Effects of radiofrequency electromagnetic field (RF-EMF) exposure on male fertility: A systematic

Abstract

Effects of radiofrequency electromagnetic field (RF-EMF) exposure on male fertility: A systematic review of experimental studies on non-human mammals and human sperm in vitro (SR 4) My note: Numerous problems have been identified with this paper and other systematic reviews commissioned by the WHO for an upcoming monograph on radio frequency effects. Cordelli E, Ardoino L, Benassi B, Consales C, Eleuteri P, Marino C, Sciortino M, Villani P, Brinkworth MH, Chen G, McNamee JP, Wood AW, Belackova L, Verbeek J, Pacchierotti F. Effects of radiofrequency electromagnetic field (RF-EMF) exposure on male fertility: A systematic review of experimental studies on non-human mammals and human sperm in vitro. Environment International. 2024, doi: 10.1016/j.envint.2024.108509. Open access paper: sciencedirect.com Highlights Risk of bias, inconsistency, publication bias weakened the certainty of results RF-EMF is unlike to decrease the fecundity of exposed male rodents. RF-EMF may affect testicular tissue and sperm quality but the evidence is uncertain. Impact on surrogate markers of fertility may not translate into functional effects. Abstract Background The World Health Organization is coordinating an international project aimed at systematically reviewing the evidence regarding the association between radiofrequency electromagnetic field (RF-EMF) exposure and adverse health effects. Reproductive health outcomes have been identified among the priority topics to be addressed. Objectives To evaluate the effect of RF-EMF exposure on male fertility of experimental mammals and on human sperm exposed in vitro. Methods Three electronic databases (PubMed, Scopus and EMF Portal) were last searched on September 17, 2022. Two independent reviewers screened the studies, which were considered eligible if met the following criteria: 1) Peer-reviewed publications of sham controlled experimental studies, 2) Non-human male mammals exposed at any stage of development or human sperm exposed in vitro, 3) RF-EMF exposure within the frequency range of 100 kHz-300 GHz, including electromagnetic pulses (EMP), 4) one of the following indicators of reproductive system impairment:•decrease of fertility: rate of infertile males, rate of nonpregnant females, litter size and in vitro fertilization rate;•effects on semen quality: in animal studies sperm count, in both animal and in vitro studies sperm vitality, morphology and DNA/chromatin alterations;•reproductive organ toxicity: testis-epididymis weight, testis or epididymis histology, testis histomorphometry, testicular cell death, estimated testicular cell production;•hormonal effects: testosterone level.Two reviewers extracted study characteristics and outcome data. We assessed risk of bias (RoB) using the Office of Health Assessment and Translation (OHAT) guidelines. We categorized studies into 3 levels of overall RoB: low, some or high concern. We pooled study results in a random effects meta-analysis comparing average exposure to no-exposure and in a dose–response meta-analysis using all exposure doses. For experimental animal studies, we conducted subgroup analyses for species, Specific Absorption Rate (SAR) and temperature increase. We grouped studies on human sperm exposed in vitro by the fertility status of sample donors and SAR. We assessed the certainty of the evidence using the GRADE approach after excluding studies that were rated as “high concern” for RoB. Results One-hundred and seventeen papers on animal studies and 10 papers on human sperm exposed in vitro were included in this review. Only few studies were rated as “low concern” because most studies were at RoB for exposure and/or outcome assessment. Subgrouping the experimental animal studies by species, SAR, and temperature increase partly accounted for the heterogeneity of individual studies in about one third of the meta-analyses. In no case was it possible to conduct a subgroup analysis of the few human sperm in vitro studies because there were always 1 or more groups including less than 3 studies. Among all the considered endpoints, the meta-analyses of animal studies provided evidence of adverse effects of RF-EMF exposure in all cases but the rate of infertile males and the size of the sired litters. The assessment of certainty according to the GRADE methodology assigned a moderate certainty to the reduction of pregnancy rate and to the evidence of no-effect on litter size, a low certainty to the reduction of sperm count, and a very low certainty to all the other meta-analysis results. Studies on human sperm exposed in vitro indicated a small detrimental effect of RF-EMF exposure on vitality and no-effect on DNA/chromatin alterations. According to GRADE, a very low certainty was attributed to these results. The few studies that used EMP exposure did not show effects on the outcomes. A low to very low certainty was attributed to these results. Discussion Many of the studies examined suffered of severe limitations that led to the attribution of uncertainty to the results of the meta-analyses and did not allow to draw firm conclusions on most of the endpoints. Nevertheless, the associations between RF-EMF exposure and decrease of pregnancy rate and sperm count, to which moderate and low certainty were attributed, are not negligible, also in view of the indications that in Western countries human male fertility potential seems to be progressively declining. It was beyond the scope of our systematic review to determine the shape of the dose–response relationship or to identify a minimum effective exposure level. The subgroup and the dose–response fitting analyses did not show a consistent relationship between the exposure levels and the observed effects. Notably, most