Heat or Burn? Impacts of Intrauterine Tobacco Smoke and E-Cigarette Vapor Exposure on the Offspring's Health Outcome

E-Cigarettes and Associated Health Risks: An Update on Cancer Potential

The potential cancer risk associated with electronic-cigarette (e-cigarette) use is ongoing and remains a subject of debate. E-Cigarettes work by heating a liquid that usually contains nicotine, flavorings, and other chemicals. When the liquid is heated, users inhale an aerosol into their lungs. While e-cigarettes are generally considered less harmful than traditional tobacco products, they still contain potentially harmful chemicals, which can damage DNA and lead to cancer. Several studies have investigated the potential cancer risk associated with e-cigarette use, while other studies have suggested that e-cigarette aerosol may contain carcinogenic chemicals that could increase the risk of lung and bladder cancer in humans. However, these studies are limited in their scope and do not provide conclusive evidence. Overall, the long-term cancer risk associated with e-cigarette use remains uncertain, more research is needed to fully understand the potential risks and benefits of e-cigarettes. However, this review will allow the investigator to get more recent updates about e-cigarettes.

[Pregnant women's use of tobacco and electronic cigarettes: A cross sectional survey]

OBJECTIVES

The article aims to describe tobacco and e-cigarette use among pregnant women: estimate the prevalence, identify the determinants and motivations of these behaviours.

METHODS

Cross-sectional, multicentre, descriptive observational study using self-administered questionnaires for pregnant women who visited ELENA healthcare centers in May 2021.

RESULTS

Of 223 patients, 38% were smokers before pregnancy and 16% continued to smoke during pregnancy. Nearly all the smokers (98%) declared that they had reduced or stopped their tobacco use, mostly without help. Young age, lack of professional activity, an unfavourable reaction to the announcement of the pregnancy, heavy smoking before the pregnancy and the presence of a smoker spouse were associated with smoking during pregnancy. Our study identified 10% of vapers before pregnancy and 7.2% during pregnancy. Of those who vaped during pregnancy, 81% were smokers before pregnancy. Most of them used a nicotine containing liquid and 38% of vapers combined smoking and e-cigarettes during pregnancy. There was no association between vaping during pregnancy and smoking cessation. A minority of women had received information about smoking during pregnancy.

CONCLUSIONS

The use of electronic cigarettes by pregnant women is a poorly-known reality in France, yet it concerns approximately 7% of the women in our sample. Prospective studies on larger numbers are needed to assess the prevalence of vaping among French pregnant women and its evolution during pregnancy.

Effect of E-Vaping on Kidney Health in Mice Consuming a High-Fat Diet

High-fat diet (HFD) consumption and tobacco smoking are risk factors for chronic kidney disease. E-cigarettes have gained significant popularity among younger populations worldwide, especially among overweight individuals. It is unclear whether vaping interacts with HFD consumption to impact renal health. In this study, Balb/c mice (male, 7 weeks old) were fed a pellet HFD (43% fat, 20 kJ/g) for 16 weeks when exposed to nicotine or nicotine-free e-vapour from weeks 11 to 16. While HFD alone increased collagen Ia and IV depositions, it did not cause significant oxidative stress and inflammatory responses in the kidney itself. On the other hand, e-vapour exposure alone increased oxidative stress and damaged DNA and mitochondrial oxidative phosphorylation complexes without significant impact on fibrotic markers. However, the combination of nicotine e-vapour and HFD increased inflammatory responses, oxidative stress-induced DNA injury, and pro-fibrotic markers, suggesting accelerated development of renal pathology. Nicotine-free e-vapour exposure and HFD consumption suppressed the production of mitochondrial OXPHOS complexes and extracellular matrix protein deposition, which may cause structural instability that can interrupt normal kidney function in the future. In conclusion, our study demonstrated that a HFD combined with e-cigarette vapour exposure, especially when containing nicotine, can increase susceptibility to kidney disease.

Advances in respiratory physiology in mouse models of experimental asthma

Recent advances in mouse models of experimental asthma coupled with vast improvements in systems that assess respiratory physiology have considerably increased the accuracy and human relevance of the outputs from these studies. In fact, these models have become important pre-clinical testing platforms with proven value and their capacity to be rapidly adapted to interrogate emerging clinical concepts, including the recent discovery of different asthma phenotypes and endotypes, has accelerated the discovery of disease-causing mechanisms and increased our understanding of asthma pathogenesis and the associated effects on lung physiology. In this review, we discuss key distinctions in respiratory physiology between asthma and severe asthma, including the magnitude of airway hyperresponsiveness and recently discovered disease drivers that underpin this phenomenon such as structural changes, airway remodeling, airway smooth muscle hypertrophy, altered airway smooth muscle calcium signaling, and inflammation. We also explore state-of-the-art mouse lung function measurement techniques that accurately recapitulate the human scenario as well as recent advances in precision cut lung slices and cell culture systems. Furthermore, we consider how these techniques have been applied to recently developed mouse models of asthma, severe asthma, and asthma-chronic obstructive pulmonary disease overlap, to examine the effects of clinically relevant exposures (including ovalbumin, house dust mite antigen in the absence or presence of cigarette smoke, cockroach allergen, pollen, and respiratory microbes) and to increase our understanding of lung physiology in these diseases and identify new therapeutic targets. Lastly, we focus on recent studies that examine the effects of diet on asthma outcomes, including high fat diet and asthma, low iron diet during pregnancy and predisposition to asthma development in offspring, and environmental exposures on asthma outcomes. We conclude our review with a discussion of new clinical concepts in asthma and severe asthma that warrant investigation and how we could utilize mouse models and advanced lung physiology measurement systems to identify factors and mechanisms with potential for therapeutic targeting.

In Utero Exposure to Maternal Electronic Nicotine Delivery System use Demonstrate Alterations to Craniofacial Development

OBJECTIVE

Develop a model for the study of Electronic Nicotine Device (ENDS) exposure on craniofacial development.

DESIGN

Experimental preclinical design followed as pregnant murine dams were randomized and exposed to filtered air exposure, carrier exposure consisting of 50% volume of propylene glycol and vegetable glycine (ENDS Carrier) respectively, or carrier exposure with 20 mg/ml of nicotine added to the liquid vaporizer (ENDS carrier with nicotine).

SETTING

Preclinical murine model exposure using the SciReq exposure system.

