A curious case: a criminal exposure to X-rays

Abstract

In 1989, following a workplace conflict, a worker activated an industrial radiography generator exposing a colleague to a significant amount of ionizing radiation. To our knowledge, this is the only documented case where an X-ray machine was used to commit a criminal act. Since the incident, 35 years have passed. Using the scientific information gathered at the time, we have attempted to create the clearest possible picture of this event. Although scientific knowledge has advanced since then, the overall assessment remains unchanged. An important lesson to be drawn from this crime is the significance of taking early actions to identify the level of exposure and ensure timely intervention to minimize the consequences for the victim. Another takeaway from this event is the numerous challenges the worker faced in having his situation acknowledged by both law enforcement authorities and various government agencies, given the unique nature of the incident.

Introduction

On 18 November 1989, a worker of a nondestructive control company became the victim of aggression using a mobile industrial X-ray machine (Balteau GDF 200/70, 190 kV, 6 mA), while he carried out a weld inspection in a ship’s hull. Before the attack, on 11 November, the perpetrator had previously issued death threats to the victim and to another worker on 15 November. On 16 November, both the victim and his colleague requested not to collaborate with the hostile coworker due to his agressive behavior. Despite this, since he was unable to find a replacement, the employer allowed the assailant to work one last time that night before dismissing him.

On 19 November 1989, the assistant suggested the victim check his dosemeter pen, revealing a dose of 0.6 mSv, while it was normally zero. The next morning, the victim followed the recommandation and observed that it was saturated, indicating a dose greater than 5 mSv. Nevertheless, this was attributed to a possible mechanical shock and he was uncertain if he had reset the dosemeter after calibrating it on 15 November.

On 30 November 1989, Health Canada notified the nondestructive control company that the victim had received a dose of 220 mSv according to his thermoluminescence dosemeter (TLD), initiating an immediate investigation. The victim received this information on 4 December, and the CSST (Commission de la santé et sécurité au travail, Occupational Health and Safety Commission) began an investigation immediately. On 6 December, the Canadian Nuclear Safety Commission (CNSC) instructed the exposed inspector to cease working immediately, and that he could not return without the Commission’s approval.

On 14 December, the company submitted its internal investigation report to the Radiation Protection Bureau (RPB). The report (Fax sent to Health Canada Radioprotection Bureau by the employer Objet: Dosimètre #XXXXXX période #2169 1989-12-14) noted a total of four exposures carried in the work shift, and the incident must have occurred during the second exposure when the safety key was left in the control panel. The company also requested assistance from the RPB to reassure the victim, noting that no skin damage had been detected so far.

An internal note from Health Canada on 4 April 1990, reported a biodosimetric test yielding a dose of 0.06 Gy with an uncertainty ranging from 0.001 to 0.266 Gy. On 3 May 1990, the Health Canada medical consultant, following a phone call, informed the exposed worker of possible health consequences (a slight increase in the risk of cancer) and suggested undergoing a spermogram.

On 24 February 1992, the physicists conducted experiments to recreate the conditions of the accident using X-ray equipment and a phantom. The next day, the trial took place, and the accused was sentenced to 18 months in prison.

On 27 April 1992, a psychological evaluation of the victim noted that he had downplayed the importance of radiation exposure until the trial. However, soon after, he experienced anxiety crises related to the risk of cancer and the possibility of having disabled children partly, in consequence of a doubling of the dose estimation. He also felt guilty for not avoiding conflict with the aggressor and toward his spouse, and exhibited aggression, initially toward the aggressor and later toward his employer. In addition, the psychologist observed a strong sense of being alone in a hostile environment, largely caused by the difficulty he had in getting various authorities to work on his case.

Material and methods

Irradiation geometry of the crime scene

Based on the testimony of various witnesses, the geometry of the scene was reconstructed (Fig. 1). The investigation determined that the X-ray tube could only be operated during the single exposure when the safety key was still in place. The parameters of the radiographic generator (Balteau GDF 200/70) were reported by the victim as 190 kV, 6 mA, and the presumed duration was 220 s, which corresponds to the standard time used for weld quality control.