studies evaluated RF-EMF exposure levels that were higher than the levels to which human populations are typically exposed, and the limits set in international guidelines. For these reasons we cannot provide suggestions to confirm or reconsider current human exposure limits. Considering the outcomes of this systematic review and taking into account the limitations found in several of the studies, we suggest that further investigations with better characterization of exposure and dosimetry including several exposure levels and blinded outcome assessment were conducted. Protocol registration: Protocols for the systematic reviews of animal studies and of human sperm in vitro studies were published in Pacchierotti et al., 2021. The former was also registered in PROSPERO (CRD42021227729 crd.york.ac.uk = 227729) and the latter in Open Science Framework (OSF Registration DOI doi.org). Excerpts 4.4. Implications for policy and research In conclusion, our systematic review and meta-analyses indicate a possible detrimental effect of RF-EMF exposure on pregnancy rate and sperm count in experimental mammals, whereas the meta-analysis of data on litter size was consistent with null. Although sperm count is not a functional indicator of male fertility, it is a well-standardised analysis routinely applied in clinical andrology. RF-EMF emitting devices are widely applied and epidemiological surveys seem to indicate that, in Western countries, male fertility potential is declining (Auger et al., 2022, Boulicault et al., 2022, Levine et al., 2017). For these reasons the results of our meta-analyses should not be overlooked at a policy level. It was beyond the scope of our systematic review to determine the shape of the dose–response relationship or to identify a minimum effective exposure level. For these reasons, we cannot provide suggestions to confirm or reconsider current human exposure limits. Nevertheless, it is of note that most studies on male fertility, semen quality and reproductive organ toxicity investigated exposure levels which were rather high with respect to those relevant for human populations: 75–80 % tested exposure levels above 0.4 W/kg (ICNIRP basic restriction for workers) and 46–53 % tested exposure levels above 4 W/kg (ICNIRP health effect level) (ICNIRP, 2020). Thus, it is not known the extent to which the conclusions of the SR meta-analysis can be applied to human exposure levels. Similarly, it is unknown how much our conclusion can be extrapolated to frequencies below 100 MHz and above 10000 MHz, for which only very few studies were retrieved. During the systematic review, we identified several methodological limitations in the studies that should be overcome to improve the quality of future research. In particular, blinding during experiment performance and outcome assessment should always be applied to minimize bias, an adequate number of cytological or histological preparations should be analysed, automated methods of analysis should be applied whenever possible, a more standardized and complete reporting of technical methods and results should be adopted. Many studies had to be excluded from the systematic review because of insufficient exposure characterization and a large proportion of included studies were rated at either ‘some’ or ‘high concern’ for RoB for similar reasons. We would recommend that future studies bear the reasons for exclusion or RoB concerns in mind in study design and implementation. There are several papers in the research literature with recommendations on how exposure characterisation concerns can be mitigated, for example Kuster and Schonborn (2000). Finally, studies investigating not just a single level but several exposure levels, spanning from low levels comparable to human exposure to higher levels where mild hyperthermic effects could be expected, should be conducted under the same experimental conditions and target tissue temperature monitoring should be employed. As a final suggestion for future research, we consider it a priority to obtain a scientifically solid database of possible RF-EMF effects on the best predictive surrogate markers of male infertility in experimental rodents. Based on the results of this research, the possibility of testing directly the RF-EMF impact on male reproductive performance could be considered. In view of the limitations of the approach applying in vitro exposure of human sperm, we do not recommend further studies of this kind. Conversely, we suggest exploiting semen quality analysis in human biomonitoring investigations of RF-EMF exposed populations.... Other reviews assessing the impact of RF-EMF exposure on male fertility have recently been published, but these only partially assessed the available literature data (Kesari et al., 2018, Sciorio et al., 2022, Sterling et al., 2022, Vornoli et al., 2019). The few recently published systematic reviews on this topic suffered from some methodological limitations such as the lack of a Risk of Bias analysis (Jaffar et al., 2019, Kim et al., 2021), they limited analysis to only assess effects on semen parameters or were limited to exposure conditions relevant to mobile phone exposures thereby imposing a SAR cut-off (Yu et al., 2021). International committees on human health protection from electromagnetic fields were unable to draw firm conclusions on the possibility of an adverse effect of RF-EMF on male fertility at exposure levels where humans are typically exposed (ICNIRP, 2020, SCENIHR, 2015).... We considered only original, controlled experimental studies published in peer-reviewed journals. We excluded non-experimental studies (e.g., human epidemiologic or other observational studies), and studies of exposure of both males and females of a mating pair (additional decision and change from protocol, see Section 4.5.2). We