Methylsiloxanes
These artificial, man-made, silicon-based compounds are ubiquitous and have been linked to cancer, endocrine disruption, and developmental, reproductive and liver toxicity.
There is an increasing awareness of, and a growing concern about, the environmental and health hazards associated with methylsiloxanes.
Methylsiloxanes are a class of synthetic chemicals used to produce silicone polymers – materials that are found in an EXTREMELY wide range of products. Methylsiloxanes are silicon-oxygen compounds. Silicone itself is polydimethylsiloxane (PDMS), and low-molecular-weight cyclic siloxanes (D4, D5, D6) exist within this material.
Methylsiloxanes are widespread synthetic pollutants found in the atmosphere, water, and soil, originating from personal care products, industrial processes, and notably, engine exhaust. Recent studies indicate high-concentration, omnipresent contamination (including urban and rural areas), with potential daily inhalation doses that are higher than PFAS and plastics, creating urgent needs for health risk evaluations. In many products, PolyFluoroAlkyl Substances (PFAS) have been replaced by methylsiloxanes. That may not have been an improvement!
Methylsiloxanes, commonly known as silicones, are polymeric compounds made up of silicon and oxygen atoms bonded together. Due to their versatility, high production volume, stability, and local presence in the environment and in biological fluids such as breast milk, fat, and plasma, siloxanes are considered to be persistent organic pollutants that represent a public health problem of which public awareness is just beginning to emerge.
Methylsiloxanes are associated with multiple adverse health effects. The cyclic volatile methylsiloxanes commonly referred to as D4, D5 and D6 are linked to cancer, developmental and reproductive toxicity, endocrine disruption, and liver toxicity. The European Union has classified D4 as an endocrine disruptor and evidence suggests D4 may impair human fertility. High doses of D5 in laboratory tests have shown potential to affect the immune system and cause uterine tumors.
https://www2.mst.dk/udgiv/publications/2005/87-7614-756-8/pdf/87-7614-757-6.pdf
On any given day, people around the world may inhale 1000s of times more methylsiloxanes than microplastics.
Global annual production of methylsiloxanes is estimated to be between 8,000,000 and 10,000,000 tons. China is the largest manufacturer and consumer of methylsiloxanes, producing over 4.5 million tons in 2019, which accounted for roughly two-thirds of global production.
Global annual emissions of methylsiloxanes in vehicle-emitted aerosols are estimated to range from 7-13 million pounds, underscoring the significant yet largely unknown potential for health and climate impacts.
Exposure to methylsiloxanes is common because of their widespread use in industry and across sectors, resulting in their presence in industrial applications as well as consumer and professional products.
Methylsiloxanes—specifically cyclic siloxanes such as D4, D5, and D6—are present in silicone gel-filled breast implants. They are components of the silicone elastomer shell and the filler gel, and they can bleed or diffuse through the shell into surrounding body tissues and blood, even if the implant is intact.
Methylsiloxanes, specifically large molecular polydimethylsiloxanes (PDMS), are emerging as a significant, previously overlooked component of engine exhaust, including those from vehicles and ships, and likely aircraft, as they are present as antifoam additives in lubricants. These compounds can survive high-temperature combustion and are emitted in the particle phase of exhaust.
Methylsiloxanes have been found in primary aerosol particles emitted by ship engines, accounting for up to 1.2% of organic aerosol mass during stable operation and rising to 28.2–59.3% under transient conditions (acceleration, deceleration, idle).
Methylsiloxanes are used as antifoam additives in engine lubricants and fuel oils. During engine operation, particularly during inefficient combustion, lubricating oil enters the combustion chamber, leading to the emission of unburned or partially decomposed compounds in the exhaust.
Methylsiloxanes are commonly present in the atmosphere, with urban areas showing the highest concentrations, often making up 2% to 4.3% of the total organic aerosol mass. Unlike other exhaust components, methylsiloxanes are chemically stable and can be transported over long distances, contributing to their presence in remote areas.
Methylsiloxanes in atmospheric aerosols likely impact rainfall by altering cloud formation and precipitation patterns. Methylsiloxanes are efficient surfactants. As a persistent, hydrophobic pollutant, these large molecular compounds can modify the surface tension of aerosol particles, affecting their role as cloud condensation nuclei (CCN), impact cloud formation, and interfering with ice nucleation, which dictates cloud evolution and rainfall efficiency. Similar to other aerosol types that alter droplet size, these compounds could lead to increased cloud droplet number but smaller droplet sizes, potentially suppressing light rain (cloud lifetime effect). Methylsiloxanes do not degrade quickly, allowing them to remain in the atmosphere as persistent organic aerosols that alter aerosol-cloud interactions over longer periods.