According to the victim’s testimony, he was positioned 25 cm in front of the X-ray tube, which was 1 m away from the steel sheet making the hull of a ship to be radiographed. The second worker was outside to install the photographic film. For calculation purposes, it is assumed that he was placed 1.25 m from the X-ray tube.

According to the nondestructive inspection company’s internal investigation, the victim’s dosemeters (pen and TLD) were located on his right hip. Additionally, it is believed to have turned to the right at some point to measure the distance between the source and the wall to be radiographed.

Physical dosimetry

Overall, measurements from four dosemeters worn during the incident were available. The TLD was worn at the hip, while the pen dosemeter was worn on the chest. To ease the reading, all doses were converted to mSv and mGy using the conversation factor of 1 R = 10 mGy (unless otherwise stated), following the Canadian National Dose Registry practice. These are reported in Table 1.

Biological dosimetry

In addition to physical measurements, biological indicators were used to evaluate the upper and lower dose limits.

Radiation burn

According to the International Commission on Radiological Protection, transient erythema may appear within hours following exposure for doses exceeding 2 Gy. Persistent erythema may occur after ~10 d for doses exceeding 6 Gy. Dry desquamation may arise from doses around 14 Gy, 4–6 weeks after exposure. Temporary epilation may happen from a dose of 3 Gy, and permanent epilation from 7 Gy onward [2]. Note that these values are thresholds, and in most cases, higher doses are needed to produce a noticeable effect.

The victim measured the distance between the X-ray tube head and the wall. To do this, he had to bring his hand close to it. At 5 cm from the tube head, the dose rate was ~40 Gy/min. Therefore, the risk of radiation burns was significant. There were no detectable signs of radiation burns when the first investigation was carried out. Nevertheless, Kato et al. [3] note that the late erythema can easily go unnoticed, similar to the initial one, especially on the back [4].

Nosebleeds

According to reports from the time, the victim experienced nosebleeds (epistaxis) in the days after the incident. While it could be due to psychological stress, it is also possible that it resulted from a modification of blood formula following exposure to the bone marrow, with a threshold dose of 0.5 Gy [2, 5], as well as local exposures to higher doses [6]. Unfortunately, this cannot be confirmed, since no blood tests were conducted in the following days and months.

Vomiting

Vomiting (emesis) is also associated with acute radiation exposure. It is even possible to obtain a very rough estimate of the dose received based on the time elapsed between exposure and the onset of vomiting [7]. According to the original investigation, recollection of the victims, and press reports, this symptom was not present.

From the relationship presented by Demidenko et al. [7], if no vomiting occurs within the first 24 h, there is a 95% probability that the dose received by the stomach was below 2.8 Gy. However, this value is probably underestimated because the curve appears to be truncated for values greater than 24 h. Indeed, the relationship given by Evans et al. [8] provides only a 10% probability of vomiting within 48 h following exposure to this dose.

In the present case, it is possible that the exposure did not include the stomach and esophagus, as they are located relatively high in the abdomen. Under such conditions, the occurrence of vomiting is unlikely [9].

Dicentric chromosome assay

Unfortunately, it took some time before the victim managed to meet a physicist (J.B.) to help him. During their first meeting, the possibility of doing a biological dosimetry test was proposed. Regrettably, it has been very difficult to have someone provide a prescription for a blood draw. Nevertheless, after some time, it was carried out by a health professional even without a prescription. Unfortunately, this blood sample was poorly preserved, and it was useless for the Health Canada analysis. Therefore, a second professional was searched to carry out a second blood draw. This time the specimen was suitable, and the results were transmitted by the Health Canada Radiation Protection Bureau to the victim on 3 May 1990.