excluded papers reporting reviews, opinions, proceedings or meeting abstracts. We did not impose any year-of-publication or language restriction.... For each endpoint, we first conducted a meta-analysis of exposed vs sham control comparisons. When a study had several exposure groups matched to the same comparator, the means and standard deviations of these exposed groups were combined into one exposed group using the formulas provided in the paragraph 6.5.2.10 of the Cochrane Handbook (Higgins and Li, 2022), so that each study was entered only once into the meta-analysis. The exposure level assigned to that combined exposed group was calculated as the average SAR of the exposed groups in that study weighed by the number of animals in each exposed group. In the forest plots this is indicated with an asterisk after the study ID. Studies that compared each exposed group to another separate sham control group were entered as separate studies in the meta-analysis. When multiple studies were reported in the same paper, this is indicated with a number after the study ID in the forest plot.... All data subject to a meta-analysis were graphically synthesized by forest plots. A forest plot was drawn in which the studies were divided according to their overall RoB level as “low or some concern” or “high concern”. We decided to exclude from the assessment of the pooled effect sizes the studies rated at “high concern” for RoB in order to draw conclusions based upon the most robust data (see Section 4.5.2).... After reading the full text, 175 papers on animal studies were excluded. They are listed in Supplementary File 1a with a justification of the exclusion rationale together with those not retrieved or not translated. Over 45 % of the animal studies were excluded because essential information was missing regarding exposure set-up and/or dosimetry, e.g., details on how the exposure system output was established and maintained or exposure frequency. A further 27 % of the studies were excluded because outcome data were deemed out-of-scope or invalid.... Regarding studies on human sperm in vitro, we excluded 33 papers after reading the full text (Supplementary File 1b). Most papers were excluded because they did not report peer-reviewed original results. Other papers could not be included in the systematic review because exposure conditions and/or dosimetry were insufficiently reported or because the exposure conditions did not provide a sufficient exposure contrast between RF-EMF exposed and sham-exposed samples.... 4.1. Summary of the evidence and interpretation of the results From experimental animal studies there is moderate certainty of evidence that RF-EMF exposure reduces rate of pregnancy, moderate certainty of evidence that exposure does not reduce litter size, and low certainty of evidence that exposure lowers sperm count. All other results of animal studies and all results on human sperm exposed in vitro have very low certainty. We retrieved few independent studies reporting male reproductive effects after experimental animal exposure to EMP. For this source of exposure, results on pregnancy rate, litter size and sperm count, all consistent with null, have a low certainty. All other results have a very low certainty. It can be asked whether the results of our meta-analyses are consistent with the hypothesis that higher exposure levels, especially those inducing an hyperthermic effect, are more biologically effective than lower exposure levels. The result on the decrease of pregnancy rate is consistent with this hypothesis, as shown by the observation that the pooled effect size is statistically significant only in the subgroup of studies exposed to SAR equal to or higher than 5 W/kg and the statistically significant slope of the linear dose–response relationship. On the other hand, the results on sperm count do not show an increase of the detrimental effect with increasing SAR and all the models of dose–response relationship tested fit the data poorly. Also for other endpoints (the results of which were rated at very low certainty), a direct relationship between the effect and the exposure level is not evident by the subgroup and dose– response analyses and, in some cases, even the possibility of an inverse relationship is suggested by the data. However, this suggestion is not sustained by a solid adverse outcome pathway, and, in some cases, it is based only on few independent studies. We tested if other variables unequally distributed among the subgroups could have a role in increasing the heterogeneity of the observed results and could confound any underlying dose–effect relationship. Indeed, we showed that the absence of blinding during outcome assessment could strongly influence the results for those endpoints that were not measured by automated methods, thus supporting this hypothesis. 4.2. Limitations in the evidence Of all the papers included in the database of animal studies after the title/abstract evaluation, about 60 % had to be excluded for different reasons, with poor exposure characterization accounting for about 45 % of them.... Financial support This project was partially funded by the World Health Organization (contracts 2020/1026306–0, 2022/1275453–1). WHO provided the basis for the protocol and methodological support throughout the review process. Additional in-kind funds were provided by ENEA, Health Canada and Swinburne University of Technology. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments We are grateful to Emilie van Deventer, Maria Rosaria Scarfì and Eric van Rongen for advice regarding the protocols draft and for discussions to ensure consistency in approaches across the multiple ongoing WHO systematic reviews. We wish to thank Flavio Di Marzio for his appreciated graphical help. Open access paper: sciencedirect.com

