds increases and water solubility decreases
from D4, to D5, and to D6. The cVMS with lower water solubility is less likely to be found inaqueous environmental compartments.

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9SILICONE INDUSTRY ASSOCIATION OF JAPANFigure 1: Chemical Structure of cVMS
cVMS have robust laboratory and human datasets in support of human health including datafrom standard hazard testing, pharmacokinetics in animals and humans, and physiologicalbased pharmacokinetic models. Human risk assessments recently conducted on cVMS by theEuropean Commission’s Scientific Committee on Consumer Safety, the Cosmetic Ingredient
Review (CIR) Expert Panel, Health Canada, and the UK Environment Agency all conclude
that cVMS do not pose a risk to humans.
Current screening criteria and laboratory bioconcentration studies predict cVMS to have PBTproperties. However, environmental field research indicates that cVMS do not behave asclassic PBTs in the environment and do not biomagnify in aquatic environments. Researchshows that information beyond current screening criteria must be evaluated to understandcVMS behavior in the environment. GSC conducts research under a voluntary productstewardship initiative, of which the key elements are:− emission reduction from point sources− evaluation of emissions from wastewater treatment plants (WWTPs)− steady state modeling− long-term monitoring program− trophic transfer assessments− D5 avian reproductive study.
Voluntary Product Stewardship Initiative
Work on emissions reduction from point sources have involved (1) completion of Chemical
Safety Reports that evaluate potential emissions and fate from industrial and downstream
users applications through models; (2) development of a guidance document on emission
control that was made available to all users of D4 and D5 in manufacturing, processing, andformulation processes; and (3) work with downstream users to jointly identify and facilitate
the widespread use of best practices for waste handling, management, and disposal for D4/D5
at processing and formulation sites.
Because cVMS are used in consumer products, these chemicals end up in municipal WWTPs.
Thus, a project charter has been developed to monitor cVMS in the influent, effluent, andbiosolids from WWTPs in order to collect data to estimate mass loadings of the cVMS
materials to the local environment and to detect any temporal trends associated with the mass
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10SILICONE INDUSTRY ASSOCIATION OF JAPANloading. The proposed areas where WWTPs will be monitored are Oslo (Norway), Tokyo Bay(Japan), Toronto/Hamilton Harbor (Canada), and St. Paul, Minnesota (USA). The feasibility
work, an inter-laboratory comparison of collection/analytical methods of influent/effluent, andanalytical method development for biosolids and influent/effluent have been completed.
Under the modelling initiative, adaptation of the Simple Treat model to handle all types of
WWTPs is complete, and will be validated against monitoring data. In addition, steady statemodeling has been conducted in four different aquatic systems (Oslo fjord, Lake Ontario,
Lake Pepin and Tokyo Bay). According to the result, in all systems, water column
concentrations are predicted to respond rapidly to changes in emissions. However,concentrations in sediment respond more slowly to emission changes. Below is a visualizationof the modeling exercise that was performed at Tokyo Bay during spring time using 15 waterboxes (11 in the surface layer and four in the bottom layer). These models can become very
complex because they require assigning different exposure concentrations to each box
depending on where the WWTPs are located.

Figure 2: Tokyo Bay Modeling
The long-term monitoring program (LTMP) initiative began in 2011for Lake Pepin (USA),
Lake Ontario (Canada), and Oslo fjord (Norway) and in 2012 for Tokyo Bay (Japan).
Locations were selected based on the availability of cVMS monitoring and modeling datafrom previous studies. The objective of LTMP is to determine if concentrations of cVMS
materials in surface sediments and aquatic biota are stable or changing over the project
duration of 5 years. The study is aiming to detect an annual rate of change in concentration of±6% over the course of 5 years and a database has been developed for compiling andanalyzing all data. Sample collection and analysis have been completed for the first 3 years ofdata from Lake Pepin, Lake Ontario, and Oslo Fjord, and for the first 2 years of data from
Tokyo Bay. To date, the sampling program has been successful with no drastic changes to theinitial study design. However, in order to achieve the objective of being able to detect anannual rate of change in concentration of ±6%, replication for some species has been
increased. After 5 years of data collection, the overall trend will be analyzed.
As for the trophic transfer assessment initiative, benthic and pelagic food web monitoring has
been completed at Lake Pepin (Minnesota), Lake Ontario (Canada), Lake Champlain(Vermont), and Tokyo Bay (Japan). The collected data is compared with publicly available
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SILICONE INDUSTRY ASSOCIATION OF JAPANpublications focusing on trophic transfer of cVMS. From the studies it has been determinedthat when calculating trophic magnification factors (TMFs), the exposure concentration
gradient and migration patterns must be considered. When taking these into consideration, theTMFs calculated from the data were less than 1.0 across the sampled food web (trophic
dilution, not trophic magnification). The trophic magnification assessment allows evaluating
if certain substances that might meet the screening criteria biomagnify. In the case of cVMS,
given the data, these substances undergo through dilution, not magnification.
The D5 Japanese Quail Reproduction study initiative was conducted under the OECD 206 test
guideline developed primarily for Bobwhite Quail and Mallard Duck. It consisted of 10 weeks
of exposure in feed prior to egg production and 10 weeks of egg collection. The Japanese
Quail presented challenges in strictly adhering to the test guideline since they are sexuallymature as early as 6 weeks of age and the photoperiod must be adjusted to effectively control
egg production. The OECD 206 recommends that Japanese Quail be “provenbreeders”(Japanese Quail to be able to reproduce) due to high variability in fertility and also
recommends a maximum dose of 1000ppm (i.e., approximately one half of the [acute] LC10
value). A preliminary range-finding study to understand the behavior of D5 at doses of 0, 250,
500, and 1000ppm in diet was conducted. There were no statistically abnormal effects noted
for the endpoints assessed or behavioral abnormalities noted in this 12-week study. The
definitive study was conducted with 18 pairs (1 male, 1 female) per dose group at the start ofthe study. Exposure to D5 began at 24 days of age with doses of 0, 250, 500, and 1000 ppm inthe diet. The parental birds were put in the same cage for 2 weeks and then separated into
adjoining cages for the remainder of the study with 1 visit together allowed per day. The
endpoints listed below were evaluated and, in conclusion, no statistically significant effects
were observed on any parameter measured during the 22-week Japanese Quail reproduction
study.

