NEW "HEALTH RISK ASSESSMENT OF MODACRYLIC FIBERS" IN MATTRESSES: 

What They Found, What They Hid, and Why You Are Still at Risk


Reading Between the Lines

A new "Quantitative Health Risk Assessment" was published last October regarding the safety of mattress fibers. It was a very in-depth study required by the new California law that is banning fiberglass from mattresses and furniture by 2027, as well as the use of Antimony Trioxide in any fibers (like modacrylic ones) that will still be allowed as fire retardants.

The industry is currently patting itself on the back, claiming these (presented as) "new" fibers, coated in flame retardant chemicals, are seemingly "replacing" fiberglass and are "safe."

Here is how the 157-page report begins:

"ISPA is pleased to report that even with overly conservative assumptions and multiple pathways assessed for unlikely chronic exposure, based on the findings of the Report, the conclusion is that expected exposures to modacrylic fiber without antimony used in a fire-retardant barrier in mattresses in the normal course of consumer use do not confer a health risk to humans." — From "RE: Quantitative Health Risk Assessment of Modacrylic Fiber Without Antimony Trioxide"

Let's start by decoding what this is really saying. First, they have to throw in "overly conservative assumptions." Then, notice it specifically states "modacrylic fiber without antimony" and mentions "the normal course of consumer use." The conclusion? These specific fibers "do not confer a health risk to humans."

Basically, one can assume that antimony is still dangerous even when chemically bonded or coating the fibers, but we can't say that for sure—because they curiously did not test fibers with antimony. They made sure to note this distinction, even in the title.

The new California law specifically bans the use of Antimony in any fibers that can still be used in mattresses. So, let's go back to the only other study that has been conducted and made publicly available, from February 2022: "Fiberglass and Other Flame-Resistant Fibers in Mattress Covers" published in the International Journal of Environmental Research and Public Health.


THE REAL SCIENCE: What is Actually in Your Mattress?

Fiberglass, sometimes referred to as man-made vitreous fibers (MMVF), is a known respiratory, skin, and eye irritant and an asthmagen. In occupational settings, fiberglass exposure has been correlated with recurrent chest infections and pulmonary fibrosis. These fibers are predominantly amorphous mixtures of oxides of silicon, calcium, and other metals.

Prompted by historical concerns that chronic inhalation could pose lung cancer risks, the IARC reviewed the literature and concluded in 2001 that the evidence met the criteria for Group 3 (unclassifiable as to human carcinogenicity). However, the carcinogenicity of a fiber depends heavily on its inhalability (size) and biopersistence (durability in the lung) .

The "Sock" Secrets: Antimony and Vinyl Chloride The 2022 independent study aimed to fill information gaps by analyzing new mattress covers using microscopy. What they found in the "socks" wrapping the fiberglass was alarming:

The presence of fiberglass was not disclosed on the labels of the most popular brands of the tested mattress, leaving consumers unaware and some tried to tuck the disclosure away on a less visible tag and not directly on the prominent "law label".


THE REAL-WORLD DANGER: Fragmentation and Leakage

The new 2025 industry report claims safety based on "intact" fibers. This means fibers that stay contained inside the mattress. The study did not go any further than this and therefore does not apply to fibers that escape the cover-whether it be through it's removal, normal wear and tear, or just by making their way out through normal use which many have discovered to eventually happen as the covers are very thin and cheaply made- and potentially become airborne or that would come directly in contact with humans/animals in any way. As we all know, this is the real life danger, when the fibers come out of the mattress. This is when things become dangerous and out-of-control and the scenarios that need many different kinds of testing. The 2022 study touched on the physical reality of what happens to these materials, noting that further testing was needed:

The Case of the 6-Year-Old Child This isn't just theoretical. In one case investigated by the CDPH in 2021, a 6-year-old child suffered persistent skin and respiratory irritation linked to fiberglass leakage from a mattress purchased in 2018. The home required a massive cleanup, including the disposal of the mattress, carpet, and clothing.

Children, infants, and pets represent a "special potential risk group," both due to increased susceptibility and the likelihood of jumping on beds, which exacerbates fiber breakage. Additionally, children, babies, and animals are lower to the ground, and dogs use their noses to sniff and navigate their world. Unfortunately, these are our beloved babies that we are responsible for, and they depend on us to protect them from dangers like this. But how can we when you cannot see the danger and have no clue? Both babies and pets often put hands and toys in their mouths, and the terrible itching and other symptoms frequently mimic allergies. Tragically, due to the invisible nature of the fibers and a general lack of awareness, unknown contamination of homes and belongings can go undiscovered for months or even years. This has been a horrific reality many have had to face, including myself. No one should ever have to go through this. Today, people are still joining our group with the same heartbreaking stories every day. 

