SOT2024 (March 10-14, 2024) Report
By Addis Klemann (佐藤圭吾), Technical Assistant
The SOT 2024 was my first SOT event that I had attended. I was impressed by
the large amount of support for the event and participation from around theworld. The event had both public entities and private companies who wereactively involved research but also creating new regulations and new scientifictechniques to discover and utilize for the betterment of society. The event wasaround one week and held at Salt Lake City, Utah in the US. I was very
impressed that SOT had large number of scientists from around the world at theevent. The event consisted of chemists, biologists, clinicians, environmental
scientists and others who all presented the latest topics in toxicology. This
event gave me a very positive view for science moving forward even afterconcerns of the post COVID-19 era. People are more passionate to share theirexpertise and tackle issues not just in the USA but also the world aboutchemical use in daily life but also in the industrial setting. New discovery of toxic
chemicals such as new emerging PFAS, pesticides and more offer new insight
to what is necessary in the foreseeable future in order to create a healthiersociety. More events like SOT should take place around the world to ensure
healthy promotion of science but also increase our understanding of theenvironment and technology we use moving forward for the greater good.

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I. POHaD (Paternal Origins of Health and Diseases)
II. Micro-Nano plastics
III. PFAS
IV. Neurotoxicology
V. Emerging issues
VI. Microbiology
VII. Risk assessment

I.

POHaD (Paternal Origins of Health and Diseases)

Symposium Session: It Takes Two! Paternal Exposures and Their Impacts
on Offspring Health
1. Paternal Environmental Exposures and Their Influence on Development via
the Sperm Epigenome. by Dr. Kimmins from McGill University (Abstract #1215)
The first topic was introduced by the presenter who specialized on the paternal
germline. According to Kaati et al., too much food availability before puberty in
grandfathers (8-12 y.o.) was associated with increased risks of diabetes andcardiovascular diseases in their grandchildren. This suggested that there was
the possibility of environmental reprogramming on the sperm epigenome
through food. The paternal germline is the genetic material passed from thefather to the offspring. The functional genotype that was focused on werealtered sperm, transmission at the fertilization stage and the escape of
reprogramming cellular memory exposure in subsequent generations. The
presenter looked at sperm epigenome and paternal histone modifications which
would influence the histone environment. Histones are essential proteins which
provide structural support for the chromosome.
An important histone mentioned was H3K4me3, which is sensitive to paternal
folate deficiency and alters offspring development. It was observed that sperm
genetic material changes are transmitted and persisting in the embryo alongwith an association with embryonic gene expression. The presenter has shownthat 25% of promoters that have altered H3K4me3 in sperm and embryos haveshown deregulated gene expression.
The presenter then changed the topic to DDT used for malaria vector control
which was associated with male reproduction health. The presenter has alsomentioned that the accumulation of DDT and DDE were detected even in thearctic due to bioaccumulation in the region. It was also revealed that DDT and
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DDE are health risks that is associated with neurodevelopment andneurofunction. The presenter also mentioned that DDT exposure has an
association with differentiation of H3K4me3. This is seen by environmental
changes in sperm and a reduction of H3K4me3 occurs in developmental genes.
The presenter concluded that we should focus on male health as an important
subject to study for paternal health.
2. Aberrant Sperm DNA Methylation following Wildfire Smoke Exposure in Miceand Humans. by Dr. Montrose from Colorado State University (Abstract#1216)The presenter has shown data that in recent years there has been an increasein wildfire activity around the world. According to the presenter, in 2023, theCanadian government has spent over one billion dollars on fighting wildfires
which was the most ever recorded for the government. There is also an
increase of Particulate Matter (PM) 2.5 due to wildfires across the US andCanada regions. The presenter has shown that there are 3 categories of PM
which consist of size, chemical composition and dose. An example ofoccupational hazard was mentioned when firefighters working in the wildfire
environment were associated with health risks of neurocognitive dysfunction
and fertility issues.
Smoke primarily affects the lung and heart which causes cytokines andchemokines to be released into the body to fight the effects of smoke in the
body. The presenter has shown the data that PM is linked to a deterioration of
sperm quality. A study on wildfire firefighters in Portland, Oregon has found thatlower sperm concentration was detected after wildfire exposure. It was alsomentioned that female firefighters were about 2 times more likely to have a
miscarriage than nurses.
In a mice study, they found that exposure to wildfire smoke led to sperm DNA
methylation caused by the exposure led to epigenetic inheritance to beplausible, however more studies are needed to confirm. The presenter has
concluded that more studies of wildfire smoke are necessary as it is a growing
risk of concern.

II.

Micro- Nanoplastics

Platform session: Micro- and Nanoplastics
1. Understanding the Health Risks of Micro- and Nanoplastics exposure in
Humans by Dr. Hernandez from Autonomous University of Barcelona(Abstract #2077)
The presenter has explained that Micro-Nanoplastics (MNPs) have similarities
to nanomaterials which have a high capacity with biomolecules and are used in
the medical field. It was also emphasized by the presenter that support for3