Figure 3: Statistically Evaluated Endpoints
The No-Observed-Effect Concentration (NOEC) during this study was 1000 mg/kg (1000ppm) of feed (143.5 mg/kg body weight/day) and the Lowest-Observable-EffectConcentration (LOEC) was >1000 mg/kg (1000 ppm) of feed. The NOEC determined in the
study is at a concentration approximately 10,000 times higher than what has been measured in
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12SILICONE INDUSTRY ASSOCIATION OF JAPANsoil, sediment, and fish samples in the environment. The study demonstrates the safety of thematerial found in the environment.
Summary
Current screening criteria and laboratory bioconcentration studies predict cVMS to have PBTproperties. However, environmental field research indicates that cVMS do not behave asclassic PBTs in the environment and do not biomagnify in the aquatic environments. GSC
conducts research under voluntary product stewardship initiative including research on
emission reduction from point sources, evaluation of emissions from wastewater treatment
plants, steady state modeling, long-term monitoring program, trophic transfer assessments,
and a D5 avian reproductive study. Although some of the research studies are still in the datacollection and evaluation phase, the trophic transfer assessment has shown that cVMS goes
through dilution, not magnification through food web, and the Japanese Quail reproduction
study revealed a No-Observed-Effect Concentration (NOEC) that is 10,000 times higher thanwhat has been measured in soil, sediment and fish samples in the environment. The studies
indicate the safety of the material found in the environment.
Questions
1.

If D4, D5, and D6 are volatile and have low solubility, do you have any initiative tomeasure the concentration of these substance in the air?
Yes, there are measurements available and data on how these substances behave in air andother media.
2.

Sioloxanes, has special properties when compared to general organic compound
especially for BCF. However, most of the authorities chose BCF for evaluation. What do
you think about this?
BCF was selected for evaluation of biomagnification. It works for many chemicals but for
substances such as sioloxanes, it does not work as well, as they undergo metabolism.
3. What is the reason for the different lake selection during monitoring programs?
To get a global representation as well as the variety in the region.

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SILICONE INDUSTRY ASSOCIATION OF JAPANVolatile Methylsiloxanes in the Water Environment:
Method Development and Application to Environmental
Monitoring in Tokyo Bay Watershed
Yuichi Horii

Center for Environmental Science, Saitama, Japan

Introduction
The determination of volatile methylsiloxanes (VMS) in the environment is important for theevaluation of human and environmental risks. However, analysis of VMS is very challenging
and information regarding concentration, distribution, and fate of VMS in water environment
is limited. Therefore, a simple method for analysis of cyclic and linear VMS in water andsolid matrices was developed.
Analytical methods for water environment samples (including water, sediment, and fish)
Blank control is the most important factor in cVMS analysis. To reduce contamination, blanklevels of VMS for all product and reagents were tested. Based on these results, lower blankmaterials, such as fluorocarbon materials, were selected to be used for vial seal and inlet
septa.
The analytical procedure for water samples developed during this project has 3 parts:
extraction, elution and quantification. First, the non-filtered water sample is subjected topurge and trap (PT) extraction – this extraction method only allows the extraction of volatile
substances. After PT extraction, the trap sorbent is removed and dried using a stream ofnitrogen. Target chemicals are then eluted with organic solvent, such as dichloromethane(DCM) or hexane, and collected directly in the GC vial for identification and quantification.
The stability test of D5 in water storage at 4°C indicated that relative concentration gradually
decreases with day of storage. 20% of the VMS was lost after 15 days. Thus in this study,
extraction was performed within 4 days after water sampling so that more than 95% of target
chemicals can be recovered.
For analysis of solid matrices, the previous method consisted of directly injecting the sample
to a gas chromatograph/mass spectrometer (GC/MS) after extraction via solvent shaking,without any cleanup steps. For this project, a combination of the solvent shaking extraction
and PT clean-up techniques was used for analysing VMS in solid samples, such as sediments
and fish. The PT extraction technique was applied to remove non-volatile fractions such ascolored components, mineral oils, and lipids. Without this clean-up process, interferences canbe seen in the chromatograms of the GC/MS scan.

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SILICONE INDUSTRY ASSOCIATION OF JAPANFigure 1: Comparison of chromatograms from the GC/MS scanConcentration levels in Tokyo Bay watershed
Two sampling surveys were conducted in the Tokyo Bay watershed to examine the total
concentrations of seven VMS compounds: D3, D4, D5, D6, L3, L4 and L5. Sampling was
first performed between October and November 2012, in nine locations from the main inflow
rivers of Tokyo Bay (including Tsurumi, Tama, Sumida, Ara, Edo and Yoro Rivers). The
second sampling survey was conducted in Saitama in April 2013 at 39 locations from mid to
upstream locations of Ara, Sumida, Naka and Edo Rivers.
The average concentration of the seven VMS compounds for the first round of sampling
conducted in 2012 was 130 ng/L, ranging from 32 to 470 ng/L. The highest concentration was
found near the sewage treatment plants (STPs). Data collected during this sample survey iscomparable to river water data from Germany, France and the UK, in which VMS
concentrations range from 20 to 400 ng/L.
Regarding the data collected in 2013 from mid to upstream river waters, the average
concentration of the seven VMS compounds was 240 ng/L, ranging from approximately 4.9 to1700 ng/L. A positive correlation was found between the concentration of VMS and TOC.
This finding is consistent with the physical and chemical properties of the VMS compounds,
which have high KOC values.

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SILICONE INDUSTRY ASSOCIATION OF JAPANVMS Conc vs. TOC

2000

VMS Conc (ng/L)
1500
y = 95.051x - 99.596
R² = 0.3827

1000
500
0

0

5

10

TOC (mg/L)

15

Figure 2: Correlation between VMS concentration (ng/L) and TOC (mg/L)
The cyclic VMS (cVMS) were present in the water samples collected in Japan at the highest
concentrations, with D5 having the highest concentrations overall, followed by D6 and D4.
Water samples sources included river water, sea water and waste water. Some samples hadvery low concentration of these compounds. Even in the Tokyo Bay, some areas had very low
concentrations that were close to the lower detection limit.
Although there was variation among the samples, significant positive correlations were foundbetween the target chemicals, as shown in the figure below. This suggests that the cVMS
detected in these water samples came from similar sources, such as STPs.

Figure 3: Correlations between the target chemicals
Sources of VMS in the water environment
The usage rate of siloxanes, including cyclic and linear siloxanes, was estimated as 307
mg/capita/day. Among the siloxanes, D5 had the highest rate of 233 mg/capita/day, followedby linear siloxanes, then D6 and D4 (Horii and Kannan, Arch Environ Contam Toxicol, 2008,
55, 701-710).
STPs are suspected to be a major source of VMS. While 90% of VMS is discharged into theair, the remaining 10%enters the WWTP. After the treatment process, 5% of VMS isdischarged to the water environment as effluent. Some of the VMS is discharged into the air
as aeration gas during activated sludge water treatment (Mackay & Cowan-Ellsberry 2011,
SETAC NA).