What are Siloxanes?
Siloxanes are often grouped based on properties like molecular structure (cyclic, circular in shape or linear, straight and chain-like), molecular weight, and volatility. Despite these differences, they all share a similar chemical backbone and many common characteristics.
Common cyclic VMS (cVMS) include compounds known as D4, D5, and D6. Common linear VMS include compounds known as L3, L4, and L5.
PDMS
PolyDiMethylSiloxane (PDMS) is used in numerous consumer products and industrial materials, including silicone cookware.
Due to concerns around their persistence, tendency to bioaccumulate, and toxicity, the European Union has adopted a broad restriction on certain cyclic siloxanes, including restricting their use in personal care products and cosmetics.
However, in the U.S., siloxanes continue to be produced at high volumes, and global production is estimated to be over 10 million tons annually. The U.S. Environmental Protection Agency (EPA) reported 2019 domestic production volume for D4, D5, and D6 as between 250 to 500 million pounds, 100 to 250 million pounds, and 1 to 10 million pounds, respectively.
Concerns over siloxanes are not limited to human health hazards. When cosmetics and personal care products containing siloxanes are washed off, they contribute to environmental contamination. A primary concern is related to the chemical stability and persistence of these chemicals in the environment and their ability to bioaccumulate.
The European Union’s chemical regulatory agency, ECHA, has designated multiple siloxanes as substances of very high concern, including VMS compounds L3 and L4 due to their designations as very persistent and very bioaccumulative substances.
As restrictions grow on the use of hazardous per- and polyfluoroalkyl substances (PFAS), siloxanes have been used as replacements in applications like textile treatments and in non-stick cookware.
This results in regrettable substitutions where one class of hazardous chemicals is replaced with another, rather than with safer alternatives.
Millions of people use methylsiloxane-containing skin “moisturizers” even though methylsiloxanes damage even deep layers of the skin. If you use any products that contain methylsiloxanes, or if you know anyone who does, be sure to read: “Evidence of Skin Barrier Damage by Cyclic Siloxanes (Silicones)—Using Digital Holographic Microscopy” below.
Sources include:
breast implants
personal care products (PCPs)
cosmetics
foundations
makeup
brow liners
masks
setting powders/sprays
styling gels/lotions
creams
lotions
moisturizers
shampoos
conditioners
hair styling aids
hair treatment/serums
hair sprays
shaving products
antiperspirants
deodorants
sunscreens
personal lubricants
excipients in topical medicines
children’s products
pacifiers
baby bottle nipples
diaper creams
silicone cookware
baking utensils
dry cleaning solvents
detergents
fabric softeners
adhesives
cleaning products
glass and specialty cleaners
fuel additives
antifoaming agents
lubricants
sealants
polishes
waxes
waterproof coatings
paints
defoaming agents
penetrating oils
Cyclomethicone
Cyclomethicone is a general term used for several types of cyclic siloxanes, but the most common ones in cosmetic formulations include:
cyclotetrasiloxane (D4)
cyclopentasiloxane (D5)
cyclohexasiloxane (D6)
Other names:
amodimethicone
antifoam FD 62
cetearyl methicone
DC 35A
DC 360
DIME, DI-ME
dimethicone
dimethicone copolyol
dimethiconol
dimethyl siloxane
dimethylpolysiloxane
dimethylpolysiloxane hydrolyzate
Dow Corning 200
Dow Corning 561
KO 08
methicone
nylon
phenyl trimethicone
PMS 1.5, PMS 154A, PMS 200A, PMS 300
PNS 25
polydimethylsiloxane
polydimethyl silicone oil
S DC 200
silane
silicones
siloxane
SI-O-SIL SS-101-350
triethoxycaprylylsilane
triethoxycaprylylsilane crosspolymer
trimethicone
trimethylsilylamodimethicone
REFERENCES:
April 18, 2026
Scientists Raise Concerns Over Newly Recognized Pollutant Found Everywhere in the Air
“The findings also suggest that concentrations of methylsiloxane in the atmosphere are much higher than expected,” says Rupert Holzinger, associate professor at Utrecht University who co-supervised the study
These compounds account for about 2 to 4.3 percent of the total mass of organic aerosols, making them among the most abundant synthetic substances in the air. By comparison, PFAS levels in the atmosphere are typically more than a thousand times lower.