PARTICIPANTS

C57BL6 adult 8 week old female pregnant mice and exposed in utero litters.

INTERVENTIONS

Exposure to control filtered air, ENDS carrier or ENDS carrier with nicotine added throughout gestation at 1 puff/minute, 4 h/day, five days a week.

MAIN OUTCOME MEASURES

Cephalometric measures of post-natal day 15 pups born as exposed litters.

RESULTS

Data suggests alterations to several facial morphology parameters in the developing offspring, suggesting electronic nicotine device systems may alter facial growth if used during pregnancy.

CONCLUSIONS

Future research should concentrate on varied formulations and exposure regimens of ENDS to determine timing windows of exposures and ENDS formulations that may be harmful to craniofacial development.

Sex-Dependent Responses to Maternal Exposure to PM2.5 in the Offspring

Objective: Particulate matter (PM) with a diameter of 2.5 μm or less (PM_2.5) can cross the blood-placental barrier causing adverse foetal outcomes. However, the impact of maternal exposure to low-levels of PM_2.5 on liver health and the metabolic profile is unclear. This study aimed to investigate hepatic responses to long-term gestational low-dose PM_2.5 exposure, and whether the removal of PM after conception can prevent such effects. Method: Female Balb/c mice (8 weeks) were exposed to PM_2.5 (5 μg/day) for 6 weeks prior to mating, during gestation and lactation to model living in a polluted environment (PM group). In a sub-group, PM_2.5 exposure was stopped post-conception to model mothers moving to areas with clean air (pre-gestation, Pre) group. Livers were studied in 13-week old offspring. Results: Female offspring in both PM and Pre groups had increased liver triglyceride and glycogen levels, glucose intolerance, but reduced serum insulin and insulin resistance. Male offspring from only the Pre group had increased liver and serum triglycerides, increased liver glycogen, glucose intolerance and higher fasting glucose level. Markers of oxidative stress and inflammation were increased in females from PM and Pre groups. There was also a significant sex difference in the hepatic response to PM_2.5 with differential changes in several metabolic markers identified by proteomic analysis. Conclusions: Maternal PM exposure exerted sex-dependent effects on liver health with more severe impacts on females. The removal of PM_2.5 during gestation provided limited protection in the offspring’s metabolism regardless of sex.

Effects of air pollution on human health - Mechanistic evidence suggested by in vitro and in vivo modelling

Airborne particulate matter (PM) comprises both solid and liquid particles, including carbon, sulphates, nitrate, and toxic heavy metals, which can induce oxidative stress and inflammation after inhalation. These changes occur both in the lung and systemically, due to the ability of the small-sized PM (i.e. diameters ≤2.5 μm, PM_2.5) to enter and circulate in the bloodstream. As such, in 2016, airborne PM caused ∼4.2 million premature deaths worldwide. Acute exposure to high levels of airborne PM (eg. during wildfires) can exacerbate pre-existing illnesses leading to hospitalisation, such as in those with asthma and coronary heart disease. Prolonged exposure to PM can increase the risk of non-communicable chronic diseases affecting the brain, lung, heart, liver, and kidney, although the latter is less well studied. Given the breadth of potential disease, it is critical to understand the mechanisms underlying airborne PM exposure-induced disorders. Establishing aetiology in humans is difficult, therefore, in-vitro and in-vivo studies can provide mechanistic insights. We describe acute health effects (e.g. exacerbations of asthma) and long term health effects such as the induction of chronic inflammatory lung disease, and effects outside the lung (e.g. liver and renal change). We will focus on oxidative stress and inflammation as this is the common mechanism of PM-induced disease, which may be used to develop effective treatments to mitigate the adverse health effect of PM exposure.

Alterations of Mitochondrial Network by Cigarette Smoking and E-Cigarette Vaping

Toxins present in cigarette and e-cigarette smoke constitute a significant cause of illnesses and are known to have fatal health impacts. Specific mechanisms by which toxins present in smoke impair cell repair are still being researched and are of prime interest for developing more effective treatments. Current literature suggests toxins present in cigarette smoke and aerosolized e-vapor trigger abnormal intercellular responses, damage mitochondrial function, and consequently disrupt the homeostasis of the organelle's biochemical processes by increasing reactive oxidative species. Increased oxidative stress sets off a cascade of molecular events, disrupting optimal mitochondrial morphology and homeostasis. Furthermore, smoking-induced oxidative stress may also amalgamate with other health factors to contribute to various pathophysiological processes. An increasing number of studies show that toxins may affect mitochondria even through exposure to secondhand or thirdhand smoke. This review assesses the impact of toxins present in tobacco smoke and e-vapor on mitochondrial health, networking, and critical structural processes, including mitochondria fission, fusion, hyper-fusion, fragmentation, and mitophagy. The efforts are focused on discussing current evidence linking toxins present in first, second, and thirdhand smoke to mitochondrial dysfunction.

Personalized Treatment of Asthma: The Importance of Sex and Gender Differences

An individual's sex (nominally male or female, based on biological attributes) and gender (a complex term referring to socially constructed roles, behaviors, and expressions of identity) influence the clinical course of asthma in several ways. The physiologic development of the lungs and effects of sex hormones may explain why more boys than girls have asthma, and after puberty, more women than men have asthma. Female sex hormones have an impact throughout the life span and are associated with poor asthma control. Gender may influence exposure to asthma triggers, and sex and gender can influence the prevalence of comorbidities and interactions with health care professionals. Despite widely reported sex- and gender-based differences in asthma and asthma management, these issues frequently are not considered by health care professionals. There is also inconsistency regarding the use of "sex" and "gender" in scientific discourse; research is needed to define sex- and gender-based differences better and how they might interact to influence asthma outcomes. This review outlines the impact an individual's sex and gender can have on the pathogenesis, clinical course, diagnosis, treatment, and management of asthma.