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SILICONE INDUSTRY ASSOCIATION OF JAPANTo investigate the discharge amount of VMS to the environment as well as the removal
efficiency of VMS in the STP, a mass-balance study was conducted in Saitama, Japan.
Samples of influent, primary effluent, mixed liquor (aeration tank), secondary settling tankwater, final effluent (discharged to the river), dried sludge, and aeration gas (discharged to theatmosphere) were collected from 9 middle to large scale STPs.
The mean concentration of VMS in the influent was found to be 11,000ng/L. This
concentration increased to 51,000ng/L in the mixed liquor in the aeration tank as VMS
absorbs activated sludge. After this process, the concentration of VMS in the secondary
settling tank water dramatically decreased. This indicates that most of the VMS can beremoved by activated sludge treatment.

Figure 4: Concentrations (ng/L) of 7 VMS compounds during the sewage treatment process
On a percentage basis, the composition of influent, primary effluent and mixed liquor was
similar, with D5 having the highest percentage, followed by D6 and D4. In the secondary
settling tank water and final effluent, D3 and D4 increased slightly as D5 was removed in theaeration tank as part of the particulates. Linear VMS compounds had low composition
percentages.
The removal efficiencies of VMS were estimated at two different STPs employing different
processes – the activated sludge treatment process in STP2 and the oxidation ditch process in
STP8.
The VMS removal efficiency at STP2 was 96% (initial loading is 100%). Most of the VMS(95%) was removed by adsorbing with activated sludge. Approximately 20% of the VMS
evaporated with the aeration gas, but almost all of these VMS were removed by the gas filter.
From this STP, 20 kg/year (4.5%) and 0.041 kg/year (0.009%) of VMS is discharged into thewater and air, respectively.

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SILICONE INDUSTRY ASSOCIATION OF JAPANFigure 5: Mass balance of VMS in STP 2 (activated sludge treatment process)
The VMS removal efficiency at STP 8 (oxidation ditch process) was 98%. Most of the VMS(89%) was found to be removed by adsorbing with activated sludge. Since the STP on which
this estimation is based did not have deodorization, evaporated VMS was discharged directly
into the air. Therefore, from this STP, 0.48 kg/year (2.3%) and 8.6 kg/year (42%) of VMS isdischarged into the water and air, respectively.

Figure 6: Mass balance of VMS in STP 8 (oxidation ditch process)
The VMS concentrations in the effluent and the removal efficiencies at the STPs found inJapan are comparable to those found in Canada and European countries (Nordic countries,
Greece, and the UK). The concentration of D6 is relatively high in the UK, which could be
due to the difference in the composition of VMS used in personal care products.
Environmental risk assessment
Using the PNEC values estimated by Environment Canada (D4: 0.2 µg/L, D5: 15 µg/L, andD6: 4.6 µg/L), the hazard quotients (HQ) of cVMS in the water samples were estimated.
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SILICONE INDUSTRY ASSOCIATION OF JAPANHQ≥1: Risk is a concern

HQ<1: Low risk

The average HQ was 0.11, ranging from 0.0026 to 1.1; the highest value was found in the
STP effluent. The samples were mostly composed of D4 (78%), followed by D5 (16%) andD6 (5.8%). This suggests that D4 can be the most important factor for assessing
environmental risk in water.
Questions
1. How was the hazard quotient determined for a mixture?
This was determined by adding the individual hazard quotients of the three compounds
together.
2. Was the half-life data taken from operational data?
This data was obtained from the literature.
In the future, we are planning to measure some metabolites in the water environment.
3. In the risk assessment, STP effluent had a high hazard quotient because it contained alarge amount of D4. What is the source of these waste waters?
The effluent is from municipal waste water.
The effluent did not only contain a large amount of D4, all compounds were present in fairly
high amounts. However, since the PNEC value of D4 is lower than that of other compounds,
its % of the risk is higher than other VMS compounds.
4. Any ideas on improving the detection limit?
One is to increase extraction volume. Now we are using PT extraction so extraction can be
performed on several bottles at once and combined later. This will increase extraction volume
and lower detection limit by increasing water volume.

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SILICONE INDUSTRY ASSOCIATION OF JAPANLongRange Transport Potential of Volatile Methylsiloxanes
Shihe Xu
Dow Corning Corporation, Midland, MI, USA

Introduction
High potential for long-range transport (LRT) is one of the key characteristics of persistentorganic pollutants (POPs) such as PCBs. Volatile methylsiloxanes (VMS) are considered tohave a high LRT. This presentation summarizes the LRT potential (LRTP) of VMS comparedto known POPs.
Definition of long-range transport potential
LRTP is the “potential for long range environmental transport through air, water or migratory
species, with the potential for transfer to a receiving environment in locations distant from thesources of its release” (United Nations Environment Programme [UNEP] 2001 Stockholm
Convention, Annex D). This includes the transport through a medium as well as the transport
or deposition onto surfaces in remote regions of the receiving environment.
Figure 1: Long-range transport via airPOPs are organic substances that have persistent, bioaccumulative and toxic (PBT)-typecharacteristics, are prone to long-range transboundary transport and deposition, and can cause
adverse human health or environmental effects near to and distant from their sources.

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SILICONE INDUSTRY ASSOCIATION OF JAPANBelow are long-range transport metrics:

The upper four transport-oriented metrics focus on the distance a chemical can travel in theenvironment, while the lower three target-oriented metrics focus on the deposition of achemical from the air to a remote surface medium.
The following is the LRTP Screening Criteria in the POP UNEP Stockholm Convention. Bothtarget- and transport-oriented metrics are employed.
1.
2.
3.
4.

Half-life in air > 2 days, orMeasured levels in remote regions that are of potential concern, orMonitoring data showing LRT with potential for transfer to a receiving environment inremote regions, orFate properties and/or model results that demonstrate LRT, with potential for transfer toa receiving environment in remote regions