April 16, 2026
Newly recognized pollutant widely present in atmosphere
https://www.uu.nl/en/news/newly-recognized-pollutant-widely-present-in-atmosphere
Widespread occurrence of large molecular methylsiloxanes in ambient aerosols
Large molecular methylsiloxanes are widely present in atmospheric particulate matter across diverse environments, including urban, coastal, rural, and forest sites in the Netherlands, Lithuania, and Brazil.
These findings highlight the ubiquity of this emerging pollutant and underscore the urgent need for systematic evaluation of its environmental and human health impacts.
December 2025
In-depth insight into cyclic methyl-siloxanes in waste tires pyrolysis oil (WTPO), high silicon content gasoline, and high silicon content diesel
This study emphasizes that the potential threats posed by silicon-containing molecules in Waste Tire Pyrolysis Oil (WTPO) to the environment, organisms, and industrial equipment should be evaluated in advance of large-scale commercialization.
https://www.sciencedirect.com/science/article/abs/pii/S1743967125003514
October 2025
Silicone bakeware as a source of human exposure to cyclic siloxanes via inhalation and baked food consumption
Silicone-based bakeware is widely used due to its heat resistance, flexibility, and non-stick properties. However, concerns have emerged regarding the potential migration and release of siloxanes from these products into food and indoor air during baking.
https://www.sciencedirect.com/science/article/pii/S0304389425025105
June 2025
Toxicokinetic Profiles and Potential Endocrine Disruption Effects at the Reproductive Level Promoted by Siloxanes Used in Consumer Products
Siloxanes, commonly known as silicones, are polymeric compounds made up of silicon and oxygen atoms bonded together alternately. Due to their versatility, high production volume, stability, and local presence in environmental matrices and biological fluids such as breast milk, fat, and plasma, siloxanes have been considered persistent organic pollutants, representing a public health problem.
The toxicological effects of siloxanes, particularly D4, D5, and D6 included significant endocrine disruption, reproductive toxicity, and liver toxicity.
May 6, 2025
A Review of Contamination Status and Health Risk Assessment of Volatile Methylsiloxanes in Environmental Matrices
https://pubs.acs.org/doi/10.1021/envhealth.4c00245
April 1, 2025
Volatile methylsiloxane levels of settled dust in hair salons: Spatial and occupational exposure trends
https://pubmed.ncbi.nlm.nih.gov/39900275/
September 12, 2023
Methylsiloxanes from Vehicle Emissions Detected in Aerosol Particles
Methylsiloxanes can be found in primary aerosol particles emitted by vehicles based on aerosol samples collected in two tunnels in São Paulo, Brazil.
The concentrations of methylsiloxanes exhibited a significant correlation with both unburned lubricating oils and organic aerosol mass.
[ THIS IS VERY TROUBLING!]
April 2023
Are Si-C bonds cleaved by microorganisms? A critical review on biodegradation of methylsiloxanes
No convincing demonstration of Si–C cleavage by native environmental microorganisms has been found.
February 2023
Cyclic volatile methyl siloxanes (D4, D5, and D6) as the emerging pollutants in environment: environmental distribution, fate, and toxicological assessments
October 25, 2022
Occurrence and Behavior of Methylsiloxanes in Urban Environment in Four Cities of China
Methylsiloxanes were widely found in the air, water, soil and sediment of four cities in China. The concentrations of mkethylsiloxanes in all four environmental media of Zhangjiagang were higher than those in the other three cities (Beijing, Kunming and Lijiang), indicating that the siloxane production plant had a significant impact on the pollution level of methylsiloxanes in the surrounding environment.
July 2022
A large contribution of methylsiloxanes to particulate matter from ship emissions
The chemical and stable carbon isotopic composition of the organic aerosol particles (OA) emitted by a shuttle passenger ship between mainland Naples and island Capri in Italy were investigated. Particulate-phase methylsiloxanes were mainly emitted near the harbor under inefficient combustion conditions. Large contributions of methylsiloxanes were found under inefficient combustion conditions, and considerably lower methylsiloxane emissions were observed under cruise conditions.
https://www.sciencedirect.com/science/article/pii/S0160412022002513
July 2021
Methylsiloxanes in petroleum refinery facility: Their sources, emissions, environmental distributions and occupational exposure
High concentrations of methylsiloxanes, including D4, D5 and D6 and linear analogs with 3–14 silicon atoms (L3-L14), have been detected in crude oil, additives and petroleum products from one petroleum refinery facility in China.