better policies of risk evaluation is needed to identify more MNPs and toaddress knowledge gaps.
The presenter showed a list of items which need to be addressed to improvethe understanding of health risks which MNPs impose. Such as the difficulty ofhazard assessment due to lack of regulations and specific rules, lack of existing
human models and biomarkers which make it difficult for scientists to have adefinitive conclusion on the impact of human health of MNPs. It was also statedby the presenter that there is a need to study measuring equal cell exposure of
MNPs along with the study of kinetics. This is due to absence of understandingof the mechanisms of MNPs related to health risks in the human body. Also, theauthor has emphasized that there should be more studies of chronic exposureof MNPs to look for in health risk assessments. At last, the author introduced
the large-scale EU project, “PlasticHeal” (https://www.plasticheal.eu/en) which is
aimed at developing novel tools to study MNPs’ mode of action and impact of
MNPs in human health. The presenter also mentioned that more studies ingenotoxicity, methodologies and complex in-vitro studies should be pursued tocontinue the evaluation of health risk assessment of MNPs in human health.
2. Utilization of Non-targeted Chemical Analysis and In-vitro Studies to Assess
the effects of Primary-sourced and Secondary-sourced Microplastics Dosedin Simulated Lung Leachates and Extracts by Rios-Colon from RTI
International (Abstract #2079)
The presenter gave an explanation that primary microplastics were related tomicrobeads, while secondary microplastics are found from products. Primaaryand secondary microplastics have aged and unaged microplastics particles.
MNPs have the potential to be physically or chemically affected. It is also known
that tire rubble is detected by FTIR (Fourier Transform Infrared Raman
Microspectroscopy) for the aging process of MNPs. In the research presented, it
was revealed that increase in tire rubble concentration was linked to a rise in
Reactive Oxidative Stress (ROS) in lung cells. Aged tire rubble particles wereassociated with a rise in inflammatory biomarkers which increased the dose andexposure of MNPs. MNPs leachate studies have concluded that there is adifference between specific shredded polymers and manufactured microbeads
in MNP studies. The presenter concluded that measuring both physical andchemical properties were needed to understand MNPs in more detail affecting
the human body.
3. In-vitro Toxicity of Microplastic Fibers to Human Lung Epithelial Cells
Cultured at an Air-liquid Interface by Dr. O’Conner from University of Florida(Abstract #2080)
The presenter has mentioned that in the lungs, the most common microplastics
are Polypropylene (PP) and Polyethylene terephthalate (PET). In the lungs it isalso found that the most common forms of the plastics are fibers and films. An
emerging issue of Azobenzene Disperse Dyes (ADD) was mentioned, which is
4being used in 70% of industrial dye, used to color synthetic fiber. The color
violet is the most toxic color used which affects dendritic cells and causes IL-1β,
IL-8 and IL-10 activation. In the study, it was also noted that the violet color was
more associated with cancer compared to other dyes and none dyed plastic
samples. This is due to the association with ferroptosis (programmed cell deathby iron and accumulation of lipid peroxides) signaling pathway along with NRF2
mediated oxidative stress response. It was also found that undyed fibers wereassociated with inflammation, negative effects on wound healing process and
ROS. Dyed fibers are known to be associated with DNA mutation effects and arisk of cancer. The presenter concluded that dyed samples of plastics might bepartially responsible for plastic film and fiber risks in the human lungs.
4. Assessing Toxicity of Amorphous Micro- and Nano-plastics on Bronchial
Epithelial Cells using Air-liquid Interface Models by Dr. Gosselink from the
School of Nutrition and Translational Research in Metabolism (Abstract#2081)The presenter introduced the topic that MNPs can be found in the human lungand be able to cross the bronchial epithelial barrier. The presented study
mentions that PP exposure induced Interleukin-8 (IL-8) protein secretion in asubmerged test of nanoparticles. Polyamide exposure was mentioned tonegatively affect IL-8 levels and apoptosis when tested in nanoparticles. A
droplet test was also conducted in the study of air exposure effects ofnanoparticles. The results have shown that IL-8 levels in air exposure had no
adverse effects on IL-8 levels, it only seen a slight negative minor impact on
bronchial cells when affected in air exposure environment. The presenter
concluded that the variety of MNPs in polymer type, size, exposure length tends
to have different outcomes when it comes to the research about MNPs. It wasalso mentioned that more particle studies should be conducted when it comesto human health as more data is needed.
5. Cellular Responses to Nanoplastics: Implications for Exosome Release forExtracellular Nanoplastics Transport, and Cellular Toxicity by Dr. Lee from
University of Iowa (Abstract #2082)
The presenter gave an introduction of the role of exosomes (nanosizedorganelles) which are released when exposed to nano-plastics (NP), this wasshown in a dose-dependent model. It was shown that exosomes were able toremove NPs to the extracellular space to maintain cellular homeostasis. Due tothis, a disruption of glucose homoeostasis and the increase of insulin wasobserved when tested in mice. An increase of weight and overall adiposity wasseen including adipose immune cells. Gene expression changes were also
seen where it saw a promotion of adipogenesis and showing signs ofhyperglycemia. Gut microbiome changes were also observed and a decrease inbeta diversity, which looks at the ratio between regional and local species
diversity in the gut environment. As a result, leads to weight gain in the mice.
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Signs of atherosclerosis were also seen when a decrease of propionic acid wasobserved. Propionic acid is responsible for the metabolic breakdown of fatty
acids, this can affect high blood pressure leading to CVD symptoms. It was alsomentioned that altered gene expression which have seen increased leukocyte
activity is also linked to CVD symptoms. To try to mitigate the symptoms, thepresenter tested delphinium which is a purple flower that has antioxidant andanti-inflammatory properties. The delphinium testing was able to see weightgain loss and saw deregulation cAMP and PPAR signaling in adiposity. To
conclude, the author stressed that more studies are needed that look at
exosomes and other nanosized organelles to further understand the impact of
microparticles in the human body.
Hot Topic Session: Translational Insights into Reproductive Impacts ofMicro- and Nanoplastics Contamination
6. Challenges and Solutions to Quantifying Micro- and Nanoplastics in
Biological Specimens by Dr. Yan, Columbia University (no abstract number)This session looks at how to quantify Micro-Nano plastics (MNPs) in theenvironment and the biological systems. To get the samples from theenvironment, the presenter used modern laboratory techniques such as gravity
separation and removal of natural organics with water. The presenter also
showed the use of hyperspectral dark-field microscopy, a novel technique which
is cheaper and quicker for looking at nanoparticles from the size of 5nm. This isthen used for Identifying the MNPs and further testing is done with a novel
technique called Py-GC/MS (Pyrolysis- Gas Chromatography-Mass
Spectrometry). This technique allows samples to remove macromolecules using
acids and bases manipulation.
The presenter also looked into novel technique like Nile Red Staining, which iscapable of looking at lipids in microorganisms and FTIR (Fourier transform
infrared Raman microspectroscopy) which can look at MNPs but also can lookat lipid collection from cells which can identify microorganisms’ behavior within
MNPs. This could give us great insight into how the body can potentially beaffected by these MNP interactions with living organisms. The presenter
concluded that with the combination of novel techniques mentioned should bestandardized by the National Institute of Standards and Technology (NIST) due
to the importance of having MNP research more accredited and be able toproduce more data with confidence.
7. Comparative Quantitation of Testicular Microplastics Accumulation in Dogs
and Humans and Associations with Sperm Count. by Dr. Yu from Universityof New Mexico (no abstract number)This session started with the topic of reproduction system levels of MNPs
stating that studies are still scarce and the association of sperm quality isrelatively unknown. It was found that there was an increase in TDS (Testicular6