Most people stop at Criteria 1 without considering deposition when determining LRT anddeposition. This could lead to incorrect conclusions. For example, although the half-lives of
VMS compounds are greater than 2 days, since their air-water partitioning coefficients are 5
or 6 order of magnitudes larger than those of conventional POPs, they do not have thepotential for deposition in remote regions at the concentrations that can cause significant
adverse human health or environmental effects.
Modeling in the global scale using the OECD Tool
The LRTP of cVMS against benchmark chemicals was investigated using the OECD Pov[overall environmental persistence] and LRTP Screening Tool under the uniform and urban
scenarios. For both scenarios, D4, D5, and D6 were found to have (1) characteristic travel
distances (CTD) in km close to or smaller than those of POP reference materials and acetone,
and close to or slightly greater than those of methanol; and (2) transfer efficiency (TE) values(in %) of cVMS much smaller than those of POP references and some HPV chemicals, suchas acetone and methanol. Also, for both metrics, the values were lower under the urban
release scenario, where release rates were proportional to the population density of the urban
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SILICONE INDUSTRY ASSOCIATION OF JAPANcenter. The urban release scenario is a better scenario for cVMS compounds than the uniform
release scenario since most of these compounds are used for personal care products foundmore predominantly in urban areas.
The OECD tool is widely used for its simplicity, and is advantageous because it provides
relative measures of LRTP, and considers chemical distributions for persistence estimation.
However, the tool is limited in that it is not based on realistic emission scenarios. The tool
calculates three values based on the assumption that 100% of the chemical is released to theair, water and/or soil, and selects the highest value out of the three. Thus, values are only valid
in relative terms and can only be compared to benchmark compounds.
Latitudinal distribution of VMS modelled by GloboPOP
There are two points regarding the basic emission scenario for VMS. First, the majority of
VMS is released from three zones from the northern hemisphere: N-temporal, N-subtropicaland N-tropical. Second, approximately 95% of VMS is released into the air (based on D5
from: Xu and Wania. 2013. Chemosphere 93, 835-843).
The mass of D4 and D5 remaining in the air as a ratio of the yearly release rates wascalculated using the GloboPOP model. PCB28, the lower boundary for POPs, andhexachlorobenzene (HCB) were selected as reference chemicals. This modelling investigation
illustrated the fact that a fraction of D4 and D5 can reach the Arctic atmosphere, but not theAntarctic atmosphere.
Similarly, the distribution of the above four compounds on surface media as a ratio of theiryearly release rates was compared. The surface media deposition rates for PCB28 and HCB
were five orders of magnitude greater than those for D4 and D5. Thus, although a fraction of
VMS can reach the Arctic atmosphere, very little can actually deposit to the Arctic surface
media.
Spatial distribution patterns of contaminants measured in spring-summer months
The figure below shows the spatial distribution patterns of D4, D5 and αhexachlorocyclohexane (HCH). The concentration at the source (urban region) was set as 1,
and the concentrations at the rural regions, to which the compounds get transported, werenormalized to the source concentrations.

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SILICONE INDUSTRY ASSOCIATION OF JAPANFigure 2: Spatial distribution patterns of D4, D5 and α-HCH
Figure 2 implies that individuals with inhalation issues of α-HCH at the source region will
most likely experience the same issue in remote regions since the concentrations of thecompound only decrease slightly. On the other hand, concentrations decrease dramaticallyfrom the source to remote regions for D4 and D5. Therefore, there will be unlikely any
significant inhalation exposure of VMS like D4 and D5 for human in the remote regions.
For environmental exposure, deposition from remote atmosphere to surface media is essential.
For α-HCH, environmental exposure is high since its concentration in soil is five orders ofmagnitude higher than that in air, consistent with its soil to air partitioning coefficient.
Air-to-soil deposition in remote regions
Air-to-soil deposition is the most important mechanism for environmental exposure of VMS
in remote regions. Given a model environment in which air in the troposphere (6,000 km) is inequilibrium with the soil (depth = 20 cm; ρs = 1.3 g cm-3; foc = 2%), the ratio between themass distribution of soil (MS) and air (MA) can be calculated using the following equation,
valid at any temperature:
MS/MA = ρsfoc(Vs/VA)(KOC/KAW)
At 25°C, this equation can be reduced to the following:log KAW = -6.06 + log KOC– log (MS/MA)
By plotting the log KOC and log KAW of the compounds, the deposition of the compounds tosoil can be derived. For all “Old” and New” POPs, 50% to ~100% (e.g. PFOS) of thecompound will partitione into the soil under the conditions evaluated, suggesting significant
environmental exposure will be resulted once the compounds reach the remote atmosphere.
For D4 and D5, this deposition will be less than 1%. This difference is due to the partitioning
coefficients of the chemicals.

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SILICONE INDUSTRY ASSOCIATION OF JAPANThe table below shows the percentage of distribution for D4, D5 and D6 at several
temperatures and at two depths, 5 cm and 25 cm. The percentage of distribution was
calculated by dividing the mass in soil by the total mass in the soil and air compartments in
the remote region.
Table 1: Effect of temperature on air-to-soil deposition

The table indicates that soil partitioning is low for D4, D5 and D6 even at lower temperatures.
Comparison of model results and environmental monitoring data
Environmental monitoring of D5 in air during spring/summer months revealed that a small
fraction of airborne D5 can reach the Arctic atmosphere.
The minimum and maximum concentrations of D5 were plotted to determine theconcentration of the compound that can actually partition to the soil, based on equilibrium
partitioning coefficients under different temperatures. Concentrations of D5 above the MDL
were measured and determined to be much higher than predicted by the deposition
concentration. Deposition from air contributes negligibly to the mass in remote soil. D5 flows
from soil to air, since its fugacity in soil is high.
Similar data were obtained for D4, although concentrations were 10 times lower than for D5.
Much fewer measurements were obtained from the soil since concentrations were low. The
estimated deposition from air for both D4 and D5 could not be detected using current
methods.
Sediment-to-air partitioning is also important. The figure below shows the mass fraction ofcVMS in % distributed in sediments at two different temperatures, 0 and 20°C.

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SILICONE INDUSTRY ASSOCIATION OF JAPANFigure 3: Sediment-to-air partioning of cVMS compounds
Other than D6, all compounds have mass fraction values of less than 1 from the point source
to the remote region.
As for monitored data for cVMS compounds in sediments, estimated deposition
concentrations for D4 were several orders of magnitudes lower than the no observed effectconcentration (NOEC) concentrations (Midge, Blackworm). Similar results were found for
D5, although D5 measured concentrations had a wider range. D5 had higher concentrations in
sediments because more D5 is used in personal care products.
Summary
A small fraction of the released VMS can reach the remote atmosphere via air. However, thepotential of the airborne VMS to deposit on surfaces from the air is negligible. Detectableamounts of VMS in remote regions could be attributed to local sources and not necessarily to
long-range transport. Finally, VMS compounds are not expected to do any harm to humans
and the environment in the far-field, or remote regions.
In conclusion, for a compound, a half-life in air > 2 days does not necessarily indicate longrange transboundary transport and deposition. A combination of partitioning properties is also
important to assess if a chemical is likely to cause significant adverse human health andenvironmental effects near to and distant from their sources. Based on this robust scientificassessment, VMS should not be considered as POPs.
Questions
1. What about partitioning of compounds to rain droplets or snow?
Partitioning to rain droplets is low due to high KAW values.
Partitioning to snow is not significant. You have a certain amount of compound on the snow
surface. When the snow melts, compounds do not stay in the water, rather, they partition into
the air.

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SILICONE INDUSTRY ASSOCIATION OF JAPAN2. Can the method employed in this study be used for regulatory or screening purposes?
The analysis is not approved for regulatory purposes, yet in my observation, the only special
method used in this study is the urban center emission scenario. The conclusions should be thesame without this scenario.