Understanding Rising Electronic Cigarette Use

Vaping is the act of inhaling an aerosol generated by an electronic cigarette (e-cigarette), a battery-powered device that heats a reservoir of liquid, typically nicotine-containing, to deliver contents to the user. E-cigarettes were initially introduced as a means of smoking cessation, although evidence of their effectiveness is limited. There is a widespread perception that these products are a safer alternative to conventional cigarettes, driven in large part by marketing efforts by e-cigarette manufacturers. Yet to achieve vaporization, temperatures are so high that components of the device hardware, such as metals, plastics, rubber and foam, are aerosolized and inhaled along with the vaporized e-liquid containing nicotine, flavoring and solvents. We do not fully understand the health consequences of such aerosol exposure, particularly long-term effects, but short-term negative cardiovascular and respiratory effects have been demonstrated. Very few studies have evaluated the reproductive effect of e-cigarette use. We do not know whether vaping during pregnancy affects birth outcomes or the lifelong health of the fetus. There has been an exponential rise in the use of e-cigarettes in the United States since their introduction, particularly among youths, while concurrently there has been a laudable reduction in conventional cigarette use. It is imperative that obstetrician-gynecologists have a basic understanding of e-cigarettes, screen all patients as is consistently done for conventional smoking, and provide resources to patients about potential negative consequences of use.

Review of data on chemical content in an aerosol resulting from heating a tobacco or a solution used in e-cigarettes and in the smoke generated from the reference cigarettes

BACKGROUND

The article presents a review of the literature on the chemical composition of smoke generated from a standard cigarette and the aerosol generated after heating tobacco and chemical compounds formed in the aerosol of electronic cigarettes.

METHODS

The literature review was carried out on the PubMed online bibliographic database, Google search engine, Google Scholar based on science articles published in recent 20 years.

RESULTS

The bibliographic analysis shows that: replacing smoking in the traditional way by heating tobacco modifies significantly the content of chemical substances found in aerosol, the substances found in aerosols generated by e-cigarettes have proven toxic effects, e.g. pro-inflammatory effect on lung epithelial cells (e.g. crotonaldehyde) or a mutagenic effect (e.g. NNK), using e-cigarette aerosol does not rule out a health risk for people, which is not fully recognized at present.

CONCLUSIONS

Replacing smoking in the traditional way by heating tobacco modifies significantly the content of chemical substances found in aerosol. Using e-cigarette aerosol does not rule out a health risk for people, because the substances found in aerosols generated by e-cigarettes have proven toxic effects.

Associations between electronic nicotine delivery systems and birth outcomes

OBJECTIVES

Nicotine crosses the placenta and is a known teratogen. The use of electronic nicotine delivery systems (ENDS) has increased among pregnant women in the US, but there is limited knowledge about their effects on birth outcomes. We examined the associations between ENDS and cigarette use during pregnancy with birth outcomes.

METHODS

We conducted a cross-sectional analysis of 57,046 respondents from 32 US states in the 2016-2017 Pregnancy Risk Assessment Monitoring System. Respondents self-reported use of ENDS and cigarettes during the last 3 months of pregnancy; this was linked with birth outcomes documented on the birth certificate, including birth weight, gestational age, small-for-gestational age, and preterm birth.

RESULTS

During the last 3 months of pregnancy, 0.5% of women used ENDS only, 0.8% were dual users of ENDS and cigarettes, and 8.0% used cigarettes only. In adjusted models, infants of women who used ENDS only weighed 57.8 grams less (95% CI -134.2, 18.6; p = .14) and were born 0.21 weeks earlier (95% CI -0.45, 0.03; p = .09) than infants of non-users. Infants born to dual users were 193.9 grams less (95% CI -274.9, -112.8; p < .01) and had a 1.93 higher odds of being born small-for-gestational age (95% CI 1.31, 2.83; p < .01) than infants of non-users.

CONCLUSIONS

Our results provide some indication that prenatal ENDS use may adversely affect birth outcomes by reducing birth weight and gestational age. Estimates were imprecise, suggesting that larger samples of ENDS users with more detailed information about patterns of use are needed.

Particulate Matter, an Intrauterine Toxin Affecting Foetal Development and Beyond

Air pollution is the 9th cause of the overall disease burden globally. The solid component in the polluted air, particulate matters (PMs) with a diameter of 2.5 μm or smaller (PM_2.5) possess a significant health risk to several organ systems. PM_2.5 has also been shown to cross the blood–placental barrier and circulate in foetal blood. Therefore, it is considered an intrauterine environmental toxin. Exposure to PM_2.5 during the perinatal period, when the foetus is particularly susceptible to developmental defects, has been shown to reduce birth weight and cause preterm birth, with an increase in adult disease susceptibility in the offspring. However, few studies have thoroughly studied the health outcome of foetuses due to intrauterine exposure and the underlying mechanisms. This perspective summarises currently available evidence, which suggests that intrauterine exposure to PM_2.5 promotes oxidative stress and inflammation in a similar manner as occurs in response to direct PM exposure. Oxidative stress and inflammation are likely to be the common mechanisms underlying the dysfunction of multiple systems, offering potential targets for preventative strategies in pregnant mothers for an optimal foetal outcome.

Sex dependent effect of maternal e-nicotine on F1 Drosophila development and airways

E-cigarettes are heavily advertised as healthier alternative to common tobacco cigarettes, leading more and more women to switch from regular cigarettes to ENDS (electronic nicotine delivery system) during pregnancy. While the noxious consequences of tobacco smoking during pregnancy on the offspring health are well-described, information on the long-term consequences due to maternal use of e-cigarettes do not exist so far. Therefore, we aimed to investigate how maternal e-nicotine influences offspring development from earliest life until adulthood. To this end, virgin female Drosophila melanogaster flies were exposed to nicotine vapor (8 µg nicotine) once per hour for a total of eight times. Following the last exposure, e-nicotine or sham exposed females were mated with non-exposed males. The F1-generation was then analyzed for viability, growth and airway structure. We demonstrate that maternal exposure to e-nicotine not only leads to reduced maternal fertility, but also negatively affects size and weight, as well as tracheal development of the F1-generation, lasting from embryonic stage until adulthood. These results not only underline the need for studies investigating the effects of maternal vaping on offspring health, but also propose our established model for analyzing molecular mechanisms and signaling pathways mediating these intergenerational changes.

Study on E-Cigarettes and Pregnancy (STEP) - Results of a Mixed Methods Study on Risk Perception of E-Cigarette Use During Pregnancy

Introduction E-cigarette use during pregnancy is a risk factor for maternal and fetal health. Early studies on animals showed that in utero exposure to e-cigarettes can have negative health outcomes for the fetus. There has been only limited research into the risk perceptions of e-cigarette use during pregnancy. This study was conducted to comprehensively characterize the constructs of risk perceptions with regard to e-cigarette use during pregnancy using an I ntegrated H ealth B elief M odel (IHBM).