Dysgenesis Syndrome) which was linked to testicular cancer and poor semenquality. In the study, the author was able to look at a correlation between an
increase of plastics to a decrease in sperm count. The authors collected 47
male reproductive tissues from routine dog neuter surgeries. Human testis
samples from 23 deceased individuals, aged 16-88, were also obtained. They
quantified 12 types of plastic polymers by using Py-GC/MS from both canineand human samples. In dogs, it was revealed that different microplastic
contamination profiles were seen in testicular tissues in individual canines.
Mean total MNPs levels were 122.63µg/g in dogs and 328.44 µg/g in humans.
They were able to observe that PVC, PET PC, but ABS (Acrylonitrile butadienestyrene) had the most significant impact on sperm count. It was also revealed
that dogs share more MNP concentrations and compositions compared tohumans. The presenter concluded that increased global awareness anddevelopment of mitigation to safeguard male fertility is crucial for reproductive
health.

III.

PFAS

Risk Communication of PFAS: Challenges and Opportunities:
Informational Session
1. PFAS Risk Communication from an NGO Perspective by Ms. Benesh from
Environmental Working GroupPFAS risk has been mentioned since the 1950’s from industrial review of PFAS
use. This was followed by the 1960’s discovery of PFAS linked to animal
toxicity. It was stated that regulators like FDA (Food and Drug Administration)
knew of the existence of PFAS risk as early as 1966. The Department of
Defense (DOD) has also shown that it knew the risk of PFAS but does not ban
its use due to quoting “can’t live without PFAS”. This is due to number of
products used in PFAS such as plastics, gaskets and fabrics which have waterand oil repellent qualities. In conclusion, Ms. Benesh argues for PFAS bans ondrinking water along with tap water to resolve the PFAS issues.
2. Global Collaboration on Managing PFAS Chemical by Ms Eeva Leinala from
OECD (Organisation for Economic Cooperation and Development)This session explained the implementation of the guidelines for terminology for
PFAS. This was based on standardized tools needed to improve communicationof molecular structural traits when it comes to PFAS. Another implementation
measure suggested was the inclusion of synthesis reports should be noted onpolymeric PFAS. Such as life cycle, hazard, occurrence, exposure and etc.
Perfluoropolyesters and fluoropolymers were also mentioned for synthesis
reports. Considering OECD policies, they would like to incorporate alternativesof PFAS for items like food packaging, cosmetics, coatings and varnishes. Thissession also mentioned risk management implementation such as registration7