AI evidence extraction

Main findings

This systematic review included 117 animal studies and 10 studies of human sperm exposed in vitro across 100 kHz–300 GHz (including EMP). Meta-analyses of animal studies reported adverse effects for most endpoints, but not for the rate of infertile males or litter size; GRADE certainty was moderate for reduced pregnancy rate and for no effect on litter size, low for reduced sperm count, and very low for other outcomes. In vitro human sperm studies suggested a small detrimental effect on vitality and no effect on DNA/chromatin alterations, both with very low certainty; EMP studies reportedly showed no effects.

Outcomes measured

• Male fertility outcomes (e.g., rate of infertile males, pregnancy rate, litter size, IVF rate)
• Semen/sperm quality (e.g., sperm count, vitality, morphology, DNA/chromatin alterations)
• Reproductive organ toxicity (e.g., testis/epididymis weight, histology, cell death, histomorphometry)
• Hormonal effects (testosterone)

Limitations

• Most included studies were not rated low risk of bias; risk of bias concerns often related to exposure and/or outcome assessment.
• Heterogeneity across studies; subgrouping by species/SAR/temperature increase explained heterogeneity only in about one third of meta-analyses.
• Too few human sperm in vitro studies to conduct planned subgroup analyses (often <3 studies per group).
• Certainty of evidence was frequently low/very low due to risk of bias, inconsistency, and publication bias.
• Most studies used exposure levels higher than typical human population exposures and guideline limits, limiting applicability to real-world exposure levels.
• Dose–response analyses did not show a consistent relationship between exposure levels and observed effects.
• Very few studies at frequencies below 100 MHz and above 10,000 MHz, limiting extrapolation to those ranges.