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SILICONE INDUSTRY ASSOCIATION OF JAPANUse of Fugacity Ratio Methodology for Assessment of
Bioaccumulation: Concepts, Applications, and Caveats
Kent B. Woodburn and David E. Powell
Dow Corning Corporation, Midland, MI, USA

Introduction
Participants in a 2009 Society for Environmental Toxicology and Chemistry (SETAC)
Pellston Conference concluded that the fugacity ratio approach is a practical framework for
decision making in chemical management and regulation, particularly with regard to an
overall assessment of bioaccumulation potential, providing a more formal method to test the
hypothesis of whether biomagnification occurs. This presentation summarizes the reasons forthat conclusion.
Review – Bioaccumulation (‘B’)
Bioaccumulation is studied in order to determine if a substance accumulates or biomagnifies
sufficiently to potentially cause significant adverse effects in individual organisms andpopulations and, ultimately, affect ecosystems. An example is the accumulation of DDT
metabolite in food webs in USA during the 1960s. The accumulation affected the thickness ofbird egg shell, causing significant adverse effects on its population. As famously quoted by
Paracelsus (1493 – 1541), the father of toxicology, “Dose makes the poison.” We set limits on
bioaccumulation to avoid impact on toxicity, and such a limit is often referred to as “Critical
Body Burden,” or “CBB.” ‘B’ is often identified by regulators as a bioconcentration factor(BCF) of >2000 (B) to >5000(vB).
The followings are different ‘B’ metrics used to measure bioaccumulation. However,regulators often work with single criteria, the BCF, due to its familiarity.
 Bioconcentration Factor (BCF): biota/water Bioaccumulatio Factor (BAF): biota/water + food Biota-Sediment Accumulation Factor (BSAF): biota/sediment Biomagnification Factor (BMF): biota/food Trophic Magnification Factor (TMF): biota/food web
As outlined below, the best indicator of bioaccumulation is measurements in the field.

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SILICONE INDUSTRY ASSOCIATION OF JAPANFigure 1: Evaluation Metrics of Bioaccumulation
What is fugacity (f)?
Fugacity is often viewed as “chemical activity”, “chemical potential”, or “escaping tendency”.
In the gas phase, fugacity may be considered as partial pressure (i.e. the pressure of the gas
generated in equilibrium with a pure liquid at the same temperature). The definition of
fugacity is the ratio of the chemical’s concentration in media ‘m’ (Cm) to the media’s fugacity
capacity (Zm).
f = Cm/ Zm
Fugacity capacity (Zm) is the capacity of a phase to solubilize and absorb a chemical, and it
depends on the phase composition, temperature, pressure, and the physical-chemical
properties of the chemical. Fugacity capacity can be calculated based on the media and thecompound properties.
What are fugacity ratios (F)?
Chemical equilibrium is present when fugacity in biota is equal to fugacity in reference
media. In this case the fugacity ratio (F) is equal to 1. In the case of fugacity ratio between
biota and water, the fugacity ratio is BCF that is adjusted for the lipid content and normalized
for its Kow value as outlined below.
Fbiota/water = BCF * dbiota * Zwater / Zbiota
or, more simply
Fbiota/water = BCF * dbiota / Φlipid / Kow
where Kow is a surrogate for lipid/water partitioning behaviour.
Similarly, Fbiota-sediment value is the BSAF adjusted for Koc/Kow ratio.
Fbiota/sediment = BSAFOC/lipid * dlipid * Koc/Kow
However, for many lipophilic chemicals (PCBs, polycyclic aromatic hydrocarbons [PAHs],etc.), Koc ≅ Kow, and Fbiota/sediment becomes
Fbiota/sediment ≅ BSAFOC/lipid
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SILICONE INDUSTRY ASSOCIATION OF JAPANIn the case of some materials including cyclic and linear siloxanes where Koc values are far
lower than Kow values, adjustments of the BSAF value must be made accordingly, using theratio of Koc/Kow.
How do fugacity ratios (‘F’) help us view ‘B’ metrics?
A fugacity ratio greater than 1 indicates that the chemical in the organism has achieved ahigher activity than the exposure medium (i.e., the chemical potential in the organism has
been magnified). Fugacity ratio of less than 1 can occur when the chemical potential in thebiota is less than in the medium to which it is exposed. This occurs if the chemical is quickly
biotransformed in the organism or is poorly transferred (as is the case for sioloxanes) in a foodweb, and indicates biodilution.
TMF is more or less a pure fugacity ratio as we’re looking at lipid to lipid transfer. Other
measurements including BCF and BSAF can be converted into fugacity ratios. Once
converted, the metrics can be plotted into a single graph to evaluate the level ofbioaccumulation. The fugacity ratios of “B” metrics for PCB 153 indicate biomagnification as
all the fugacity ratios are greater than 1.
1000

PCB 153: F >1, biomagnifying

Line: Median (50%)
Box range: 10% to 90%

Fugacity Ratio

100

10

Source: Burkhard et al. (2012)
IEAM 8:17-31

1

Ratio = 1
0.1

0.01

s
s
h
F
F
F
F
F
F
BC r BA d BM brate h BA y BM brate nt-fis d TMleet e f oo
e
t er
is
t
te
e
r
f
i
r
r
a
a
m
p
i
F
e
e
ld
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/w ish/
v
v
/w
h/
-in
ish
Fie ld fis nt-in ta/seishb F SAF
bf
bf
e
La
La
La
Fie dim ld bio
B
b
e
s
La
Fie
t a/
bio
ld
e
i
F

Figure 2: Fugacity Ratios and PCB 153
On the other hand, the fugacity ratios of “B” metrics for Pyrene, which has an intermediate
Kow (log Kow ~5) with a moderate metabolism rate and field TMF value of less than 1,
indicate biodilution, as can be seen in the plot below.

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SILICONE INDUSTRY ASSOCIATION OF JAPANFugacity Ratio: PCB 153 versus Pyrene
Fugacity Ratio (fbiota / fmatrix)

103

PCB 153: F >1, biomagnifying
102

101

100

10-1

10-2

Source: Burkhard et al. (2012)
IEAM 8:17-31

10-3

10-4

Pyrene: F <1, not biomagnifying

s
s
h
F
F
F
F
F
F
BC r BA d BM brate h BA y BM brate nt-fis d TMet e f oo
e
t er
is
te
te
el
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f
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a
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F
e
e
/
/
d
w
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/
v
v
/w
h
ish
-in
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Fie ld fis nt-in ta/seishb F SAF
bf
bf
e
La
La
La
Fie dim ld bio
B
b
e
s
La
Fie
t a/
bio
ld
e
i
F

Figure 3: Fugacity Ratios and Pyrene
Caveats
Biota fugacity capacity (Zbiota) assumes that lipids are the dominant phase for storinghydrophobic organic chemicals and that octanol and lipid have equivalent storage capabilities.
This assumption may have effects on BCF, BAF, and BSAF metrics where water or organiccarbon is the reference matrix. For some compounds it is a good assumption that you can havelipid to water partitioning value that is equivalent to the Kow value. As seen in the relationshipof Klw/Kow and lipid content of D5 (shown below), when there is low fraction membrane lipids(high amount of storage lipids), the agreement between Kow and lipid water partitioning isquite good. As fraction membrane lipids increase, the value of the partitioning value drops
down and results in a 50-fold difference.