of chemicals, collaboration with the business sector, increased information
sharing across government and private sector, proprietary and/or voluntary
approaches alongside with regulatory approach. In conclusion, Ms. Leinala
argues that PFAS regulation is the upmost importance to make sure that global
collaboration for PFAS management is done for benefits for citizens and thescientific community.
3. Updates and Recent Activities Related to the US EPA National PFAS Testing
Strategy by Mr. Dawson from EPA (Environmental Protection Agency)
This session mentioned that an important roadmap called the EPA’s
Commitment of Actions 2021-2024 was created by the EPA council for PFAS.
This initiative was created to deal with the PFAS exposure in the United States
to Research, Restrict and Remediate PFAS.
One of the mentioned topics was raising the drinking water standards, this isdue to the prevalence of PFAS in the water system. Another topic mentioned
was the regulation of PFAS.
The initiatives also emphasized on the TSCA (Toxic Substance Control Act)
which is a regulatory framework for data gathering of any PFAS manufactured
since 2011 including pesticides. This data gathering is done by the national
PFAS testing strategy which looks at mixture testing of PFAS and around 90
categories including centroids and other substances. Under TSCA testingorders, it also looks at chemical structure and toxicokinetics.
Also, emerging issues on pesticide packaging was mentioned during thepresentation. It was discovered that active ingredients of pesticides and PFAS
were prevalent in pesticide packaging before the emergence of the EPA council
for PFAS. The creation of this council during the EPA Commitment of Actions
2021-2024 has successfully eliminated 12 PFAS from pesticide packaging. The
council will continue to monitor the situation for pesticide packaging.
The final section of the presentation mentioned conflicting views withstakeholders about PFAS, this is due to the lack of scientific information anddata gathering issue. To combat this, the EPA is planning to create more
publications for supporting scientific evidence and to have webinars andworkshops for further information on PFAS awareness and exposure. For the
EPA, this is an important issue, and it wants to continue to promote theimportance of its strategy in dealing with PFAS exposure in the US.
Mechanisms of Per- and Polyfluorinated Substances Action: PPARɑ and
Beyond Symposium Session
4. Integrating Drug Development Tools to Predict Key Mechanisms of Per- andPolyfluoroalkyl Elimination and Clearance by Dr. Slitt, University of Rhode
Island (Abstract #1039)
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This session mentions that recent data shows that over 200 million people in
the United States rely on tap water that is contaminated by PFAS. In thesession it is mentioned that PFAS comes in all varieties of items such as textiles
used in the Department of Defense, and water system used in the US. PFAS
was also detected in the human liver. The presenter wanted to know which
PFAS were currently present in the human liver.
The session went into detail of the biological process of how PFAS comes into
our body. This includes how PFAS is well absorbed in the GI tract with littlechange of biotransformation, the presenter also mentioned that the liver has thehighest amount of concentration of PFAS. This is likely due to the high binding
affinity for serum albumin which is linked to the detection of liver disease. It wasalso mentioned that it also has tissue binding affinity and reabsorption by renaltransporters which both are used in drug development tools. The session alsomentions Organic Anion Transporter (OAT) and Organic Anion Transporting
Polypeptide (OATP). OAT and OATP play a role in the kidneys which are
involved with bile salts, thyroid hormone and steroid signaling.
With this information, a new form of classification system was created to bringmore transparency of PFAS in the body. It is called the Extended Clearance
Classification Systems (ECCS). This looked at three important points,
Permeability (how much substances it allows to pass through with othercoexisting substances), Ionization (how molecules charge is gained or lostdepending on electrons) and molecular weight (the weight of the substance).
The changes of these points mentioned depend on the metabolism, renal
clearance (Kidney clearance rate) and hepatic uptake which predominantly is
associated with transporters such as OAT and OATP which can be used todetect hepatotoxicity.
In the session, it was also mentioned that PFAS could interfere with OAT
transporters, which could cause a disruption of normal transporters activity inthe liver. This is due to PFAS being an OAT1PB1 inhibitors causing thedisruption of transporters. It was also mentioned that ABCG2 mediatedtransporters, a known multidrug resistance contributor is linked as a substratefor PFAS. These transporters fit to all the categories of the ECCS. It was
mentioned that the ECCS classification system could provide PFAS, PFOS
retention with albumin playing a crucial role. This is due to the system’s ability toidentify transporters and mechanisms which provide useful data for scientists
working on in vivo models.
5. Importance of Evaluating Mode of Action and Human Relevance inAssessment of Human Health Risks of PFAS: Case study with Short-Chain
HFPO-DA by Dr. Heintz, ToxStrategies LLC (Abstract #1040)
It was revealed by the presenter that there was absence of evidence in themode of action of specific endpoints (a direct marker for disease progression) in
humans but recently the EPA has made a toxicity review ofHexafluoropropylene oxide [an organofluorine chemical] (HFPO-DA) as a class9

of PFAS that affects the most sensitive endpoints in mice, which is the liver. This
process is influenced by actions such as apoptosis and hepatotoxicity. It wasalso revealed that HFPO-DA did not bioaccumulate much in mammals. Despite
this, it was shown to have negative effects on rats which saw tumor growth withchronic exposure.
The presenter wanted to know the significance of HFPO-DA on humans. The
presenter has seen the effects of HFPO-DA on PPARα (Peroxisome proliferator
activated receptor alpha) which looked at cell growth pathways, survival of cells,
clonal expansion and liver tumors. The presenter found that PPARα lowered
lipid metabolism regulation, increased in β-oxidation affecting mitochondrial fatty
acids, tumor growth, decreased birth weight and higher mortality rate in birthwere discovered in rodents exposed to HFPO-DA.
It was revealed by the presenter that PPARα in humans has no significant
enrichment process like rodents do. It was also found that this could be due toan enhanced upstream regulator analysis which humans process compared torodents. The presenter also found that humans carry a higher concentration of
PPARα which has less effects for treatments on the human body. Despite thefindings, the author concluded that there was a lack of human relevance basedon current research. The presenter also highlighted the importance of mode ofaction and human relevancies when looking at PFAS toxicities in human healthrisk assessment studies.
6. Is PPARɑ the Molecular Initiating Event Driving Human-Relevant Toxic
Effects of PFAS? By Dr. Schlezinger, Boston University (Abstract #1041)
PPARα (Peroxisome proliferator activated receptor alpha) is a prominent
molecular initiating event that is associated with PFAS-induced toxicity. The
presenter gave an explanation that PFAS exposure was linked to increased LDLcholesterol, CVD and birth weight. This is due to the liver being associated withlipid homeostasis with PPRE (Peroxisome proliferator response elements)
playing a role for gene expression. PFAS can change transcription of lipid
movement in genes thus creating lipidemia due to this change affecting lipid
homeostasis.
A study in mice have indicated that PPARα in males seem to only be affected bylipid regulation disruption, while females are affected by PPARα mechanisms
which did not regulate their lipid homeostasis. This led to the team finding out
the mode of action for the duration of exposure to see any changes in the lipid
accumulation in the liver. This is because the presenter discovered that lipid
homeostasis in the liver depends on exposure time along with sexes and typesof lipids involved in the process.
It was found during this process that PFOAs were not significant in the micestudy unless they undergo treatment manipulation and genotyping for PPARα in
the mice. They have also discovered that PPARα affected females more thanmales in serum cholesterol. The discovery revealed that there was a decreasein HDL levels in males while females have an increased amount of LDL while10not having significant HDL changes. This had led scientists to believe that the
suppression of CYP7a1 (an enzyme for cholesterol) might play a role inaffecting PFOA serum cholesterol in the liver. This led to the conclusion of thepresentation that scientists can finally uncover the complexity of molecularinteractions of PFAS in human relevant toxicity.
7. Mechanisms Linking Mixtures of Per- and Polyfluoroalkyl Substances toIncreased Circulating Cholesterol and Cardiovascular Disease Risk by Dr.
Petriello, Wayne State University (Abstract # 1042)
This session focused on the issues of PFAS affecting cardiovascular disease(CVD) and cholesterol. It is known that atherosclerosis development starts inearly childhood due to apoptosis and reactive oxygen species (ROS). The
biomarkers used for CVD are total cholesterol count, C-reactive protein andTrimethylamine N-oxide (TMAO, an organic compound found in gut microbial
metabolism) and the microbiome. These were looked at for diet manipulation
based on phenotype line of metabolic and high cholesterol studies. To grasp abetter picture, they used a high cholesterol to low fat diet model to use for the
PFAS investigation in mice. PFAS mixtures were measured in mass
spectrometry.
A study from occupational exposure from environmental exposure of PFAS from
West Virginia found that there was an increase of cholesterol in residents livingin the exposed occupational area. When PFAS were investigated in mice, theyfound that they had an increase in overall cholesterol and bile acids. They havealso found that TNF-α (Tumor Necrosis Factor alpha) is a cytokine responsiblefor immune cell response and IL-6 (Interleukin-6) found in female mice.
The study also found that PFOS showed the strongest sign of affecting
cholesterol over other PFAS groups. In the study of mice, they also found that
PFAS mixtures likely reduced endogens cholesterol formation as well as
decrease bile acid excretion. It is also understood that PFAS mixtures increased
the amount of bile acid transporters despite the decrease of excretion of bile
acids. This led to the question that despite having some indication of PFAS
mixtures affecting the bile, the presenter emphasized that PFAS studies on theintestines are still understudied and should be investigated.
Looking at the absorption and excretions of PFAS and cholesterol, it was
revealed that the ABST inhibitor (used for non-alcoholic fatty liver disease
treatment) is positively associated with decrease of PFAS toxicity related tocholesterol. It is also revealed that PFAS mixtures modulated genes related tocholesterol role of absorption and excretion. This also influences the
microbiome which controls sterol homeostasis and impact secondary bile acids
produced from bacteria. The presenter concludes that a multi-omics approach
could allow scientists to identify mechanisms of cholesterol and bile acidcirculation to find a link between PFAS and atherosclerosis risk.