Some brands have quietly shifted to allegedly not using fiberglass in their mattresses anymore, but what about all the ones still in circulation or are currently sitting in the homes of the next unknowing victims?

Here is an unsettling fact: some of the groups of the the fibers tested in the 2022 study were from a popular brand that was the one of the top-selling brands on one of the main online retailers here in the US, across the span of the most recent years. During this time period, those mattresses all contained fiberglass and the modacrylic fibers that were tested and revealed to have the chemical properties of Antimony Trioxide. Alarm bells should be ringing. Check your mattress tags for fiberglass or modacrylic fibers, research online, and most importantly, NEVER REMOVE YOUR MATTRESS COVER. These mattresses are still in thousands of homes and in circulation. If your mattress was manufactured in 2024 or earlier, there is a major chance that it is one of these dangerous mattresses. Even if there is a zipper or no warnings or disclosures of fibers, DO NOT REMOVE THE COVER. This is what leads to the almost immediate contamination of homes. The fibers become airborne and spread like invisible wildfire, carried through the HVAC system and distributed everywhere. They cling to everything, and most belongings have to be discarded, including clothing and material items. The cleanup is extensive and can take months. It involves bagging up everything and a thorough, planned-out, meticulous deep clean. Experts warn against DIY cleanup as it is not safe or fully effective. Professional remediation is required in most cases, as specific professional equipment and proper training are necessary to be effective. This costs in the tens of thousands, which many cannot afford, leaving them forced to do their best at making their homes safe again on their own.


THE INDUSTRY'S "OFFICIAL" FINDINGS: A Lie of Omission

The new assessment, conducted by INTERTOX for the International Sleep Products Association (ISPA), focused on Modacrylic Fiber Without Antimony Trioxide. Keep in mind, this testing only applies to "intact" fibers, still contained inside the mattress.

What They Found:

The Antimony Loophole We return to that specific title: "Modacrylic Fiber Without Antimony Trioxide." As we learned, for years, major brands used modacrylic fibers loaded with Antimony Trioxide. And we only know this because of the 2022 study that forced this information into the public but has not been talked about, anywhere.  Despite California banning it, the industry and the CPSC have managed to keep all of this out of the media and brands quietly switched recipes and refuse to inform the public  and made sure to leave the antimony out of the testing in this new, inadequate mandatory study.

Beyond the ban, we urgently need a national recall and a comprehensive public awareness campaign to provide critical information and resources for those affected. Currently, there is absolutely no funding, help, or assistance available for victims. Tragically, most people are not taken seriously; instead, they face systemic gaslighting—their situations are downplayed, and they are made to feel as though they are overreacting or irrational, rather than being believed. 

The "Intact" Myth The study relies on "emissions testing"—seeing if fibers release gas while sitting perfectly sealed inside a mattress. This is a smoke and mirrors show. The real-world nightmare begins when the fibers leave the mattress. When you unzip that cover, or when the cheap fabric tears, those fibers don't just "off-gas." They shatter. They leak. They become airborne. They take over. They took away my precious Nero from me and stole his life from him.

The testing described in this briefing does not account for fibers being pulverized into dust, floating in your air, landing on your skin, getting in your eyes, and being inhaled or consumed by you and your pets.


WE ARE THE TEST SUBJECTS

I lived with these fibers all over my home for almost a year. You can’t see them, so we didn’t know. We were consuming them, inhaling them, and living in a cloud of modacrylic chemically-coated fibers and fiberglass particles. They covered every inch of our home, cycling through our HVAC, constantly breaking down into smaller, more dangerous particles.

They didn't test for that scenario. WHY?

A Tragic Consequence We don't know the full extent of the dangers these chemicals impose on the human body when inhaled or consumed in fiber form. But I do know that they can be deadly.

My dog, Nero, died from his exposure to and consumption of these fibers at only 3 years old. We found ourselves in an emergency vet one late night and discovered he developed a cranial tumor and a large mass that covered the inside of his chest. He had lost his mobility after a rapid and devastating decline and at this point, it was too late. He passed away in my arms the next morning. 

There is a lot of shadiness going on here. If you have a mattress purchased before 2024, you need to be aware. It likely contains the fiberglass and modacrylic fibers with antimony trioxide that this new report conveniently avoided testing. They were never recalled. No one is talking about this.