Overall, methylsiloxanes in air and soil samples from this facility were up to four orders of magnitude greater than those from surrounding areas, and plasma concentrations of methylsiloxanes in current workers from this facility were up to two orders of magnitude larger than those from reference group.
https://www.sciencedirect.com/science/article/pii/S0160412021000969
The ultra-classic skin care product scam:
Promote products that trap moisture in the skin and leave a smooth feel on the surface of the skin while actually damaging the deeper layers of the skin itself.
August 13, 2020
Evidence of Skin Barrier Damage by Cyclic Siloxanes (Silicones)—Using Digital Holographic Microscopy
Cyclic siloxanes (D4, D5, D6) are widely used in skin products.
A new skin-imaging technique, digital holographic microscopy (DHM), was used for the first time to investigate the impact of D4, D5, and D6 on the skin barrier.
We observed irreversible damage of the stratum corneum due to the interaction with cyclic siloxanes.
These substances changed:
(a) the first level of the skin barrier through destabilization of the intercellular lipid lamellae and destruction of the corneocyte structure (measured with axial nanometer resolution),
(b) the second level by collapse of not only corneocytes but also of a significant part of the clusters, leading to the loss of the stratum corneum integrity and formation of the lacunae,
(c) the third level as an effect of the change in the surface geometrical topography of the stratum corneum and disruption of the integrity of this skin layer, measured with lateral micrometer resolution.
June 16, 2020
Cyclic Volatile Methyl Siloxanes: Environment Tier II Assessment
August 17, 2015
Indoor Air Pollution by Methylsiloxane in Household and Automobile Settings
The comparatively high concentration of methylsiloxane in these three venues indicates that interior renovation and decoration work, and even travelling in cars, can involve exposure to more serious siloxane contamination during everyday activities.
February 25, 2015
Siloxanes Unexpectedly Observed In Antarctic Soil And Marine Life
The presence of synthetic compounds in such remote ecosystems is always undesirable:
“If a compound is found there, it will be everywhere.”
https://cen.acs.org/articles/93/web/2015/02/Siloxanes-Unexpectedly-Observed-Antarctic-Soil.html
Toxic ingredient to avoid: Siloxanes
Many siloxanes are persistent in the environment. These are classified as “persistent-bioaccumulative-toxic,” i.e., they build up in the environment. One of the most used siloxane is polydimethylsiloxane, a.k.a. dimethicone and PDMS. This ingredient is likely to bioaccumulate in the tissues of organisms. It’s also likely to persist in the environment and be toxic to aquatic life.
Cyclopentasiloxane (D4) is a stable and nonreactive chemical, so can take years to decompose. It may evaporate into the air or enter waterways through drainage systems when rinsed off skin or hair.
If you would like to have a respectful discussion regarding this issue and help work on possible solutions, then please feel free to contact me directly anytime at 310-619-3055 (phone, text, Signal, Telegram or WhatsApp) or James.Roguski@gmail.com
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Just happened to watch this from Geoengineering Watch Global Alert News, April 18, 2026 -
"Every breath we take is contaminated. “Unusual airborne toxin detected in the U.S. for the first time, hidden toxins may be drifting into the air” (ScienceDaily). “Brain-Eating Amoebas May Pose a Growing Global Threat, Scientists Warn” (ScienceAlert). “Mystery ‘skyquakes’ are ripping through the world. And nobody knows why” (BBC). The so called science community doesn’t seem to have a clue about much of anything any more. Perhaps that is their purpose and what they are paid to do, pacify populations until the brutal bitter end.
All are needed in the critical battle to wake populations to what is coming, we must make every day count. Share credible data from a credible source, make your voice heard."
Dane Wigington - https://www.youtube.com/watch?v=OgrQml3Cps0
You are welcome. Your article has made me consider abandoning my BiPAP! It is horrible to wear anyway. It really interferes with lymphatic flow too. I am at an age where if I die in my sleep, I'm good. All of my health efforts, at this point, are for functionality - not longevity. And, I am good with God which is the most important thing. Thanks for all your great articles.