Volatile methyl siloxanes Carrier in antiperspirants/deodorants Shampoo, conditioners, cosmetics VC exempt cleaning solvents Estimated global emissions to the atmosphere of >30000 tonnes/yr not including industrial use for silicone polymer (PDMS) production Mammalian toxicology relatively well studied D4 is a possible EDC Relatively limited environmental measurements D4 D5 D6
Examples of siloxanes-based chemicals identified as potentially persistent and bioaccumulative in Howard and Muir (ES&T 2010) Structural group Substances CAS # or common name Log Kow BC using BCWIN Atmos oxidation half-life (days) Prod n in 2006 TSCA IUR (USA, M lbs) Cyclics D4 6.8 12880 8.9 100-500 M Cyclics D5 8.0 4160 7.2 22-45 M Linears L4, MD2M 8.2 3390 7.2 1-10 M Structure H 3 C H 3 C H C 3 H 3 C H 3 C CH H 3 3 C H 3 C H 3 C CH 3 H 3 C H 3 C H 3 C luorocyclics 3 9.8 540 2.4 <0.5 M H 3 C
Analytical challenges with volatile methyl siloxanes VMS readily analysed by GC-MS but artifacts from silicone based GC parts e.g. septa, column liquid phases water reacts with PDMS stationary phase to yield D4 incorrect structural assignments - Mass spectra of D4 and H(Me 2 ) 4 -H are identical lab and sample contamination from personal care products clean room facilities needed for low level measurements in water, sediment and biota Abundance 750000 700000 Ion 207.00 (206.70 to 207.70): S3_CC5.D Ion 281.00 (280.70 10.86 to 281.70): S3_CC5.D Ion 355.00 (354.70 to 355.70): S3_CC5.D Ion 429.00 (428.70 to 429.70): S3_CC5.D 650000 600000 550000 500000 450000 400000 350000 300000 250000 200000 150000 D3 D4 D5 13.51 D6 19.40 100000 7.81 Time--> 50000 0 10.86 13.95 16.13 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00
loxanes in Air Samples from Across Canada and on our lab facilities Urban 0.12 Near urban Remote areas 0.08 0.04 0.00 Resolute Little ox L. YK Turkey L. 10-08 Turkey L 10-09 S.S.M. ct 08 L. St Pierre Jl-08 Burlington L. St Pierre Sep-08 Toronto 16 14 12 10 8 6 4 2 0 Concentration (µg/m 3 ) Clean room lab utdoors near WWTP ffice Lab Clean Lab 2 Clean Lab 1 WWTP-B WWTP-A Indoor office Lab M. Alaee, EC Burlington. Unpublished data
Concentration of cvms in Influent, effluent and Receiving Waters of WWTPs in Canada Concentration (µg/l) 100 10 1 0.1 0.01 D4 D5 D6 1E-3 D4 D5 D6 D4 D5 D6 D4 D5 D6 Influent Effluent Receiving water Concentration of cvms are high in influents, lower in effluents and receiving waters M. Alaee, EC Burlington. Unpublished data
PNECs for D4 and D5 Media PNEC Notes D4 Water 0.2 µg/l 14 d LC-50 4.4 µg/l sub-chronic LC50 of 0.01mg/L D4 Sediment 131 µg/g NEC for midge emergence ratio D5 Water 15 µg/l no significant adverse effects at 15 µg/l (solubility) D5 Sediment 70 µg/g NEC for midge development A cross Canada survey of WWTPs and surface waters found no cases in which PNECs for water were exceeded for effluents or for receiving waters rom Environment Canada s risk assessments of D4 and D5
High log Kow and relatively slow biodegradation in fish and invertebrates leads to high predicted and observed bioaccumulation Biomagnification of D5 in the food web of Lake Mjosa (Norway) compared with PCB180 (Borga et al EST 2012 in press) biomagnification of D5 is being governed by species-specific properties such as biotransformation rate or tissue distribution
Modelled environmental distribution of D5 assuming emissions to water only (Hughes et al. Chemosphere 2012) ~0.7% emitted back to air ~5% remains in water Most mass in sediments
Current regulatory status US ederal and State - Assessments: California. ffice of Environmental Health Hazard Assessment literature review 2008 No US EPA siloxane assessment published and they are not on a priority list; DA approved in cosmetics Environment Canada Risk Assessment: January 2009, Environment Canada and Health Canada proposed to add D4 and D5 siloxanes to the List of Toxic Substances under the Canadian Environmental Protection Act, 1999 (CEPA), and to develop regulations "to limit the quantity or concentration of D4 and D5 in certain personal care products. The decision on D5 was appealed by the industry (SEHSC) and reversed; therefore only D4 will be restricted in Canada Europe: UK Environment Risk Assessment published 2009 D5: No risks are identified from the production and all uses of D5 for the air, water, and the terrestrial compartments, nor for humans exposed via the environment D4: No risks are identified for the air, water, sediment, and terrestrial compartments, and nor for predators Uncertainties in the assessment for predators relate to both the BMs and the predicted no-effect concentrations (PNECs) used D4 may be an endocrine disruptor No final EU regulatory decisions:
Possible path forward for an initial study of siloxanes in the S Bay region 1. Measurements of selected fish samples Methodology now in place at Environ Canada could be used although there are potential contamination issues to overcome 2. Surface waters? Methodology available to collect and analyse 3. Modelling emissions to the Bay and environmental distribution based on per capita use and estimated WWTP removal rates?
Concentration of cvms in Sediment Samples & Biosolid Amended Agricultural Soils Concentration (µg/g) 10 1 0.1 0.01 D4 D5 D6 D4 D5 D6 Biosolid amended soil M. Alaee, EC Burlington. Unpublished data D4 D5 D6 Sediment
Global concentrations of volatile methyl siloxanes (ng/m 3 ) measured using passive air sampling devices (Genualdi et al. ES&T 2011) Cyclics Linears