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8. Alternate Mechanisms of PFAS Toxicity by Dr. Apte, University of Kansas
Medical Center (Abstract #1043)
HNF4α (Hepatocyte nuclear factor 4-alpha) is a master regulator of hepaticdifferentiation as well as responsible for metabolism regulation and proliferationof liver and intestinal epithelial cells. The presenter states that HNF4α showeddegradation with interaction of PFAS and PFOAs. The degradation of HNF4α isshown to affect drug metabolism, coagulation factors, nutrient metabolism, bile
acid synthesis as well as transport and no cell deaths.
The presenter then mentioned that stability in proteins of fatty acid binding was
linked with HNF4α which resulted in steatosis (excess fat buildup of liver cells).
The presenter also found that this type of activity can be seen when myristic
acid and PFOA interact with HNF4α. This led to the discovery that DNA
response elements like protein-binding sites are induced by PFAS exposure
which affects the circadian rhythm of mice. Overall, the presenter wanted toshow that new hypotheses needed to be considered when dealing withmechanisms of PFAS toxicity.

IV. Neurotoxicology
Symposium Session: The State of the Science Linking Environmental
Chemicals to Age-Related Neurocognitive Disease
1. The Effects of Chronic Exposure to Ambient Traffic-Related Air Pollution on
Alzheimer’s Disease Phenotypes in Wildtype and Genetically Predisposed
Male and Female Rats by Dr. Lein from University of California Davis(Abstract #1123)
The presenter introduced to the audience that in epidemiological studies,
Alzheimer disease (AD) and TRAP (Traffic-Related Air Pollution) have a stronglink to one another. The presenter explained that AD from genetic factors wasless than 5% and underlying factor of the disease might come fromenvironmental factors, lifestyle or other disease related factors. The presenter
advocated the implementation of effective public health policies to reduce theprevalence of AD. Further details of TRAP mechanism, the identification offactors and chronic exposures of AD were presented. The presenter created anexperiment with rats of exposure chambers in real time with control of filteredair.
The experiment revealed that TRAP increased inflammatory response and rat
data on neuroinflammation was closely related to human AD pathology. The
data has also shown that women tend to have AD more than men. It was also
revealed that TRAP guidelines tested were within guidelines of WHO and the
EPA limits for PM2.5. During the experiment, they found plaque formation on
the hippocampus of rats exposed to TRAP compared to rats in an air filteredenvironment. It is also found that rats have increased pTau (biomarker protein in
the CNS for AD) in male rats and found exacerbated neural cell loss in 1512