This test yielded a dose of 60 mSv (with a 95% confidence interval ranging from 1 to 266 mSv) according to historical documentation. Unfortunately, Health Canada could not provide further details upon searching their archives. Therefore, we had to rely on retro-engineering of the data to gain insight into the procedure.

A crucial insight is provided in the correspondence between Health Canada and CCSN, where it is stated that the uncertainty calculation procedure was based on the Poisson distribution and utilized the tables of Crow and Gardner [10]. It is also mentioned that if the CNSC deemed it relevant, the laboratory could conduct measurements of 500 or even 1000 cells, indicating that fewer than 500 cells were studied.

Assuming that the upper-bound to central value ratio of the error distribution is 4.43 (266/60), a comparison with Table 1 of Crow and Gardner [10] suggests compatibility with the observation of:

• One cell with a 90% confidence interval (4.532)

• Two cells with a 99% confidence interval (4.36)

• Three cells with a 99.9% confidence interval (4.53)

Based on the modern calibration curve by Beaton–Green et al. [1], an excess of dicentric chromosomes at a rate of 4.23 per 1000 cells is expected for a dose of 60 mSv. Therefore, it is likely that an excess of 1 dicentric per 250 cells was observed. Such a low number of analyzed cells seems to have been in line with the practice of the time, while, today, 1000 cells are usual.

It should be noted that this value is below the threshold limit of 100 mSv generally admitted for this technique [11, 12]. This discrepancy appears to be a consequence of an underestimation of the statistical uncertainties by Health Canada at the time. The most likely culprit is the omission of the uncertainties added by the nonzero value of the number of dicentric when there is no exposure. Using the R package Radir [13, 14], we determined that the probability of the observed dose being below zero was ~25%, assuming zero dicentric as a background and the sample size used. We also confirmed that 100 mSv correspond to a threshold ~95% confidence for 1000 cells analysed using the standard Health Canada calibration curve.

In addition, dicentric chromosomes tend to disappear with time, but the rate of elimination is not well defined in scientific literature. While the International Atomic Energy Agency (IAEA) [12] and Simon et al. [15] recommend a half-life of 3 yr, longer and shorter values have been suggested by various authors. In a study of another suspected overexposure case [16], a metanalysis, based on accessible data from the literature, indicated an exponential decrease following a law with two decay rates, with the faster one having a half-life of 4.8 ± 0.5 months [17].

Although the exact date of blood sampling is undetermined, we do know that the results were available internally at Health Canada on 4 April 1990, ~5 months after the exposure. Therefore, it is likely that the test underestimates the dose by a factor of two. This dose calculation applies to the lymphocyte population, not the whole body [18–20]. In this case, even if the exposure was a few minutes long, most of the lymphocytes are stored in the lymphatic system and move slowly compared to the blood [21], such that only a fraction of them was exposed.

Since the exposure is partial, the dose to the affected organs is necessarily greater than the average dose over the body. Estimating the dose in the irradiated region involves correcting for the fraction of the exposed body. While theoretically possible to statistically detect and correct for partial exposure, in this case, the number of dicentrics observed was too small [12].

Unfortunately, the distribution of the lymphatic system size to the human body is undefined [21]. As a proxy, we used the volume of the irradiated truncated cylinder compared to the whole body volume and the volume of blood contained in the abdominal organs [22]. Both these proxies provide an estimate of ~20% of the whole body volume, resulting in a central value of 600 mSv for the exposed region.

Fertility

Exposure to the testicles on the order of 0.1 Gy can induce temporary sterility, while 6 Gy can result in permanent sterility [2, 23, 24]. After the trial, the victim became very concerned about the consequences of radiation on his fertility and potential genetic damage. To reduce this concern, a spermogram was carried 2.5 y after the incident. After such a long delay, complete recovery following a testicular exposure of 2–3 Gy can be expected [2]. Hence, this test provides no useful constraints.