Methods Our ST udy on E -cigarettes and P regnancy (STEP) used a mixed methods approach, with the study divided into an initial qualitative part and a quantitative part. A netnographic approach was used for the first part, which consisted of the analysis of 1552 posts from 25 German-language online discussion threads on e-cigarette use during pregnancy. Using these qualitative results, a quantitative questionnaire was developed to explore risk perception constructs about e-cigarette use during pregnancy. This questionnaire was subsequently administered to pregnant women (n = 575) in one hospital in Hamburg, Germany. Descriptive and bivariate analysis was used to examine differences in risk perception according to participantsʼ tobacco and e-cigarette user status before and during pregnancy. While the study design, methods and sample have been extensively described in our recently published study protocol in the January 2020 issue of Geburtshilfe und Frauenheilkunde , this paper is devoted to a presentation of the results of our mixed methods study.

Results Themes related to perceived threats identified in the qualitative study part were nicotine-related health risks and potential health risks of additional ingredients . Perceived benefits were possibility and facilitation of smoking cessation and a presumed potential to reduce harm . The subsequent quantitative part showed that nearly all participants (99.3%) perceived e-cigarettes which contained nicotine as constituting a threat to the health of the unborn child. The most commonly perceived barrier was health-related (96.6%), while the most commonly perceived benefit was a reduction in the amount of tobacco cigarettes consumed (31.8%). We found that particularly perceived benefits varied depending on the participantʼs tobacco and e-cigarette user status.

Conclusion When considering future prevention strategies, the potential health risks and disputed effectiveness of e-cigarettes as a tool for smoking cessation need to be taken into account and critically discussed.

Brain health is independently impaired by E-vaping and high-fat diet

Tobacco smoking and high-fat diet (HFD) independently impair short-term memory. E-cigarettes produce e-vapour containing flavourings and nicotine. Here, we investigated whether e-vapour inhalation interacts with HFD to affect short-term memory and neural integrity. Balb/c mice (7 weeks, male) were fed a HFD (43% fat, 20 kJ/g) for 16 weeks. In the last 6 weeks, half of the mice were exposed to tobacco-flavoured e-vapour from nicotine-containing (18 mg/L) or nicotine-free (0 mg/L) e-fluids twice daily. Short-term memory function was measured in week 15. HFD alone did not impair memory function, but increased brain phosphorylated (p)-Tau and astrogliosis marker, while neuron and microglia levels were decreased. E-vapour exposure significantly impaired short-term memory function independent of diet and nicotine. Nicotine free e-vapour induced greater changes compared to the nicotine e-vapour and included, increased systemic cytokines, increased brain p-Tau and decreased postsynaptic density protein (PSD)-95 levels in chow-fed mice, and decreased astrogliosis marker, increased microglia and increased glycogen synthase kinase levels in HFD-fed mice. Increased hippocampal apoptosis was also differentially observed in chow and HFD mice. In conclusion, E-vapour exposure impaired short-term memory independent of diet and nicotine, and was correlated to increased systemic inflammation, reduced PSD-95 level and increased astrogliosis in chow-fed mice, but decreased gliosis and increased microglia in HFD-fed mice, indicating the inflammatory nature of e-vapour leading to short term memory impairment.

Electronic Cigarettes and Fecundability: Results From a Prospective Preconception Cohort Study

Although electronic cigarette (e-cigarette) aerosol contains similar toxicants to combustible cigarettes, few studies have examined their influence on fecundability. We assessed the association between e-cigarette use and fecundability, overall and according to combustible cigarette smoking history, in a cohort of 4,586 North American women (aged 21-45 years) enrolled during 2017-2020 in Pregnancy Study Online, a Web-based prospective preconception study. Women reported current and former e-cigarette use on baseline and follow-up questionnaires, and they completed bimonthly follow-up questionnaires until self-reported pregnancy or censoring. Fecundability ratios and 95% confidence intervals were calculated using proportional probabilities models, controlling for potential confounders. Overall, 17% of women had ever used e-cigarettes and 4% were current users. Compared with never use of e-cigarettes, current e-cigarette use was associated with slightly lower fecundability (fecundability ratio = 0.84, 95% confidence interval (CI): 0.67, 1.06). Compared with current nonusers of e-cigarettes and combustible cigarettes, fecundability ratios were 0.83 (95% CI: 0.54, 1.29) for current dual users of e-cigarettes and combustible cigarettes, 0.91 (95% CI: 0.70, 1.18) for current e-cigarette users who were nonsmokers of combustible cigarettes, and 1.01 (95% CI: 0.85, 1.20) for nonusers of e-cigarettes who were current smokers of combustible cigarettes. Current e-cigarette use was associated with slightly reduced fecundability, but estimates of its independent and joint associations with combustible cigarette smoking were inconsistent and imprecise.

A Qualitative Study of Factors Influencing Adherence among Pregnant Women Taking Part in a Trial of E-Cigarettes for Smoking Cessation

Use of e-cigarettes (vaping) has potential to help pregnant women stop smoking. This study explored factors influencing adherence among participants in the vaping arm of the first trial of vaping for smoking cessation in pregnancy. We conducted semi-structured telephone interviews (n = 28) with women at three-months postpartum. Interviews were analysed using thematic analysis, informed by the Theoretical-Domains Framework, Necessity-Concerns Framework and Perceptions and Practicalities Approach. Interviewees generally reported high levels of vaping. We found that: (1) intervention adherence was driven by four necessity beliefs-stopping smoking for the baby, and vaping for harm reduction, smoking cessation or as a last resort; (2) necessity beliefs outweighed vaping concerns, such as dependence and safety; (3) adherence was linked to four practicalities themes, acting as barriers and facilitators to vaping-device and e-liquid perceptions, resources and support, whether vaping became habitual, and social and environmental factors; and (4) intentional non-adherence was rare; unintentional non-adherence was due to device failures, forgetting to vape, and personal circumstances and stress. Pregnant smokers provided with e-cigarettes, and with generally high levels of vaping, had positive beliefs about the necessity of vaping for smoking cessation which outweighed concerns about vaping. Non-adherence was mainly due to unintentional factors.