*Seston et al. 2014. IEAM 10: 142-144.

Figure 4: Relationship of Klw/Kow and Lipid Content for D5
Summary
Recent literature supports using fugacity ratio methodology to identify biomagnifying
substances. “B” metrics are expressed on a common basis and test a single hypothesis.
Although laboratory ‘B’ metrics (e.g., BCF) have been perceived as problematic indicators ofbiomagnification, the use of fugacity ratios may revive their utility., For instance, although the
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SILICONE INDUSTRY ASSOCIATION OF JAPANtraditional BCF may exceed 5000 L/kg, low assimilation, metabolism, etc., can produce a
non-biomagnifying substance (TMF<1). In addition, the use of fugacity ratios provides aweight-of-evidence graphical approach that increases confidence in the “B” assessment.
Questions1.

The importance of each ‘B’ metric is different. Use of fugacity gives each metric a same
weight. Can you comment on this?
Field metric, such as the TMF is the best indicator. However, the fugacity ratio allows us to
use laboratory metric in a much more effective fashion than previously. Certain parameterssuch as BCF can theoretically never produce a fugacity ratio that is greater than 1. Thus, it isimportant to look at values such as TMF as well.
2.

BCF is often used in a regulatory context. What is the real world application of fugacity
ratio?
TMF is only useful for chemicals that are currently in commerce. The use of fugacity ratio
will be useful for newly developed materials. BCF does not work for all chemicals including
D5 and in these cases fugacity ratio will be useful. The Stockholm criteria of 5000 L/kg is
only a screening tool, and not a final indicator.

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SILICONE INDUSTRY ASSOCIATION OF JAPANUse of Activity and Fugacity in Bioaccumulation andRisk Assessment of D5
Frank A.P.C. Gobas
School of Resource and Environmental Management, Simon Fraser University, British Columbia, Canada

Introduction
The evaluators of chemicals need to make better use of existing data (“increasing lines ofevidence”) and to consider the quantity and quality of data (“weight of evidence”). This
presentation discusses the application of the thermodynamic quantities of activity and fugacity
to improve bioaccumulation and risk assessments of commercial chemicals.
Decamethylcyclopentasiloxane (D5)
D5 is a good example to show the challenges faced in bioaccumulation and risk assessment. It
is also a chemical which has gone through a full regulatory review in Canada, and many of thefindings either have been or will be published in scientific literature. D5 is present in many
consumer products including suntan lotion, cosmetics, and so on, and some of theformulations contain as much as 50% D5. Some of the properties of D5 include low watersolubility (0.00001 mol*m-3), high log Kow (8.03), high log Koc (5.17), high vapor pressure(33.2 Pa), and high Henry’s constant (3.34*106 Pa*m3*mol-1).
Evaluation of D5 in Canada
D5 is on the domestic substance list in Canada was evaluated by Health Canada for humanhealth and Environment Canada for environmental health. The evaluation consisted of threephases. The first phase is evaluation of persistence, bioaccumulation, and inherent toxicity.
After the first phase, a screening level risk assessment is conducted, where exposure data iscompared to toxicity to assess risk. If the substance turns out to be problematic, it is placed ona list of toxic substances and is then subject to possible regulatory control. Thus, in Canada,risk is evaluated rather than persistency (P), bioaccumulation (B), and toxicity (T).

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SILICONE INDUSTRY ASSOCIATION OF JAPANFigure 1: Domestic Substance List Procedure
Section 64 of the Canadian Environmental Protection Act (CEPA) 1999 defines a substanceas “toxic” if it is entering or may enter the environment in a quantity or concentration or underconditionsA) Having or that may have an immediate or long-term harmful effect on theenvironment;B) Constituting or that may constitute a danger to the environment on which humanlife depends;
C) Constituting or that may constitute a danger in Canada to human life or health.
Canadian Environmental Protection Act
In 2009, Health Canada reported in the Canada Gazette that “D5 does not pose a danger in
Canada to human life or health,” while Environmental Canada reported that “D5 has or may
have an immediate or long-term harmful effect on the environment.” This is interesting
because some consumer products contain a high concentration of D5 and according to thestatement by Health Canada this does not pose dangerous effects. However, according to thestatement by Environment Canada, when D5 reaches the environment (even at low
concentrations) via consumer products, it has or may have harmful effects. In 2012, withmostly the same amount of data, Environment Canada reported in Canada Gazette that “D5will not pose a danger to the environment”. In addition the Siloxane D5 Board of Review(2011) indicated “Future uses of D5 will not pose a danger to the environment”. The total
reversal of the decision while the data available did not change illustrates challenges
encountered in evaluating this substance.
Activity and Fugacity in evaluation of bioaccumulation and risk assessment
When a substance is evaluated, there is quite an amount of data available including lab
studies, models, genomics, field studies, metabolomics, in vivo studies, and in vitro studies.
Parameters evaluated include LC50, NOAEC, and EC50 for toxicity tests, and information iscollected for a number of media such as air, water, soil, sediment, and fish. Due to thecomplex nature of the evaluation approach, several challenges are faced, including

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SILICONE INDUSTRY ASSOCIATION OF JAPAN