month-old rats which is approximately 45 years old in humans. The experimenthas also found that Aβ42 (amyloid beta 42) a biomarker for AD has toxic effects
on AD when the rats are in an exposed TRAP environment, Aβ42:40 ratio
balance is essential for cortical reproduction. There is also evidence that TRAP
promotes cognitive deficits in male rats when it comes to learning and memory.
This might be due to refractive particles being present in the hippocampus of
the brain. The experiment also has found fewer refractive particles in otherregions of the brain in TRAP-exposed animals.
The presenter has concluded that the standards of PM2.5 and other TRAPrelated measures are not sufficient for protection of the aging brain.
2. Uncovering the Complex Relationships between Air Pollution, Social
Determinants of Health, and Aging by Dr. Ward-Caviness from US EPA(Abstract #1125)
The presenter showed air pollution and SDoH (Social determinants of Health)
as a growing environmental issue for the EPA. The presenter showed data ofadjusted hazard ratio, which looks at hazards related to the environment andsocial deprivations. An example given was the difference between air mixturesin high and low social classes. This led to a topic of having clean air solution tohave more of an impact on low social deprivation communities than higher
social classes. The presenter then showed data showing epigenetic aging
based on DNA methylation analysis such as the biomarker Age Acceleration
Difference (AAD) to compare between social classes.
The EPA also looked at neighborhood quality indicators such as street
cleanliness, graffiti and greenspace. It was shown that neighborhood quality
was significantly associated with epigenetic aging biomarkers like AAD. It wasalso shown that increase in greenspace like tree count has shown positiveeffects on slowing down AAD. The reason for the positive effect is still not
known. A mice study conducted by EPA has shown that housing depletion has
been associated with depleting body fat percentage based on housing
condition. Low housing conditions have shown that there was an increase ofhigh fat, higher LDL cholesterol and plasma glucose. While high housing
conditions has shown lower fat percentage than the low housing counterpart.
The study has also shown that short term exposure has shown that no
significant epigenetic aging. Another concern is that EPA has found that air
pollution and dementia has been linked with the social environment.
Symposium Session: Neuroinflammation as a Central Mediator of
Neurotoxicity: Implications for Environmental Links to Chronic
Neurodegenerative Diseases
3. NLRP3 Inflammasome Function in the Response to Parkinson’s-AssociatedPesticides by Dr. Havrda from Dartmouth College (Abstract #1080)

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NLRP3 is an important innate immune system protein that is responsible forresponding to microbial infections and cell damage in the human body. When it
is active in the body, it becomes an inflammasome which can have negative
effects. The effects can include ROS (Reactive Oxidative Stress), cell death,mitochondrial dysfunction due to genetic mutation by environmental exposure,misfolded protein and lysosome dysfunction which can lead to negative
outcomes. In animal studies, it is found that NLRP3 can have positive effects
such as protection from neuron loss. This experiment was done by looking at
specific NLRP3 mouse models. They found that exposure to rotenone (a fishpiscicide) led to neurotoxicity in mice with signs of neurodegeneration andcognitive dysfunction. Measure of NLRP3 can be indicated by blood test looking
at haptoglobin levels.
The importance of NLRP3 being responsible for Parkinson’s disease being
linked to pesticides is an issue that is present today. The mechanism of NLRP3
and other immune system responses should give scientists a better
understanding of the mechanisms involved in Parkinson’s-associate pesticides
for the development of therapeutic methods and diagnostic testing.
4. Innate Immune Responses to Alpha-Synuclein Facilitate Its Aggregation in
Parkinson’s Disease by Dr. Panicker from Cleveland Clinic Lener ResearchInstitute (Abstract #1082)
The presenter started with a basic information regarding Parkinson’s disease(PD) which is associated with dopamine neuron death. PD is the fastest
growing neurological disorder and treatment for PD consists of dopamine
antagonist.
An important protein called α-syn (alpha synuclein) plays a crucial role forregulating neurotransmission and trafficking. It is thought that the pathogenesisof PD derives from α-syn dysfunction. The presenter tested an α-syn PreFormed Fibrils (PFFs) model which was injected in the mice’s brain to induce αsyn aggression. This led to Lewy body holes which led to the death of dopamine
neuron, causing PD. It is found that microglia (non-neuro cells in the CNS)
mediated inflammatory response were seen in the development of PD. It wasalso found that inflammasomes from microglia are present in human cells andwere associated with misfolded proteins which are supported with α-syninteractions. The interactions occurred by having the inflammasome like NLRP3
being active in the brain caused the secretion of IL-1β which is a known
neurotoxic inducing interleukin.
The presenter concluded that the combination of NLRP3 and α-syn wereinterlinked together for the implication of PD development. More studies areneeded to further understand the mechanisms behind this process to help reachthe underlying cause of action and to help scientists with diagnostic andtherapeutic solutions for PD.

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5. Extracellular Vesicles as Biomarkers and Mechanistic Mediators of Aging and
Age-Related Neurodegenerative Diseases by Dr. Lu from Harvard University(Abstract #1122)
The presenter has shown his research in Extracellular Vesicles (EV) being used
as a biomarker and functional mediator for environmental and disease research,
this is due to the large amounts of EV’s circulating in bodily fluids. It was also
explained that EV heterogeneity found difficulty of tissue of organs andsubtypes such as biogenesis and composition. It was also revealed that EVs
from a mouse brain revealed that by using proteomics, it was found that EVs
contain plasma membranes for proteins. It was revealed by an EV subtype
called ARMMs linked protein which were associated with increase expression ofstem cell differentiation. It was also mentioned that EV neural progenitor cells in
metals are linked with ARMMs. Cadmium and arsenic inhibition of ARMMs andleads to an increase in both cadmium and arsenic toxicity due to not being able
to digest cadmium and arsenic properly. It was also discovered that the transfer
of antioxidant proteins could have protective effect of ARMMs in cadmium
neurotoxicity. The author concluded that novel EV pathways and signatures
could explore a new way for potential biomarkers and functional systems which
can lead to more discovery in neurodegenerative research based on theenvironment.

V.