They know the truth. They just don't want everyone to figure it out.


You Do Not Have to Fight This Alone

 If you suspect your mattress is dangerous or are already living through the nightmare of contamination, you do not have to navigate this crisis in isolation. We created the Mattress Fiberglass Support & Awareness Group on Facebook to provide the transparency and support that the industry refuses to offer. Our community is a safe space where thousands have come where we share our stories, give and get support, access verified identification guides and factual information, and learn how to protect themselves and  the best methods of effective cleanup via guides and talking to others. Whether you need help checking your tags, have questions, or could benefit from emotional support or jsut talking with friendly people who truly understand and have been there, we are here for you. Find us on facebook at facebook.com/groups/donotremovethecover and access our website of resources, guides, a new awesome interactive app with an AI helper, and information at mattressfiberglass.org


Nero was the sweetest American Staffordshire mix- always happy, vibrant, and full of life; he loved meeting new friends and was our ray of sunshine. He would be happy to know that his story is helping save other furry friends from getting sick and families from having to suffer.







Here is a factual briefing of facts from the Q u a ntit ati v e H e alt h Ri s k A s s e s s m e nt of M o d a cr yli c F i b er W it h o ut A nti m o n y T ri o xi d e  :


Briefing: Quantitative Health Risk Assessment of Modacrylic Fiber in Mattresses

Executive Summary

This briefing synthesizes the findings of the quantitative human health risk assessment (HHRA) titled, "Quantitative Risk Assessment of Potential Human Health Effects from Exposure to Residual Modacrylic Monomers in Modacrylic Fiber Without Antimony Trioxide Used in Mattresses," dated October 1, 2025. 


The assessment, prepared by INTERTOX for the International Sleep Products Association (ISPA), 

concludes that the use of these modacrylic fibers in mattress flame-retardant (FR) barriers does not confer a health risk to consumers.


This assessment was conducted to fulfill the requirements of California Assembly Bill 1059 (AB 1059). It evaluates potential exposure to four residual chemicals of interest (COIs): acrylonitrile (AN), vinyl chloride (VC), vinylidene chloride (VDC), and free chlorine.

Core Findings:

• No Detectable Chemicals: Laboratory testing of three representative modacrylic fiber types found no detectable levels of any COI released through emissions (off-gassing) or sweat-mediated extraction. This core empirical finding suggests a lack of exposure under typical use conditions.

• Conservative Risk Modeling: Despite the non-detection of any COIs, the assessment employed a highly conservative, health-protective methodology, adhering to U.S. Environmental Protection Agency (EPA) guidelines. For risk calculations, it was assumed that COIs were present at a concentration equal to one-half the laboratory's method reporting limit.

• Noncancer Risk is Negligible: The calculated noncancer Hazard Index (HI) for all three monomers (AN, VC, VDC) in both children and adults is significantly below 1, the threshold of concern. While the HI for chlorine in children was calculated at 1.7, the report demonstrates this is an artifact of multiple compounding conservative assumptions and does not indicate an actual health risk. Adjusting for a realistic fiber content (50% vs. the modeled 100%) lowers the HI to 0.84.

• Cancer Risk is Within Acceptable Limits: The calculated Lifetime Excess Cancer Risks (LECRs) for the monomers are within the acceptable risk range of 1 in 10,000 established by the U.S. EPA and below the "no significant risk" level of 1 in 100,000 defined by California's OEHHA.

Ultimately, the combination of empirical non-detection and risk calculations based on worst-case theoretical assumptions provides a robust basis for the conclusion that these materials are safe for their intended use in mattresses.

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1.0 Background and Objectives

1.1 Regulatory Mandate

The assessment was commissioned by the International Sleep Products Association (ISPA) to comply with Section 19101(d)(1) of the California Business and Professions Code, as enacted by Assembly Bill 1059. This legislation requires ISPA to submit a quantitative health risk assessment of modacrylic fiber (used without antimony trioxide) to the Bureau of Household Goods and Services by October 1, 2025. The assessment was performed by Heidi C. O'Neill, PhD, a board-certified toxicologist with the firm INTERTOX.

1.2 Subject of Assessment

The study focuses on modacrylic fiber, a copolymer produced from acrylonitrile (AN) monomers (35% to 85%) and either vinyl chloride (VC) or vinylidene chloride (VDC) monomers. This fiber is used in internal flame-retardant (FR) barriers in mattresses to comply with the federal open-flame flammability standard (16 C.F.R. Part 1633).

