Higher ethylene oxide (EtO) exposure is significantly associated with an increased risk of stroke in U.S. adults, particularly those under 50 years old.
Highlights:
- Higher levels of EtO are linked to increased stroke rates, with individuals in the top 25% of exposure showing a stroke prevalence 1.6 times higher than those in the bottom 25%.
- The association between EtO and stroke is particularly significant in adults under 50 years, with an OR of 1.94, indicating a nearly doubled risk.
- No significant association was found between EtO exposure and stroke in adults aged 50 and above.
- The positive relationship between EtO levels and stroke was consistent across all demographic subgroups except age.
Source: Frontiers in Aging Neuroscience (2024)
What is Ethylene Oxide?
Ethylene oxide (EtO) is a highly reactive organic compound widely used in industrial applications.
It is a key ingredient in the production of various chemicals, such as ethylene glycol, synthetic detergents, plastics, and antifreeze.
EtO is also employed as a sterilizing agent for medical equipment and supplies due to its effective bactericidal properties.
Common routes of exposure
- Industrial Emissions: Workers in factories and plants that manufacture or use EtO can be exposed through inhalation and skin contact.
- Medical Sterilization: Healthcare workers and individuals in facilities that sterilize medical devices are at risk of EtO exposure.
- Automobile Exhaust and Air Pollution: People living in urban areas or near industrial zones can be exposed to EtO present in polluted air and automobile exhaust.
- Tobacco Smoke: Both smokers and those exposed to secondhand smoke can absorb EtO.
- Consumer Products: Some household and personal care products may contain EtO as a contaminant.
Effects Within the Body
Upon exposure, EtO can be absorbed through the respiratory tract and skin, distributing throughout the body.
It reacts with proteins in the blood to form hemoglobin adducts (HbEtO), which serve as biomarkers of exposure.
EtO can induce oxidative stress and inflammation, damage endothelial cells, and increase vascular stiffness.
These effects contribute to cardiovascular issues, including hypertension and an elevated risk of stroke.
Elimination Half-Life
The biological half-life of EtO is relatively short, approximately 42 minutes.
However, when it reacts with hemoglobin to form HbEtO, the half-life extends to about 4 months.
This longer half-life of HbEtO allows for the detection and measurement of EtO exposure over a more extended period.
Major Findings: Ethylene Oxide (EtO) Exposure vs. Stroke Risk (2024)
1. Higher EtO Exposure Linked to Increased Stroke Rates
The study found that higher levels of ethylene oxide (EtO) in the body were associated with a higher risk of having a stroke.
Specifically, people with the highest levels of EtO exposure had a stroke prevalence that was 1.6 times higher than those with the lowest levels of exposure.
This was determined using statistical models that accounted for various factors, ensuring that the link between EtO and stroke was not due to random chance or other variables.
2. Significant Impact on Young Adults
The association between EtO exposure and stroke was especially pronounced in adults under 50 years old.
In this age group, higher EtO levels were associated with a nearly doubled risk of stroke (OR=1.94).
This suggests that younger adults who are exposed to higher levels of EtO are at a significantly higher risk of experiencing a stroke compared to their peers with lower EtO exposure.
3. No Significant Association in Older Adults
For adults aged 50 and above, the study did not find a significant link between EtO exposure and stroke risk (OR=0.97).
This indicates that while EtO exposure is a notable risk factor for stroke in younger individuals, its impact is not as clear in older adults.
This could be due to the presence of multiple other risk factors for stroke in older age groups that may overshadow the effects of EtO.
4. Consistency Across Demographic Subgroups
The study’s findings were consistent across various demographic subgroups, such as gender, education level, marital status, and BMI.
This means that the increased risk of stroke associated with higher EtO exposure was observed regardless of these different factors.
This consistency strengthens the validity of the results, indicating that the association between EtO and stroke is robust across diverse population groups.
5. Need for Environmental Policies & Awareness
Given the significant association between EtO exposure and stroke risk, particularly among younger adults, the study highlights the urgent need for policies aimed at reducing EtO pollution.
It also underscores the importance of raising public awareness about the potential health risks associated with environmental pollutants like EtO.
Reducing exposure to EtO could be an important step in preventing strokes, especially in younger populations.
Study Overview: Ethylene Oxide & Stroke Risk in Young Adults (2024)
The study by Lingying Le et al. examined the association between ethylene oxide (EtO) exposure and stroke among U.S. adults using data from the 2013–2018 National Health and Nutrition Examination Survey (NHANES).
Sample
- The study included 5,071 participants from NHANES 2013-2018 data.
- Participants were non-institutionalized U.S. residents.
- After excluding individuals with missing data on hemoglobin adducts of ethylene oxide (HbEtO) and stroke, as well as those with missing covariates, the final sample size was 5,071.
Methods
- Measurement of EtO Exposure: EtO levels were measured using hemoglobin adducts (HbEtO), a biomarker for EtO exposure, detected through high-performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS).
- Stroke Assessment: Stroke diagnosis was based on self-reported responses to a medical conditions questionnaire.