Effects of E-Cigarette Exposure on Prenatal Life and Childhood Respiratory Health: A Review of Current Evidence

In the last decade, widespread use of E-cigarettes (EC) has occurred all over the world. Whereas, a large amount of evidence on harm to children from conventional cigarette exposure is available, data on health effects in this population throughout different vulnerability windows are still a matter of concern. Exposure to EC during pregnancy may compromise placental function, resulting in fetal structural abnormalities. Specifically, this may cause physio-pathologic changes in the developing lung, which in turn may impair respiratory health later in life. Furthermore, there is evidence that using EC can cause both short- and long-term respiratory problems in the pediatric population and there is great concern for future young people with nicotine addiction. The low parental perception of the risks connected to EC exposure for children increases their susceptibility to harmful effects from passive vaping. This minireview aims to summarize the current evidence focusing on: (i) prenatal effects of EC passive exposure; (ii) post-natal respiratory effects of EC exposure in youth; (iii) parental attitudes toward EC use and perception of children's health risks connected to EC exposure; and (iv) addressing gaps in our current evidence.

Transcriptomic analysis of tobacco-flavored E-cigarette and menthol-flavored E-cigarette exposure in the human middle ear

Electronic cigarettes (e-cigarettes) are the most widely used electronic nicotine delivery systems and are designed to imitate smoking and aid in smoking cessation. Although the number of e-cigarette users is increasing rapidly, especially among young adults and adolescents, the potential health impacts and biologic effects of e-cigarettes still need to be elucidated. Our previous study demonstrated the cytotoxic effects of electronic liquids (e-liquids) in a human middle ear epithelial cell (HMEEC-1) line, which were affected by the manufacturer and flavoring agents regardless of the presence of nicotine. In this study, we aimed to evaluate the gene expression profile and identify potential molecular modulator genes and pathways in HMEEC-1 exposed to two different e-liquids (tobacco- and menthol-flavored). HMEEC-1 was exposed to e-liquids, and RNA sequencing, functional analysis, and pathway analysis were conducted to identify the resultant transcriptomic changes. A total of 843 genes were differentially expressed following exposure to the tobacco-flavored e-liquid, among which 262 genes were upregulated and 581 were downregulated. Upon exposure to the menthol-flavored e-liquid, a total of 589 genes were differentially expressed, among which 228 genes were upregulated and 361 were downregulated. Among the signaling pathways associated with the differentially expressed genes mediated by tobacco-flavored e-liquid exposure, several key molecular genes were identified, including IL6 (interleukin 6), PTGS2 (prostaglandin-endoperoxide synthase 2), CXCL8 (C-X-C motif chemokine ligand 8), JUN (Jun proto-oncogene), FOS (Fos proto-oncogene), and TP53 (tumor protein 53). Under menthol-flavored e-liquid treatment, MMP9 (matrix metallopeptidase 9), PTGS2 (prostaglandin-endoperoxide synthase 2), MYC (MYC proto-oncogene, bHLH transcription factor), HMOX1 (heme oxygenase 1), NOS3 (nitric oxide synthase 3), and CAV1 (caveolin 1) were predicted as key genes. In addition, we identified related cellular processes, including inflammatory responses, oxidative stress and carcinogenesis, under exposure to tobacco- and menthol-flavored e-liquids. We identified differentially expressed genes and related cellular processes and gene signaling pathways after e-cigarette exposure in human middle ear cells. These findings may provide useful evidence for understanding the effect of e-cigarette exposure.

Vaping During Pregnancy: What Are the Potential Health Outcomes and Perceptions Pregnant Women Have?

The prevalence of electronic nicotine delivery systems, such as vaping, is a growing public health concern, and there is limited information on the use of these devices during pregnancy. The objective of this rapid review was to summarize the available literature on human studies of the potential maternal or fetal health effects of vaping or women's perceptions of vaping during pregnancy. A systematic search was completed in the following databases: Medline, EMBASE, Scopus, Web of Science, and CINAHL. A search strategy was developed combining the terms pregnancy and vaping. Findings were divided into two groups and summarized as: 1) Health outcomes following vaping during pregnancy; and 2) Perceptions pregnant women have related to vaping during pregnancy. A total of 760 articles were retrieved and, after applying the inclusion/exclusion criteria and screening, 19 studies were included. Five included studies provided evidence on potential health outcomes and 14 were focused on perceptions. There is emerging evidence that vaping during pregnancy may increase the risk of small for gestational age newborns. Pregnant women generally report that they used vaping products during pregnancy for smoking cessation and perceived that this was a healthier alternative to traditional cigarettes. Overall, there was consensus that there is a lack of information on maternal and fetal health outcomes following vaping during pregnancy. Based on the findings of this rapid review, there is an urgent need for high-quality studies in pregnant women to evaluate the potential in utero and long-term effects of exposure to prenatal vaping.

Replacing smoking with vaping during pregnancy: Impacts on metabolic health in mice

Smoking is a significant risk factor for the development of metabolic diseases. Due to social pressures to quit smoking, many pregnant women are vaping as an alternative nicotine source. However, the metabolic consequences of replacing tobacco cigarettes with e-cigarettes during pregnancy are unknown. Therefore, in the mothers and their offspring, we investigated the metabolic and hepatic impacts of replacing cigarette smoke with e-vapour during pregnancy. Female BALB/c mice were either air-exposed or cigarette smoke-exposed (SE) from six weeks before pregnancy until lactation. At mating, a subset of the SE mice were instead exposed to e-vapour. Markers of glucose and lipid metabolism were measured in the livers and plasma, from the mothers and their male offspring (13 weeks). In the SE mothers, plasma insulin levels were reduced, leading to downstream increases in hepatic gluconeogenesis and plasma non-esterified fatty acids (NEFA). In the e-vapour replacement mothers, these changes were not as significant. In the SE offspring, there was impaired glucose tolerance, and increased plasma NEFA and liver triglyceride concentrations. E-vapour replacement restored lipid homeostasis but did not improve glucose tolerance. Therefore, in a murine model, low dose e-cigarette replacement during pregnancy is less toxic than cigarette smoke.

E-Cigarette Use Patterns and High-Risk Behaviors in Pregnancy: Behavioral Risk Factor Surveillance System, 2016-2018

INTRODUCTION

The prevalence of e-cigarette use has increased dramatically in the last decade in the U.S. Understanding the prevalence, patterns of use, and risk factor associations of e-cigarette use in pregnant women is particularly important, as this could have potential health implications for the mother and the developing child.