comparability, consistency, error and variability. In many cases, very little of the original data
is used in the decision making process.
The concept of fugacity and activity has been around for a while and has initially beendeveloped by Gilbert N. Lewis (1875 – 1946). The approach proved to be very helpful inmedicine, and J. Ferguson, H. Meyer, and E. Overton applied the concept to better understandanesthetics. Don Mackay reintroduced the concept into environmental chemistry andtoxicology in 1981. Fugacity and activity help to take into account all the data available andallow them to be integrated appropriately. The fugacity approach is better and easier to apply
for chemicals that go into the gas phase such as D5. On the other hand, activity is a better
approach for substances that dissolve in water instead of going into the gas phase. Fugacity is
the partial pressure a chemical exerts over any surface, and it normalizes the concentration toa property called fugacity capacity that measures how well a phase can accommodate achemical. Every chemical has a fugacity minimum value of 0 and a maximum value equal toits vapor pressure; it is thermodynamically impossible for a chemical to have a fugacity greate
than its vapour pressure. Activity is defined as the concentration of a chemical divided by its
solubility limit. The same concept can be applied to solid phases such as soil, sediment or
biological organisms. Values of activity range from a minimum of 0 to a maximum of 1
(solubility capacity).
As energy moves from objects with high temperature to objects with low temperature, thechemical moves from high fugacity to low fugacity. Thus, when chemicals are released into
the environment, they often dilute. However, there are chemicals that go from low fugacity tohigh fugacity through the food chain, resulting in biomagnification or ecologicalmagnification. The limitations of the fugacity or the activity approach are the following:A) Solubilities must be known. Some models of methods to estimate solubilities
include SPARC, ChemiSilico, EpiSuite, and solvatochromic predictions.
B) Modifying factors include temperature, ionic strength, and pH.
C) Biotransformation must be considered.
D) Biomagnification must be considered.
Application of fugacity approach to D5
The fugacity approach was applied to D5, as the vapor pressure is high (33.2 Pa) and welldefined. In bioaccumulation assessment, fugacity is applied to different organisms and media
and can be calculated using parameters that include the bioconcentration factor (BCF), thebiota-sediment accumulation factor (BSAF), and the biomagnification factor (BMF0. A
fugacity ratio of 1 indicates thermodynamic equilibrium; less than 1 indicatesbiotransformation, growth dilution, and/or rapid excretion; and greater than 1 indicatesbiomagnification.
Below is a graph plotting the BCF values of D5 and PCB52 measured on a wet weight basis
during different studies of fish. It can be seen that there is variability in the BCF fromdifferent studies for D5. In addition, all the BCF values for D5 are lower than that of PCB52
indicating lower bioaccumulation. However, looking at BSAF, the data indicate that D5 has
higher bioaccumulation than PCB52 for lumbriculus variegatus.

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SILICONE INDUSTRY ASSOCIATION OF JAPANFigure 2: BCF of and BSAF of D5 and of PCB52
When these data are translated into fugacity ratios, the contradiction of data is eliminated as
can be seen in the graph below resulting in consistency and comparability. Research indicatesthat fugacity ratios of less than 1 are due to metabolism.

Figure 3: BCF and BSAF of D5 and of PCB52 translated into fugacity ratios
Risk Assessment – D5
In risk assessment, exposure data must be compared to toxicity data. Below is a graph plotting
fugacity of D5 in different environmental media that illustrated the variability of fugacity indifferent environmental media, as evidenced by the large order of magnitude plotted. The redline indicates the vapor pressure, the maximum value of fugacity. Values below the red line
are possible, while those above the red line are impossible. The exposure data and toxicity
values, which are normally reported in different units, are translated into fugacity ratios forcomparability. The blue line, indicating the no observed effects concentration (NOEC), is the
toxicity data from different studies dealing with exposure to water. The brown line, also
indicating the NOEC, is the toxicity data from different studies dealing with exposure to
sediments. However, since the blue and brown lines are both above the red line (vapor
pressure), we know these values are not feasible in the environment. This is due to the factthat in the studies, animals are exposed to concentration levels above the solubility limit.
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SILICONE INDUSTRY ASSOCIATION OF JAPANThus, the blue and brown lines are valid only in a situation where pure chemical is available
in the system.

Figure 4: Fugacity of D5 in Various Environmental Media
Risk Assessment – Di(2-ethylhexyl)phthalate (DEHP)
DEHP has low water solubility (0.00000637 mol*m-3), high log Kow (7.73), high log Koa(10.53), and relatively low Henry’s Law constant (3.95 Pa*m3*mol-1). Due to its ability tobiotransform, both the original compound and the metabolite must be taken into account. The
evaluation is further complicated by the fact that the metabolite can dissociate. Whenassessing risk, we must look at how the data overlaps with the toxicological data (in vitro
effects, NOECs, and LOAELs). In this case, in vitro effects were compared to internalfugacities while NOECs and LOAELs were compared to external fugacities. The results of the
fugacity and activity assessments are shown below.

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SILICONE INDUSTRY ASSOCIATION OF JAPANFigure 5: Fugacity and Activity Assessment of DEHP and its Metabolite

Summary
The current method for evaluation of chemicals includes the characterization of environmental
properties such as P, B, and T. These evaluation methods give rise to many challenges
including the lack of data or of the “right” data, conflicting data, variability and error in thedata, the presence of different types of data, data consistency in space and more. Activity andfugacity data can contribute to bioaccumulation and risk assessment by increasing the numberof data used in the analysis, improving comparisons between observations in different media,
removing apparent inconsistencies, screening out possibly erroneous data, including in vitro
toxicity and passive sampling data, and providing a possible framework for assessing
cumulative risks for multiple chemicals.

Questions1.

The fact that fugacity of D5 of wastewater was greater than 1, is that an indication thatthe material in present as a solid or a liquid, or is it absorbed into organic matter and theanalysis is incorrectly done?
The data point was investigated and there was a release of liquid D5. The data for thewastewater treatment plants were taken from D5 production plants.
2. Do you have any recommendation for running a test model for new chemicals?
The regulators are very constrained by acts and laws. However, good, sound information cansupersede what the law states. As a scientist, we recommend to have a sound rationale and go
beyond the minimum regulatory requirements when needed.
3.

Different test results can be compared with fugacity. How many tests are needed to havea confident fugacity assessment?
You must use the available data to the best of your ability.

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SILICONE INDUSTRY ASSOCIATION OF JAPAN4.

For the PCB graph, I see a lot of data are out of range. Based on your experience, is thisa usual phenomenon?
We have seen it for D5 and DEHP. Chemicals with high Kow are very hard to evaluate
properly and pose challenges to toxicologists and risk assessors.

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SILICONE INDUSTRY ASSOCIATION OF JAPANThe fate of cyclic volatile methylsiloxanes (cVMS) in aquatic
environments: An assessment of spatial distribution,
bioaccumulation, trophic transfer, environmental risk, andlong-term trends in Tokyo Bay, Japan.
David E. Powell and Kent B. Woodburn
Dow Corning Corporation, Midland, MI, USA

Introduction
cVMS are widely used in industrial and consumer applications. Wastewater represents major
post-use disposal route and the effluents are the foremost source of cVMS to aquatic
environments. Japan (Silicone Industry Association of Japan), Europe (Centre Européen desSilicones [European Center for Silicones]), and North America (Silicones Environmental,
Health, and Safety Center) have initiated global monitoring programs that include aquatic
environments impacted by municipal wastewater effluents. This presentation focuses on dataacquired in Tokyo Bay, Japan.
Study area
The inner Tokyo Bay area was divided into 20 different sections, covering an area of 500 km2.
The top 1-centimeter of sediment surfaces were collected at each of those sections.