- Covariates: Included gender, age, race/ethnicity, education level, marital status, BMI, LDL-C, hypertension, diabetes, and cancer history.
- Statistical Analysis: Multifactorial logistic regression models were used to analyze the data. Smoothed curve fitting validated the findings. Subgroup analysis and interaction assessments were performed to evaluate robustness.
Limitations
- Cross-Sectional Design: The study’s cross-sectional nature prevents the determination of causality between EtO exposure and stroke.
- Biomarker Limitations: The study relied on HbEtO levels as a biomarker, which may not capture all aspects of EtO exposure.
- Self-Reported Data: Stroke diagnoses were based on self-reported information, which may introduce recall bias or misclassification.
- Confounding Factors: Despite adjusting for many covariates, potential residual confounding cannot be completely ruled out.
- Lack of Stroke Subtype Differentiation: The study did not distinguish between different stroke subtypes, limiting the specificity of the findings.
How Ethylene Oxide (EtO) May Increase Stroke Risk in Young Adults
Increased Occupational & Environmental Exposure
Young adults, aged 20-50 years, are typically more active in the workforce and may be exposed to EtO through various occupational settings, such as industrial plants, healthcare facilities, and agricultural environments.
This age group is also more likely to engage in social activities that increase exposure to environmental pollutants, such as automobile exhaust and tobacco smoke.
The higher levels of exposure to EtO in their daily environments could significantly elevate their stroke risk.
Oxidative Stress & Inflammation
EtO exposure can lead to oxidative stress, which results from the overproduction of reactive oxygen species (ROS).
This oxidative stress can damage vascular endothelial cells, leading to inflammation and the formation of atherosclerotic plaques.
Inflammatory responses further contribute to vascular damage and increase the likelihood of blood clot formation, a key risk factor for stroke.
Endothelial Dysfunction
EtO has been shown to cause endothelial dysfunction, impairing the normal function of the cells that line blood vessels.
This dysfunction affects vascular tone and blood flow regulation, increasing vascular stiffness.
Such changes in the vascular system can impair cerebral blood flow regulation, making young adults more susceptible to strokes.
Platelet Aggregation & Thrombosis
Exposure to EtO can increase platelet aggregation and the expression of coagulation factors, promoting blood clot formation.
Young adults exposed to higher levels of EtO may experience increased thrombosis risk, contributing to a higher incidence of stroke.
Metabolic Factors
Young adults have more robust metabolic functions in the liver and kidneys, leading to more active processing and clearance of EtO.
The metabolic processes can produce higher levels of ROS and free radicals, which cause oxidative damage and inflammation, indirectly increasing stroke risk.
Possible Reasons Ethylene Oxide Didn’t Appear to Increase Stroke Risk in Older Adults
Prevalence of Other Risk Factors
Older adults typically have a higher prevalence of other established stroke risk factors, such as hypertension, diabetes, and cardiovascular diseases.
These existing conditions can overshadow the impact of EtO exposure on stroke risk.
The contribution of EtO to stroke risk might be relatively minor compared to these dominant factors in older populations.
Physiological Changes with Aging
As individuals age, their bodies undergo various physiological changes, including vascular aging.
Older adults tend to have increased vascular stiffness, collagen deposition, and elastin fiber breaks.
These age-related changes might alter the sensitivity of blood vessels to the effects of EtO, reducing its impact on stroke risk.
Reduced Sensitivity to Oxidative Stress
Younger adults’ vascular endothelial cells may be more sensitive to oxidative stress and inflammatory responses induced by EtO exposure.
In contrast, older adults might have a reduced sensitivity to these effects due to long-term exposure to various environmental and physiological stressors over their lifetime.
This reduced sensitivity could result in a diminished impact of EtO on stroke risk in older populations.
Cumulative Lifetime Exposure
Over a lifetime, older adults have been exposed to a variety of environmental toxins and pollutants.
The cumulative effect of these exposures might lead to adaptive changes in the body that mitigate the impact of additional EtO exposure.
In contrast, younger adults, with relatively less cumulative exposure, might experience a more pronounced effect from EtO.
Masked Effects
In older adults, the impact of EtO exposure on stroke risk might be masked by the more prominent effects of other risk factors and comorbidities.
As a result, any potential association between EtO and stroke may not be as detectable in this age group compared to younger adults.
Conclusion: Ethylene Oxide & Stroke Risk in Young Adults
This study found a significant association between ethylene oxide (EtO) exposure and an increased risk of stroke, particularly among U.S. adults under 50 years of age.
The findings suggest that higher levels of EtO, a common industrial and environmental pollutant, may contribute to stroke incidence in younger populations.
Despite the robust methodology and large sample size, the study’s cross-sectional design limits the ability to establish causality.
Further longitudinal research is needed to confirm these findings and to explore the underlying biological mechanisms.
These results underscore the importance of developing and implementing policies to reduce EtO emissions and raising public awareness about the health risks associated with EtO exposure.
Addressing these environmental risk factors could play a crucial role in stroke prevention, especially for younger adults.
References
- Study: Positive association of ethylene oxide levels with young stroke: a population-based study (2024)
- Authors: Lingying Le et al.