METHODS

Using Behavioral Risk Factor Surveillance System Survey data from 2016 to 2018, adult women of reproductive age (18-49 years) who reported being pregnant (n=7,434) were studied. Self-reported current e-cigarette use was the main exposure. Other measures included combustible cigarette smoking status and high-risk behaviors (including other tobacco, marijuana, or heavy alcohol use; binge drinking; and others). All analyses were done in 2019.

RESULTS

Approximately 2.2% of pregnant women reported current e-cigarette use, of whom 0.6% reported daily use. The highest prevalence of e-cigarette use was observed in the youngest age group of pregnant women (3.2%), with 41.7% of all pregnant current e-cigarette users being aged 18-24 years. There was a marked increase in the prevalence of current use of e-cigarettes among pregnant women from 1.9% in 2016 to 3.8% in 2018. Approximately 46% of pregnant current e-cigarette users reported concomitant cigarette smoking. Compared with pregnant never e-cigarette users, pregnant current e-cigarette users had a higher prevalence of other tobacco product use, marijuana use, heavy alcohol intake, binge drinking, and other high-risk behaviors.

CONCLUSIONS

These findings underscore the need to strengthen prevention and policy efforts, specifically in the vulnerable subgroup of pregnant women.

[Other Methods of Consumption: Electronic Cigarette, Heated Tobacco, Shisha and Snus - CNGOF-SFT Expert Report and Guidelines on the management for Smoking Management During Pregnancy]

Other methods of cigarette consumption include a variety of electronic products, as well as heated tobacco, snus and shisha. The questions in this chapter are: what other methods of consumption are used during pregnancy (either electronic or containing tobacco) and what is their prevalence? What is their benefit/risk balance? Can their use during pregnancy be proposed? Although the fetus is not exposed to the combustible toxins of tobacco, e-cigarette products may contain nicotine, which maintains the exposure of the fetus. Further research is needed on the other components of the electronic cigarette, such as flavorings and propylene glycol and/or glycerol, in order to assess the benefit/risk balance. In addition, some solvents contain ethanol. In the current state of knowledge, the precautionary principle should be respected and not recommend the initiation or continuation of the electronic cigarette during pregnancy (professional agreement). For smoking cessation or electronic cigarette cessation, it is recommended to provide the same advice and to use methods that have already been evaluated (professional agreement). For the JUUL, there are currently no data on obstetrical outcome when used. The use of shisha during pregnancy is associated with decreased fetal growth. It is recommended not to use shisha during pregnancy (GradeC). There are currently no data on the use of heated tobacco and obstetrical outcome.

E-cigarettes damage the liver and alter nutrient metabolism in pregnant mice and their offspring

Approximately 15% of pregnant women vape electronic cigarettes (e-cigarettes), exposing the fetus to a range of toxic compounds, including nicotine and by-products of e-cigarette liquid (e-liquid) pyrolysis. Owing to the recent emergence of these products, research mainly focuses on immediate users, and not on in utero exposure. Therefore, this study aimed to understand the impact of intrauterine e-cigarette vapor (e-vapor) exposure, with and without nicotine, on liver metabolic markers in the male offspring. E-vapor was generated using an e-cigarette filled with tobacco-flavored e-liquid (18 or 0 mg/mL nicotine). Female Balb/c mice were exposed to e-vapor for 6 weeks before mating, through gestation and lactation, without direct exposure to the offspring. Livers and plasma from dams and male offspring (13 weeks old) were examined. Exposure to nicotine-free e-vapor promoted metabolic changes and liver damage in both the dams and their offspring. Furthermore, exposure to nicotine-containing e-vapor did not cause liver damage but induced hepatic steatosis in the adult offspring. Therefore, maternal vaping is detrimental to both the dams and their offspring, with nicotine providing a potential protective effect.

Neurotoxicity of e-cigarettes

It appears that electronic cigarettes (EC) are a less harmful alternative to conventional cigarette (CC) smoking, as they generate substantially lower levels of harmful carcinogens and other toxic compounds. Thus, switching from CC to EC may be beneficial for smokers. However, recent accounts of EC- or vaping-associated lung injury (EVALI) has raised concerns regarding their adverse health effects. Additionally, the increasing popularity of EC among vulnerable populations, such as adolescents and pregnant women, calls for further EC safety evaluation. In this state-of-the-art review, we provide an update on recent findings regarding the neurological effects induced by EC exposure. Moreover, we discuss possible neurotoxic effects of nicotine and numerous other chemicals which are inherent both to e-liquids and EC aerosols. We conclude that in recognizing pertinent issues associated with EC usage, both government and scientific researchers must address this public health issue with utmost urgency.

In utero exposures to electronic-cigarette aerosols impair the Wnt signaling during mouse lung development

Currently, more than 9 million American adults, including women of childbearing age, use electronic-cigarettes (e-cigs). Further, the prevalence of maternal vaping now approaching 10% is similar to that of maternal smoking. Little, however, is known about the effects of fetal exposures to nicotine-rich e-cig aerosols on lung development. In this study, we assessed whether in utero exposures to e-cig aerosols compromised lung development in mice. A third-generation e-cig device was used to expose pregnant BALB/c mice by inhalation to 36 mg/mL of nicotine cinnamon-flavored e-cig aerosols for 14-31 days. This included exposures for either 12 days before mating plus during gestation (preconception groups) or only during gestation (prenatal groups). Respective control mice were exposed to filtered air. Subgroups of offspring were euthanized at birth or at 4 wk of age. Compared with respective air-exposed controls, both preconception and prenatal exposures to e-cig aerosols significantly decreased the offspring birth weight and body length. In the preconception group, 7 inflammation-related genes were downregulated, including 4 genes common to both dams and fetuses, denoting an e-cig immunosuppressive effect. Lung morphometry assessments of preconception e-cig-exposed offspring showed a significantly increased tissue fraction at birth. This result was supported by the downregulation of 75 lung genes involved in the Wnt signaling, which is essential to lung organogenesis. Thus, our data indicate that maternal vaping impairs pregnancy outcomes, alters fetal lung structure, and dysregulates the Wnt signaling. This study provides experimental evidence for future regulations of e-cig products for pregnant women and developmentally vulnerable populations.

Use of ENDS and Cigarettes During Pregnancy

INTRODUCTION

Although the use of alternative tobacco products has been increasing among women and adolescents, research on the use of ENDS during pregnancy has been limited. This study examines the prevalence and sociodemographic characteristics of ENDS and cigarette use during pregnancy.