Three types of modacrylic fiber manufactured by Kaneka Corporation without antimony trioxide were analyzed:

• Kanecaron SB® (currently used in mattress barriers)

• Protex F® (developed for such use)

• Protex PBB® (developed for such use)

1.3 Chemicals of Interest (COIs)

The assessment focuses on potential exposure to four COIs:

1. Acrylonitrile (AN)

2. Vinyl Chloride (VC)

3. Vinylidene Chloride (VDC)

4. Free Chlorine

The report notes that modacrylic polymer is a stable product. The input monomers (AN, VC, VDC) are chemically bound and not expected to be released. Industrial manufacturing processes are designed to remove residual monomers and prevent their release. However, to be "highly conservative and health protective," these chemicals were selected as COIs for the risk assessment.

1.4 Assessment Objectives

The primary objectives of the HHRA were to:

• Collect appropriate data to estimate the amounts of residual COIs that may be released from modacrylic fiber.

• Use the gathered data, exposure models, and toxicological information to derive quantitative risk estimates for potential adverse health effects, specifically noncancer and cancer risk.

2.0 Methodology and Exposure Assessment

2.1 Guiding Principles

The HHRA was conducted following established risk assessment guidelines from the U.S. EPA. A foundational principle of the assessment is its conservative, health-protective stance. The methodology assumes that if any residual COIs were present, exposure could occur via three primary pathways during sleep:

• Inhalation: Off-gassing of volatile COIs from the fiber.

• Dermal Absorption: Transfer of COIs to the skin via sweat, followed by absorption.

• Oral Ingestion: Hand-to-mouth transfer after direct contact with the fiber.

The assessment also conservatively assumes that for any given chemical, simultaneous exposures from these different pathways are additive.

2.2 Laboratory Testing and Data Collection

To quantify potential COI release, samples of the three modacrylic fibers underwent emissions and extraction testing.

• Emissions testing used gas chromatography-mass spectrometry (GC-MS) for AN, VC, and VDC, and ion chromatography (IC) for chlorine.

• Extraction testing used artificial sweat (per standard EN 16711-2) to simulate sweat-mediated transfer, followed by analysis with GC-MS and IC.

The results from all tests on all fiber samples were definitive:

Testing found no detectable levels of AN, VC, VDC by emissions testing or free chlorine by emissions testing or AN, VC, VDC and total chlorine by sweat-mediated extraction in all modacrylic fiber samples tested.

2.3 Conservative Exposure Assumptions

Despite the non-detection of COIs, the HHRA proceeded with risk calculations by making a critical health-protective assumption, as recommended by the U.S. EPA:

• Assumption of Presence: The calculations assumed that COIs were released in amounts equivalent to one-half of the relevant method reporting limit (RL). The RL is the lowest concentration a method can reliably and accurately report.

Other conservative assumptions built into the model include:

• Constant Release: The COIs are assumed to be released at the same rate over the entire lifetime of the mattress (6 years for a child, 14 for an adult), even though any volatile residuals would off-gas rapidly and not represent a continuing source.

• Direct Contact: The models for dermal and oral exposure assume direct contact with the FR barrier, whereas in reality it is an internal component separated from the user by multiple layers (e.g., mattress pads, covers, sheets).

3.0 Risk Characterization and Key Findings

3.1 Noncancer Risk Assessment

Noncancer risks were evaluated using the Hazard Index (HI) approach. The HI is the sum of Hazard Quotients for all exposure pathways. An HI below or equal to 1 indicates that adverse health effects are not expected.

The calculated HIs were below the threshold of concern for all monomers.

Table 1: Estimated Noncancer Hazard Indices (HIs)

Chemical

Child HI

Adult HI

Acrylonitrile

0.071

0.044

Vinyl Chloride

0.0017

0.0010

Vinylidene Chloride

0.059

0.040

Free (emissions) or Total (extraction) Chlorine

1.7

0.39

The HI of 1.7 for chlorine exposure in children is greater than 1, but the report concludes this does not indicate a human health risk due to the following compounding conservative factors:

• Total vs. Free Chlorine: The calculation is based on the RL for total chlorine from sweat extraction tests, which includes stable chloride salts. No free chlorine was actually detected.

• No Off-Gassing Assumed: The model assumes any residual free chlorine would remain for chronic exposure, when in reality it would off-gas within minutes.