Emerging issues

Hot Topic Session: Where the Rubber Meets the Road: Impact of Tire Wear
Particles on the Environment and Human Health
1. 6PPD-Quinone and Beyond: Tire Rubber Additives and Transformation
Products as Emerging Contaminants by Dr. Tian from Northwestern
University
The presenter started the presentation with the death of coho salmon innorthwestern US. Storms that carry 6PPD chemicals are dipped in the river
where coho salmons thrive and then experience Urban Runoff Mortality
Syndromes (URMS). The increased death of the salmons is due to not only the
specificity of 6PPD chemicals but also the rise of urbanization and traffic
intensity, which 6PPD chemicals are associated due tire use. The study wasable to create a non-targeted analysis which could detect contaminants without
identifying every chemical. This was done by tracking chemical signatures fromcollected water containing 6PPD chemicals which track specific chemicalsignature for both treatment and contamination sources.
A method called effect directed analysis was created to link observed toxicity
with non-target pollutants. They use tire wear leachate which looked at toxic
chemicals for use of mass spectrometry for identifying and following HPLC
which found the only chemical which linked to coho salmon death. It was
discovered that an unknown chemical (C18H22N2O2) which has an
appearance of a purified pink-magenta solid. The scientists were able to15

rearrange the unknown chemical to a known chemical with similar
characteristics, what they discovered was 6PPD. The scientists were also torearrange the 6PPD further using Nuclear Magnetic Resonance techniquewhich led to the creation of 6PPD-Quinone, which was shown to be more toxic
and affecting larger variety of fish such as rainbow trout.
The mechanism of 6PPD has shown cerebrovascular effect linked to leak blood
brain barrier, O- glucuronide metabolites. It was also observed that not highsoluble along with being moderately hydrophobic and has similar sorption
properties with other plastics. Since 6PPD is found in water, there is a highchance that it is susceptible to human toxicity. In zebrafish testing, it has beenfound to decrease head size and facial deformation. In conclusion, they havefound that short term acute exposure of tire wear particles showed signs ofhyperactivity. An increase in exposure, the scientists have found that there wasincrease of motor activity in zebrafish. The reason for the hyperactivity was dueto the ion chamber modulation when interacting with tire wear particles. The
presenter concluded that more studies on tire wear particles needed to be done
to find other potential unknown chemicals which could cause biological harm to
the environment and people.
2. Coordinating to Fill Critical Knowledge Gaps on the Tire Anti-DegradantContaminant of Emerging Concern 6PPD-Quinone by Guiseppi-Elie from US
EPA
The presenter made an introduction concerning of 6PPD-Quinone emergencein the US. It was discovered that accumulation of 6PPD comes from storms,
which were collected for water treatment for finding 6PPD chemicals. The riseof chemicals in the US found that tire manufacturers are competing for making
innovative chemicals for tire use. This has led to the US EPA creating a crosscoordination of other agencies to investigate 6PPD chemicals. The presenter
introduced an initiative called the Office of Research and Development (ORD)
StRAP, a strategic research planning project for 2023-2026 with six national
research programs into the investigation of environmental health with input from
EPA partners. The presenter concluded that 6PPD along with other chemicals of
unknown origins should always be monitored on a multi-organizational level tomake sure that it can quickly detect and research potential health risks it poses
to humans and the environment.

VI.

Microbiology

SOT/EUROTOX Debate: Can the Microbiome Mediate the Toxicity ofEnvironmental Chemicals? Presented by Dr. Tamala Tal from the Helmholtz
Centre for Environmental Research, Germany and Dr. Karsten Beekmann from
Wageningen University, the Netherlands
The SOT representative, Dr. Tamala Tal started the debate by introducing
ingested xenobiotics like additives, pesticides, drugs make their first contact16

with the gut microbiome which affects the biological half-life of xenobiotics. An
argument made was that chemical exposure can alter the microbiome which
can be influenced by over 124 chemicals. It was also found that chemical
selected microbiomes have shown altered function in toxicokinetic properties. It
was also mentioned that around 2/3 are bio transformed by microorganisms.
This interaction in the microbiome affects the structural activity of therelationship between microorganisms in the microbiome. This leads to altered
toxicodynamics, this results in microbe dependent drug interaction which cancause dose limiting in the GI (Gastrointestinal) tract toxicity. An example of thiswas the drug called Irinotecan which is a drug used to treat colon and rectum
cancer. The drug is primarily in the gut lumen, which as a result has a drug
limiting toxicity which might not be as effective at targeting the intended
molecular drug target.
Dr. Karsten Beekmann, a representative for Eurotox, has argued that exposureof microorganisms is not predictive of composition due to differences between
composition (biological material) and function not always aligning one another.
The presenter explained that there are over trillions of bacteria which introducesof thousands of possibilities for interactions which we could not follow. It wasalso explained that there is a difference of epithelial gut microbiota for eachindividual person, thus not all microbiome focused targets can be reached topeople. It was also mentioned that stressors and microbe space are also
different between people. This causes a difference in environmental chemicaldifferences among individuals. Dysbiosis association was also mentioned which
is linked to disease in people. It was also argued that it would take many years
to understand the microbiome due to the amount present in the human bodywhich also includes other living organisms with the microbiome. The presenter
concluded that risk, hazards, correlation vs causation and limited understanding
persists in research thus argues that microbiome cannot exhibit toxicity ofenvironmental chemicals.
Dr. Tal has argued that Microbial Associated Genomics can show examples ofbad microbe environments such as salmonella having a negative correlation
with the human microbiome. The presenter also agreed that the microbiome is
too complicated to study with examples such as model systems. Human
Associate Microbiomes are microbes that can be cultured for research which
can be used for not only humans but also with other living organisms like bees
and zebrafish. Dr. Beekmann had argued the models of study and individual
differences, methods and challenges of limited understanding make it difficult togain an understanding of environmental chemicals and microbiome interactions.
Dr. Tal had argued that microbiome is not only present in the gut but also theskin and lungs which has a potential to explore the bigger potential of
microbiome research. Also, it was concluded that differences in ecosystemchange can have a potential to affect the microbiome environment in not only
humans but other organisms in the ecosystem.