METHODS

This cross-sectional analysis of the 2016 Pregnancy Risk Assessment Monitoring System used data on self-reported use of ENDS and cigarettes during the last 3 months of pregnancy among 33,964 women from 29 states and New York City. Data were analyzed in 2019.

RESULTS

The overall prevalence of prenatal ENDS use was 1.2% and cigarette use was 7.7%, varying from 0.6% and 1.8% in New York City to 4.4% and 22.7% in West Virginia. In adjusted models, white women were more likely to use ENDS (AOR=4.68, 95% CI=2.91, 7.54) than black women. Women with increasing years of education were also less likely to use ENDS. Women who used cigarettes during pregnancy were 11.05 times (95% CI=7.40, 16.48) more likely to also use ENDS prenatally. Associations between sociodemographic characteristics and cigarette use during pregnancy were consistent with the findings for ENDS.

CONCLUSIONS

Pregnant women across the U.S. are using ENDS and cigarettes. Surveillance is essential to continue monitoring trends in prenatal use of tobacco products and understand the implications on pregnancy and infant outcomes.

STudy on E-Cigarettes and Pregnancy (STEP) - Study Protocol of a Mixed Methods Study on Risk Perception of E-Cigarette Use During Pregnancy and Sample Description

Introduction During pregnancy, the mother's healthy lifestyle is crucial for the health of the fetus. Potential risk factors for maternal and child health should therefore be identified and reduced as early as possible. The consumption of e-cigarettes represents one of these potential risk factors. Exploring risk perceptions about e-cigarette use during pregnancy can provide early indications of possible user motives. Therefore, our mixed methods ST udy on E -cigarettes and P regnancy (STEP) aimed to comprehensively analyze risk perceptions about e-cigarette use during pregnancy based on an I ntegrated H ealth B elief M odel (IHBM). This paper describes the study design, methods, sample population and limitations of STEP. Methods Our sequential mixed methods study combined qualitative and quantitative approaches. In the qualitative section of the study which preceded the quantitative part of the study, we aimed to characterize risk perceptions about e-cigarette use during pregnancy. We used a netnographic research approach which analyzed discussion threads in online forums dealing with e-cigarette use during pregnancy. The analysis was based on an IHBM. Identified themes were incorporated in the questionnaire which was developed for the quantitative part of the study. The quantitative section aimed to quantify, among other things, perceived threats, barriers and benefits and to explore differences in risk perception according to sociodemographic characteristics and tobacco and e-cigarette usage. Results In the qualitative section, 1552 posts in 25 online discussion threads dealing, inter alia, with e-cigarette use during pregnancy were identified. The quantitative part looked at the responses in the questionnaires handed in by 575 pregnant women who attended a hospital in Hamburg (Germany) from April 2018 to January 2019 (response rate: 27.5%). Conclusion Data collection was successful for both the qualitative and quantitative parts of the study. When interpreting the results of STEP, different limitations should be taken into account. The results of STEP provide starting points for the development of tailored preventive measures for pregnant women.

The Changing Process of Women's Smoking Status Triggered by Pregnancy

Although pregnancy is the trigger for many women to stop smoking, often they are unable to maintain cessation, undoing any health benefits for themselves and their children. Smoking is a complex phenomenon both before and after pregnancy, influenced by social background, relationships, and the specific experience of pregnancy and delivery. Therefore, it is necessary to clarify the experience and process of changes in women's smoking status from pregnancy to after delivery. To explore possibilities for better smoking cessation support, the objective of this study was to clarify the changing process of smoking status from pregnancy to after delivery in women for whom pregnancy triggered a smoking cessation. We analyzed data obtained through semi-structured interviews with 31 women, using the grounded theory approach. Women reconsidered their smoking status, either quitting or smoking fewer cigarettes, because of externally motivated changes due to concerns regarding the influence of smoking on pregnancy and children. To prevent smoking relapse, it is important for the women themselves, as well as those around them, to appreciate their cessation, facilitating internal motivation and assessment of the situation. Furthermore, it is important to provide support, by implementing the process revealed in this study, not only during pregnancy but for an entire lifetime.

What lessons have we learnt about the impact of maternal cigarette smoking from animal models?

Maternal first- or second-hand tobacco smoking during pregnancy is still common albeit that the detrimental effects to the unborn child are well known. Maternal tobacco cigarette smoking can affect multiple organ systems in the offspring, rendering them at increased risk of various conditions throughout life (eg. intrauterine underdevelopment, asthma, substance abuse, diabetes). However, this review will only focus on its impact on the brain and the related molecular changes in the offspring based on evidence from animal studies. Although epidemiological studies have identified the associations between maternal cigarette smoke exposure (SE) and brain disorders, animal models can help identify the underlying mechanisms and test interventions. Human studies have found that maternal SE is closely linked to small brain size and changes in brain structure and associated with a high risk of cognitive defects. Animal models suggest that this may be due to increased brain oxidative stress and inflammation during the neonatal period, leading to increased brain cell apoptosis in adulthood. There is a distinct gender bias of such impacts, where male offspring are more affected than females. Female offspring seem to have developed the adaptation by increasing endogenous antioxidant levels. Indeed, animal studies have shown that using antioxidant supplementation during pregnancy can improve neurological outcomes in male offspring, however, the efficacy in humans is yet to be confirmed. Furthermore, some animal studies suggested nicotine as the key player in intrauterine underdevelopment due to maternal SE, while human clinical trials using nicotine replacement therapy do not support this mechanism. This review will discuss the possible reasons.

The impact of perinatal nicotine exposure on fetal lung development and subsequent respiratory morbidity

Maternal smoking during pregnancy remains as a significant public health crisis as it did decades ago. Although its prevalence is decreasing in high-income countries, it has worsened globally, along with a concerning emergence of electronic-cigarette usage within the last two decades. Extensive epidemiologic and experimental evidence exists from both human and animal studies, demonstrating the detrimental long-term pulmonary outcomes in the offspring of mothers who smoke during pregnancy. Even secondhand and thirdhand smoke exposure to the developing lung might be as or even more harmful than firsthand smoke exposure. Furthermore, these effects are not limited only to the exposed progeny, but can also be transmitted transgenerationally. There is compelling evidence to support that the majority of the effects of perinatal smoke exposure on the developing lung, including the transgenerational transmission of asthma, is mediated by nicotine. Nicotine exposure induces cell-specific molecular changes in lungs, which offers a unique opportunity to prevent, halt, and/or reverse the resultant damage through targeted molecular interventions. Experimentally, the proposed interventions, such as administration of peroxisome proliferator-activated receptor gamma (PPARγ) agonists can not only block but also potentially reverse the perinatal nicotine exposure-induced respiratory morbidity in the exposed offspring. However, the development of a safe and effective intervention is still many years away. In the meantime, electropuncture at specific acupoints appears to be emerging as a more practical and safe physiologic approach to block the harmful pulmonary consequences of perinatal nicotine exposure.