Figure 1: Inner Tokyo Bay study area
Spatial distribution of compounds
In 2011, targeted sampling of dominant species led to the collection of eight different fish
species, while in 2012 and 2013, five different fish species were collected.

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SILICONE INDUSTRY ASSOCIATION OF JAPANThe home range, or the feeding area for a specific species, is determined by the ecology andsize of species. In other words, large organisms will have large feeding areas and thereby
large home ranges and vice versa for small organisms. This is particularly important for
cVMS compounds since they are discharged from a point-source and thus have varying
concentration gradients.
The dry weight sediment concentrations of D4, D5 and D6 were analysed in the Tokyo Bay
sample sediments collected from 2011 to 2013. The concentration of D5 was the highest,
followed by D4 and D6. Spatial distributions were similar for D5 and D6, and more localized
for D4. Each compound had a wide concentration range, with a 10-fold or greater difference
between the lowest and highest concentrations.
Bioaccumulation and trophic transfer
The food web sampled in 2011 included eight different fish species, ranging from the dotted
gizzard shad to the Japanese sea bass. The species were pelagic, demersal, or benthopelagicorganisms. Sediment and benthic invertebrate samples were also collected.
Food webs are normally characterized by a stable isotope of Nitrogen (15N) or Carbon (13C).
In this study, trophic levels were assigned based on the 15N signatures of the different species.
For each different fish species, 15N values were measured by applying the generic enrichment
factor of 3.4‰.
The best technique for evaluating the biomagnification of compounds is by using Trophic
Magnification Factors (TMFs). The table below shows four techniques used to calculate
TMFs.
Table 1: Methods for calculating TMFs

Other than the standard, bootstrap and benchmark methods, this study employed an exposurecorrected benchmark technique, a combination of the benchmark and exposure correction
techniques. The benchmark technique differs from the linear and bootstrap regression
techniques in that it employs a 15N enrichment factor derived from a benchmark compound, in
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SILICONE INDUSTRY ASSOCIATION OF JAPANthis case the polychlorinated biphenyl PCB-180. An average TMF of 4.0 is used as abenchmark to obtain the 15N enrichment value for a particular food web, based on the
behavior of PCB-180. On the other hand, the exposure correction technique is useful forcompounds like cVMS that vary in concentration due to their discharge characteristics. Since
concentrations in organisms may differ due to this pattern of discharge, rather than strictly
using concentrations found in organisms, concentrations are normalized to sedimentconcentrations, as most cVMS are found in the sediment. Thus, biota-sediment accumulation
factors (BSAFs) are used in place of compound concentrations found in organisms.
Below are the Δ15NEF and slope values from the benchmarking analysis of the Tokyo Bay
food web.

With the standard technique, the TMF (PCB-180) was 2.8, which is lower than what is
anticipated for this compound. With the benchmark and benchmark correction techniques, theTMF values increased to the expected value of 4.0. Agreement between the model and data
was approximately 70% for the benchmark correction technique.
The results from the Tokyo Bay food web, including the TMF values for D4, D5 and D6, areshown in the table below.
Table 2: Results from the Tokyo Bay food web

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SILICONE INDUSTRY ASSOCIATION OF JAPANTMF values obtained for D4, D5 and D6 were slightly less than 1.0 for all methods. While theR-squared values for the standard, bootstrap and benchmark techniques were fairly poor, theR-square value increased (particularly for D5) with the benchmark correction technique.
Overall, the results show that the TMF for cVMS compounds considered in this study wasless than 1, which is consistent with what has been observed in similar food webs.
Environmental risk
A risk assessment was performed for sediment-dwelling organisms. The risk quotient (RQ)
was calculated by dividing the 95th percentile concentration of the compound by the 5th
percentile no observed effect concentration (NOEC) of benthic invertebrates. The RQ values
for D4, D5 and D6 were far less than 1, as shown below.
cVMS compound
D4
D5
D6

Risk quotient
0.006
0.014
0.0003Long-term trends in the concentrations of cVMS
An increase in water content especially over the last year, a regular decrease in TOC and an
abrupt decrease in density has been observed in the composition of Tokyo Bay sediments
between 2011 to 2013. These observations reflect random sampling bias across aheterogeneous study area, rather than temporal trends. Sampling bias may be propagated into
biased and skewed concentrations. Volumetric concentrations (ng/cm3) and total burden (kg)should minimize bias compared to mass-based concentrations (ng/g dw, ng/g ww or ng/gOC), which can be skewed by water content and organic carbon sources.
The dry mass concentrations of D4, D5 and D6 increased nominally over 2011 to 2013,
however no significant change was observed in terms of the total burden of chemicals in theecosystem. As for fish collected from 2011 to 2013, no significant trend was observed acrossvarious organisms for all cVMS compounds, including D4, D5 and D6.
SummarycVMS compounds are log-normally distributed across surface sediments. Greatest
concentrations were found in sediments near the point of discharge (municipal wastewater
treatment plants) and concentrations decreased with increasing distance from the point source.
In terms of bioaccumulation and trophic transfer, ecology and migration patterns of theorganisms should be considered, rather than assuming uniform exposure and distribution.
TMF was less than 1.0 across the sampled food web, indicating trophic dilution instead oftrophic magnification. Trophic dilution has also been observed in similar samples of theecosystem, including those from Lake Erie. Risk ratios for invertebrates were less than orequal to 0.01, indicating very low risk associated with cVMS in Tokyo Bay. Regarding longterm trends, there was considerable between-year variation in concentrations, specifically in
sediments but also in fish. There were no apparent decreasing or increasing trends observed.
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SILICONE INDUSTRY ASSOCIATION OF JAPANThus, the results to date collectively indicate cVMS in Tokyo Bay are unlikely to represent a
present or future environmental concern.
Questions
1. Will redox potentials affect sediment concentrations?
Anoxic conditions were not observed in most of the sampled ecosystems. This might explainsome of the differences in the number of species collected over the years.
2. Were sediment cores sectioned to determine the distribution of chemicals by depth? How
can changes in the distribution be explained?
No attempts were made at sectioning sediment cores.
One suggestion for the differences observed in sediment distributions over the years is theinfluence of the tsunami that hit Japan on March 11th, 2011. Other possible explanations
include impacts from typhoons or dredging activities within Tokyo Bay.
3. Are there any differences in the monitored data compared with other countries such as the
U.S or Europe?
Previous studies were based on ecosystems in benthal pelagic environments. The Tokyo Bay
food web examined in 2011 was composed of pelagic organisms. Results from this pelagic
food web seem to be consistent with the trophic dilution of cVMS materials in benthal pelagic
food webs.

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SILICONE INDUSTRY ASSOCIATION OF JAPANThis summary was preparedby
ERM Japan
andSilicone Industry Association of Japanin commission of
The Society of Silicon Chemistry Japan