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VII. Risk Assessment
SOT/EUROTOX Roundtable: Is Mixture Risk Assessment Now Established
Regulatory Practice? Introduced by Dr. Rider from NIEHS
The session’s aim was to assess human health risk when it comes to combined
exposures of mixtures. International bodies including WHO, OECD, US EPA,EFSA and ECHA have made attempts to work together to implement a way tohave evidence-based risk assessments to exposures to chemical mixtures
which can come from the environment or food. The current situation ofassessment is inconsistent and where it is mandated, it is often very restrictive
due to requirements of scenarios and chemical groups. Recently, the European
Commission’s new initiative the “Chemicals Strategy for Sustainability Towards
a Toxic-Free environment” has gained attraction of debate whether there is an
unrecognized issue regarding health effects in human populations of exposure
to mixtures. The session’s mains focus is on regulatory toxicologist which
present mixture risk assessment and address the problem whether establishedregulatory practice across regulatory domains.
1. The first presenter of the day was Dr. Herzler, who works for the German
Federal Institute for Risk Assessment (BfR).
The aim of the topic was to give an overview of US and Europe but also
introduce the German regulatory system done at the federal level. There is adifference in naming when it comes to mixture assessments. In the US, thepreferred name of mixtures is combined mixtures which looks at a mixture thathas two or more substances which each substance retains its own chemical
identity. In Europe, the term “Intentional mixtures” is used to address chemical
mixtures which look at “Well-Defined substances”. The “Well-Defined
substances” is the definition which can identify well known chemicalcompositions and properties. Another is the definition of Unknown or Variable
Composition, Complex Reaction Products, or Biological Materials (UVCBs), thislooks at unknown mixtures and tries to characterize and identify the mixture. To
further analyze these compounds, a Mixture Assessment Factor (MAF) is used
to test mixtures of industrial chemicals in the EU’s Chemicals Strategy for
Sustainability. The final definition is Environmental Risk Assessment whichlooks at pesticides and background concentrations of substances based on thelife cycle of a given environment.
In German federal standards of assessment, they look at three importantprinciples which rely on health risk exposure assessment. They look at the
proportionality principle, which looks at the fairness and justice of restrictions
imposed by a measure, acts and good that can be achieved for chemicals. The
German government also focuses on common toxicological targets, which looks
at chemical-based toxicity which have physicochemical characteristics of a
mixtures affecting cellular or metabolic pathways. Off target assessment looks
at targets on other biological species or the environment. The final principle is18the chemical viability for systemic uptake. This principle looks at a substancethat is absorbed into a living system made of physiological activity. Even withthese stated principles, it still has its limitations. One of the mentioned
limitations where human biomonitoring, which is not stated in any of theprinciples, this is due to not having a clear specificity on humans’ assessment ofchemicals. The presenter concluded that this leads difficulty of exposure
assessment in relation to human health due to the guidelines not being clear of
having a definitive principle when looking at human health specifically.
2. Presenter Dr. Wilks from the University of Basel.
He presented the EFSA (European Food Safety Authority) which is an EU
agency which focuses on scientific evidence on food systems across Europe.
The main principles presented at EFSA were the Cumulative Assessment
Groups (CAGs) which have four levels to identify compounds that exhibit
toxicological properties in a system or organ. Level 1 of CAGs looks at the
toxicological target of an organ or system which assess what mixtures orcompounds are specifically targeted in the living organism. Followed by thisLevel 2 focuses on the phenomenological effect of the mixture which looks atwhether the effects of the mixtures are toxic, neutral or beneficial to a living
system. Level 3 focuses on the mode of action which primarily looks for a
mixture which can have functional or anatomical changes in the living organism.
The final level that is assessed is the mechanism of action, which looks at the
specific biochemical interactions which a substance or mixture can produce aneffect. This final level looks at molecular targets, enzymes and receptors thatwould interact with the given mixture or substance. EFSA has a separate
cumulative exposure assessment which is done by primarily by a software
called SAS which is a standardized statistical program. This leads to the final
assessment of risk characterization which quantifies the exposures and toxicityof the given mixture. The presentation concludes that there is an action plan
initiative between the EFSA and the EC (European Commission) for pesticide
residues regulation and control by the year 2030.
3. Presenter Dr. Matheson by US Consumer Product Safety Commission
The aim of this presentation was to look at medical products which have links tosubstances or mixtures which are risk assessed at the commission. The
Chronic Hazard Advisory Panel (CHAP) was established to look at risk
associated with consumer products which focused on phthalates. The methodof assessment is the analysis of phthalate exposure and risk this possesses for
women of reproductive aging using NHANES and SFF for children which arebiomonitoring data from the CDC of National Report on Human Exposure to
Environmental Chemicals. The presenter concluded that more focus is neededin product safety of chemicals to find out more risk assessments when it
pertains to human health exposure to mixtures.

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It’s Not Easy Being Green: Applying Alternatives Assessment to Create
Safer Consumer Products
4. Development and Implementation of the National Academies Framework to
Guide Selection of Chemical Alternatives by Dr. Dorman from North Carolina
State University (Abstract #1157)
This session focused on chemical alternative assessments which weredeveloped to identify chemicals that are most likely to harm human andecological health, and to provide a framework which the industry can develop
and adopt safer alternatives. The framework starts with the science policy field
which discusses the matter for adaptation. This is then followed by looking for achemical of particular concern and summarizing the unintended consequences.
The current assessment of chemical alternative assessments does not consider
cost, performance, human health or environmental health. The presentersuggested a framework which can be broken down into three categories which
are: A (unacceptable alternative), B (preferred alternative) and C (acceptable
alternative). This framework was assessed by National Academies of Sciences,
Engineering, and Medicine (NASEM) which looked at the function andperformance requirements for the framework initiative.
The presenter also stated that we must consider the life cycle thinking of
possible impacts of a chemical at all stages. This includes production, use,
performance, economic and disposal assessments. This can include tradeoff
risks in chemicals such as product functionality, efficiency, process safety andresources which need to be considered for the framework initiative. Casestudies include computational and mechanistic data from the chemicalalternative assessment. The presenter concluded that the framework needs tobe implemented more in the industry to not only help understanding of chemical
products but also the health of humans and the environment must be
considered, when using alternative chemicals in production.

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