Perceived threats, benefits and barriers of e-cigarette use during pregnancy. A qualitative analysis of risk perception within existing threads in online discussion forums

OBJECTIVE

Previous studies have shown that e-cigarettes are perceived as being less harmful than tobacco cigarettes by pregnant women and might be used to quit smoking during pregnancy. Our aim was to further explore and characterise perceived threats, benefits and barriers of e-cigarette use during pregnancy.

METHODS

Our STudy on E-cigarettes and Pregnancy (STEP) was, among others, based on a netnographic approach of analysing existing threads in German-speaking online discussion forums dealing with perceived threats and benefits of e-cigarette use during pregnancy. For the analysis, we used an inductive-deductive qualitative content analysis.

FINDINGS

Based on 25 online discussion threads containing 1552 posts, we identified perceived threats, perceived benefits and perceived barriers to e-cigarette use during pregnancy, among others, as main themes. Subthemes identified within the main theme perceived threats were severe nicotine related health risks, potential health risks of additional ingredients, relative risks and lack of knowledge and research studies. As perceived benefits, we identified possibility and facilitation of smoking cessation, harm reduction and financial benefits. Perceived barriers were lack of satisfaction and social stigma.

CONCLUSION

Our qualitative results suggest that the perception of the health threats related to e-cigarette use during pregnancy varies according to the nicotine content and the perception of relative risks compared with tobacco cigarettes. In addition to this, risk perception is defined through further health and non-health related barriers and benefits (e.g. suitability of e-cigarettes as a smoking cessation aid, social stigma).

Neurological Effects in the Offspring After Switching From Tobacco Cigarettes to E-Cigarettes During Pregnancy in a Mouse Model

Maternal smoking is currently a public health concern and has been associated with a number of complications in the offspring. E-cigarettes are gaining popularity as a “safer” alternative to tobacco cigarettes during pregnancy, however, there are a limited number of studies to suggest that it is actually “safe.” Balb/C female mice were exposed to ambient air (n = 8; Sham), or tobacco cigarette smoke (n = 8; SE) before gestation, during gestation and lactation. A third group was exposed to cigarette smoke before gestation followed by e-cigarette aerosols during gestation and lactation (n = 8; Switch). Male offspring (12-week old, n = 10–14/group) underwent behavioral assessments to investigate short-term memory, anxiety, and activity using the novel object recognition and elevated plus maze tests. Brains were collected at postnatal day (P)1, P20, and Week 13 for global DNA methylation, epigenetic gene expression, and neuronal cell counts. The offspring from mothers switching to e-cigarettes exhibited no change in exploration/activity but showed a decrease in global DNA methylation, Aurora Kinase (Aurk) A and AurkB gene expression and a reduction in neuronal cell numbers in the cornu ammonis 1 region of the dorsal hippocampus compared with the SE group. Continuous tobacco cigarette smoke exposure during pregnancy resulted in marked neurological deficits in the offspring. Switching to e-cigarettes during pregnancy reduced these neurological deficits compared with cigarette smoke exposure. However, neurological changes were still observed, so we therefore conclude that e-cigarette use during pregnancy is not advised.

The use of electronic nicotine delivery systems during pregnancy and the reproductive outcomes: A systematic review of the literature

INTRODUCTION

Use of electronic nicotine delivery systems (ENDS) among pregnant women is of great concern. To our knowledge the current literature provides conflicting views regarding the uncertainties of the effects of ENDS use during pregnancy on the health of the fetus.

METHODS

We searched PubMed, CINAHL, and EMBASE, for the period 2007 to October 2017 for terms to identify publications on ENDS use during pregnancy and the reproductive outcomes. We updated the search for the period November 2017 to November 2018 using Ovid Medline. We obtained full text of articles and present a summary of the contents.

RESULTS

We found no studies of pregnant women exposed to ENDS use and its effect on their fetus or neonates. However, there is a growing body of experimental studies in animals that suggest that nicotine in ENDS alters DNA methylation, induces birth defects, reduces the birth weight, and affects the development of the heart and lungs of their offspring. A large population-based cohort study in the United States estimated that 5% of pregnant women were current ENDS users in 2014; most of them also smoked cigarettes. Surveys conducted among practitioners indicate that there is a need to screen and counsel pregnant women. Systematic reviews and meta-analysis of studies of women who used smokeless tobacco during pregnancy suggest that prenatal nicotine alone is a risk factor for low birth weight, premature delivery, and stillbirth.

CONCLUSIONS

There were no previous studies assessing the reproductive effects of ENDS use during pregnancy. However, prenatal exposure to nicotine is known to be harmful to the fetus and the pregnancy.

Analytical Method for Measurement of Tobacco-Specific Nitrosamines in E-Cigarette Liquid and Aerosol

An experimental method was developed and validated for the collection and analysis of tobacco-specific nitrosamines (TSNAs) that are present in electronic cigarette (EC) liquid or are released from aerosol samples using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) system. As part of this study, the relative recovery of four target TSNAs was assessed by spiking standards in a mixture of propylene glycol and vegetable glycerin. Recovery was assessed against two major variables: (1) the chemical media (solution) selected for sample dilution (acetonitrile [ACN] vs. ammonium acetate [AA]) and (2) the type of sampling filter used (Cambridge filter pad [CFP] vs. quartz wool [QW] tube). The average recovery of TSNAs in terms of variable 1 was 134 ± 22.1% for ACN and 92.6 ± 8.27% for AA. The average recovery in terms of variable 2 was 83.4 ± 7.33% for QW and 58.5 ± 12.9% for CFP. Based on these conditions, the detection limits of N′-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N′-nitrosoanatabine (NAT), and N′-nitrosoanabasine (NAB) were calculated as 4.40, 4.47, 3.71, and 3.28 ng mL−1, respectively. The concentration of TSNAs in liquid and aerosol samples of six commercial EC solutions was measured as below the detection limit.