{
    "publication_year": 2024,
    "study_type": "systematic_review",
    "exposure": {
        "band": "RF",
        "source": null,
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": null
    },
    "population": "Non-human male mammals (experimental studies) and human sperm exposed in vitro",
    "sample_size": null,
    "outcomes": [
        "Male fertility outcomes (e.g., rate of infertile males, pregnancy rate, litter size, IVF rate)",
        "Semen/sperm quality (e.g., sperm count, vitality, morphology, DNA/chromatin alterations)",
        "Reproductive organ toxicity (e.g., testis/epididymis weight, histology, cell death, histomorphometry)",
        "Hormonal effects (testosterone)"
    ],
    "main_findings": "This systematic review included 117 animal studies and 10 studies of human sperm exposed in vitro across 100 kHz–300 GHz (including EMP). Meta-analyses of animal studies reported adverse effects for most endpoints, but not for the rate of infertile males or litter size; GRADE certainty was moderate for reduced pregnancy rate and for no effect on litter size, low for reduced sperm count, and very low for other outcomes. In vitro human sperm studies suggested a small detrimental effect on vitality and no effect on DNA/chromatin alterations, both with very low certainty; EMP studies reportedly showed no effects.",
    "effect_direction": "mixed",
    "limitations": [
        "Most included studies were not rated low risk of bias; risk of bias concerns often related to exposure and/or outcome assessment.",
        "Heterogeneity across studies; subgrouping by species/SAR/temperature increase explained heterogeneity only in about one third of meta-analyses.",
        "Too few human sperm in vitro studies to conduct planned subgroup analyses (often <3 studies per group).",
        "Certainty of evidence was frequently low/very low due to risk of bias, inconsistency, and publication bias.",
        "Most studies used exposure levels higher than typical human population exposures and guideline limits, limiting applicability to real-world exposure levels.",
        "Dose–response analyses did not show a consistent relationship between exposure levels and observed effects.",
        "Very few studies at frequencies below 100 MHz and above 10,000 MHz, limiting extrapolation to those ranges."
    ],
    "evidence_strength": "high",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "stance": "neutral",
    "stance_confidence": 0.61999999999999999555910790149937383830547332763671875,
    "summary": "This WHO-associated systematic review evaluated sham-controlled experimental studies on RF-EMF exposure and male fertility outcomes in non-human mammals and human sperm exposed in vitro. It reports meta-analytic evidence of adverse effects for many animal endpoints, while finding no effect on infertile-male rate and litter size; certainty ranged from moderate (pregnancy rate reduction; no effect on litter size) to low/very low for most other outcomes. Human sperm in vitro studies suggested a small reduction in vitality and no effect on DNA/chromatin alterations, both with very low certainty, and EMP studies reportedly showed no effects. The authors emphasize substantial methodological limitations and limited relevance of many exposure levels to typical human exposures, and they do not make recommendations about current exposure limits.",
    "key_points": [
        "Searches covered PubMed, Scopus, and EMF Portal up to September 17, 2022, and included peer-reviewed sham-controlled experimental studies.",
        "Included evidence comprised 117 animal studies and 10 human sperm in vitro studies across 100 kHz–300 GHz, including electromagnetic pulses (EMP).",
        "Risk of bias was frequently a concern, especially for exposure characterization and outcome assessment, and few studies were rated low concern.",
        "Animal meta-analyses reported adverse effects for most endpoints, but not for infertile-male rate or litter size.",
        "GRADE certainty was moderate for reduced pregnancy rate and for no effect on litter size, low for reduced sperm count, and very low for other outcomes.",
        "In vitro human sperm studies indicated a small detrimental effect on vitality and no effect on DNA/chromatin alterations, both with very low certainty.",
        "Most studies used SAR levels higher than typical human exposures, and dose–response analyses did not show a consistent exposure–effect relationship."
    ],
    "categories": [
        "Reproductive Health",
        "Male Fertility",
        "Radiofrequency (RF)",
        "Systematic Reviews & Meta-analyses",
        "Animal & In Vitro Evidence"
    ],
    "tags": [
        "Male Fertility",
        "Sperm Count",
        "Sperm Vitality",
        "Pregnancy Rate",
        "Litter Size",
        "Testicular Tissue",
        "Testosterone",
        "In Vitro Sperm",
        "Rodent Studies",
        "Electromagnetic Pulses",
        "Specific Absorption Rate",
        "Risk Of Bias",
        "GRADE",
        "WHO Review"
    ],
    "keywords": [
        "RF-EMF",
        "radiofrequency electromagnetic field",
        "male fertility",
        "sperm quality",
        "rodents",
        "human sperm in vitro",
        "meta-analysis",
        "systematic review",
        "SAR",
        "OHAT",
        "GRADE",
        "pregnancy rate"
    ],
    "suggested_hubs": [],
    "social": {
        "tweet": "Systematic review (117 animal + 10 human sperm in vitro studies) on RF-EMF (100 kHz–300 GHz): animal meta-analyses suggest adverse effects for many endpoints, but not infertile-male rate or litter size. Certainty ranged moderate (pregnancy rate; no effect on litter size) to low/very low for most outcomes; major RoB/heterogeneity limits apply.",
        "facebook": "A 2024 systematic review of sham-controlled experimental studies (117 animal studies and 10 human sperm in vitro studies) assessed RF-EMF exposure (100 kHz–300 GHz, including EMP) and male fertility-related outcomes. The authors report adverse effects in animals for many endpoints, but not for infertile-male rate or litter size, with evidence certainty often limited by risk of bias and inconsistency. Human sperm in vitro findings suggested a small reduction in vitality and no effect on DNA/chromatin alterations, both with very low certainty.",
        "linkedin": "Environment International (2024) systematic review/meta-analyses of RF-EMF and male fertility outcomes in experimental mammals and human sperm in vitro (117 + 10 studies). Reported effects varied by endpoint: no effect on litter size and infertile-male rate, while pregnancy rate and sperm count showed reductions with moderate/low certainty; most other outcomes were very low certainty due to RoB, inconsistency, and publication bias. Authors note many studies used exposure levels above typical human exposures and do not recommend changes to current limits based on this evidence."
    }
}

Comments

Log in to comment.

No comments yet.