• Unrealistic Fiber Content: The model assumes the FR barrier is 100% modacrylic fiber. In practice, these barriers contain no more than 50% modacrylic fiber. At 50% fiber content, the child HI drops to 0.84. The HI only reaches 1 at a 60% fiber content.

• Highly Protective Toxicity Value: The EPA Reference Dose (RfD) used to calculate the risk is based on a No-Observed-Adverse-Effect Level (NOAEL) from a two-year rat study. This NOAEL was then divided by uncertainty factors totaling 100, making the RfD 100 times lower than a dose at which no adverse effects were observed.

3.2 Cancer Risk Assessment

Cancer risk is expressed as the Lifetime Excess Cancer Risk (LECR), representing the additional probability of an individual developing cancer over a lifetime due to exposure. The U.S. EPA generally considers risks between 1 in 1,000,000 (1x10⁻⁶) and 1 in 10,000 (1x10⁻⁴) to be an acceptable range. California's OEHHA generally considers a risk below 1 in 100,000 (1x10⁻⁵) as "no significant risk." Chlorine is not classified as a carcinogen and was not assessed.

Table 2: Estimated Lifetime Excess Cancer Risks (LECRs)

Chemical

Child LECR

Adult LECR

Acrylonitrile

3.3 in 1,000,000

5.0 in 1,000,000

Vinyl Chloride

1.1 in 1,000,000

1.6 in 1,000,000

Vinylidene Chloride

7.1 in 1,000,000

2.1 in 1,000,000

While these values exceed the 1 in 1,000,000 "point of departure," they are all well within the U.S. EPA's acceptable risk range and are below OEHHA's "no significant risk" threshold. The report concludes that given the cascade of health-protective assumptions used to generate these numbers from non-detected chemicals, the results are not indicative of a human health risk.

4.0 Toxicological Profiles of Chemicals of Interest

The HHRA reviewed extensive toxicological data for each COI from authoritative sources like the U.S. EPA and the Agency for Toxic Substances and Disease Registry (ATSDR).

• Acrylonitrile (AN): Associated with neurotoxicity (headaches, dizziness, impaired judgment), respiratory effects (nasal/throat irritation), and gastrointestinal symptoms in humans at high occupational exposures. Animal studies show increased incidence of astrocytomas of the brain and spinal cord. The International Agency for Research on Cancer (IARC) classifies AN as Group 2B (Possibly carcinogenic to humans).

• Vinyl Chloride (VC): Chronic exposure is linked to significant hepatic (liver) effects, including liver cirrhosis and angiosarcoma. It is also associated with neurotoxicity, immunotoxicity, and developmental effects in animal studies. IARC classifies VC as Group 1 (Carcinogenic to humans).

• Vinylidene Chloride (VDC): The primary noncancer effects observed in animal studies are renal (kidney) toxicity, including tubular injury and necrosis, and developmental effects such as delayed ossification. IARC classifies VDC as Group 2B (Possibly carcinogenic to humans).

• Chlorine: A strong irritant. Acute, high-concentration exposure in humans can cause respiratory effects (coughing, chest pain), dermal irritation and burns, and neurological symptoms (headache, dizziness). Long-term animal inhalation studies show nasal lesions. Chlorine is not classified as a carcinogen by major health agencies.

5.0 Overall Conclusion of the Assessment

The quantitative human health risk assessment evaluated potential risks from residual monomers and free chlorine in modacrylic fibers used in mattress FR barriers. The core conclusion, based on both empirical laboratory data and highly conservative risk modeling, is that these products are safe for consumer use.

Key points supporting this conclusion are:

1. No COIs were detected in any of the modacrylic fiber samples tested.

2. The risk assessment was performed using a series of health-protective assumptions, most notably by modeling exposures to chemicals that were not actually found.

3. The resulting calculated noncancer and cancer risks fall below or within acceptable risk thresholds established by federal and state regulatory agencies.

The report concludes with high confidence:

"The use of modacrylic fibers without antimony trioxide in an FR barrier in mattresses in the normal course of consumer use do not confer a health risk to humans."

This assessment's findings are based on the scientific literature and regulatory determinations as of October 1, 2025.

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Appendix: Report Details

• Full Title: Quantitative Risk Assessment of Potential Human Health Effects from Exposure to Residual Modacrylic Monomers in Modacrylic Fiber Without Antimony Trioxide Used in Mattresses

• Date: October 1, 2025

• Prepared For: International Sleep Products Association (ISPA)

• Prepared By: Heidi C. O'Neill, PhD, Diplomate, American Board of Toxicology (DABT)

• Firm: INTERTOX