Dose modeling

Source characterization

The physicists (J.B., L.R.) have characterized the X-ray generator involved in the incident. The dose rate at 1 m from the source for different voltages and thicknesses of copper or aluminum filters was measured. The physicists noted that the half-attenuation layer (HVL) thickness was 0.44 mm for copper at 200 kV, instead of 0.36 mm, as stated in the user manual, indicating more penetrating radiation. The HVL for aluminum at 190 kV was determined to be 7.5 mm (see Table 2).

Another test was conducted to quantify radiation transmission through a steel plate like the one that was inspected during the incident. The measurement was taken at 1 m from the tube. This data was used to calculate the exposure of the assistant who was positioned behind this plate, outside the ship’s hull (Table 3).

To map the shape of the beam, a film cassette (14″ × 17″) was placed 25 cm away from the X-ray tube outlet (Fig. 2). The half-angle of the exit was 30.5° horizontally and 24° vertically and took the form of a truncated ellipse, which was consistent with the specifications given in the user manual.

Constrain on models

From the dosemeter measurements, it is possible to calculate the exposure times by the radiation source. For the TLD dosemeter worn by the victim, the maximum dose rate at 25 cm is 133.6 R/min. Therefore, the maximum duration of direct exposure time cannot exceed 10 s; therefore some shielding by the body or some displacement outside the beam must have occurred.

For the TLD dosemeter worn by the assistant standing behind the steel plate, the minimum exposure time is ~17 s (60 mR at 0.21 R/min). This provides support to the scenario that the victim stayed in the beam and shielded the second worker for the whole exposure.

Dose on an anthropomorphic phantom

To better assess the dose received, an anthropomorphic phantom was employed. Its diameter was 32 cm, and its surface was placed 25 cm from the tube, the same position as the victim, and exposure measurements were taken with the same operating parameters as during the incident (190 kV, 220 s) (see Fig. 3).

The detectors were placed at different locations in the phantom. Point A′ is at the surface of the detector directly exposed to the X-ray tube. Its measurement is therefore representative of the maximum skin dose. Detector C′ corresponds to the surface of the skin perpendicular to the beam and thereby approximately coincides with the position of the dosemeter. Detectors A, C, and F are located 1 cm below the surface. Detector D is at the center. Detectors B and E are placed on a line at a 45° angle from the radiation axis, on a circular arc of 10.5 cm. The doses measured on the phantom have been converted from R to Sv using the conversion coefficient 1 Gy = 104 R [25](Table 4).

Dose derived from a model

In addition, a digital phantom retaining the same geometry was employed to assess exposure [26]. The primary limitation of this model was its maximum allowed voltage of 120 kVp, which would likely lead to an underestimation of doses due to a less penetrating beam. It is noteworthy that this constraint is common in most models, as higher voltages are not typically used in medical imaging for which they are designed.

The parameters utilized were:

• Source-to-skin distance: 25 cm

• Skin dose: 489 R at 25 cm

• Rectangular field dimensions: 118 × 90 cm² at 1 m or 29.5 × 22.5 cm² at 25 cm

• Half-value layer (HVL): 7.5 mm

• Vertex distance: 75 cm.

The results of this model are presented in Table 5. At one point, we considered recalculating the doses using more modern software (e.g. Geant 4). However, we concluded that such an approach would not yield additional precision due to uncertainties in the initial parameters.

It is important to note that using a rectangular field instead of an elliptical one increases the total dose by ~25% compared to the approximately elliptical field of the x-ray beam. However, since the voltage used by the equipment significantly exceeds that of the model, this would result in an underestimation of the dose. Therefore, the discrepancy of the irradiation beam between the exposure and test geometry balances out the discrepancy of the applied tube voltage in terms of organ does. Of course, this also adds a source of uncertainties.

Based on this analysis, the absorbed dose in the bone marrow is 934 mGy, while, for the abdominal region, it is 870 mGy, and the dose to the testicles is 117 mGy. The effective dose using the publication 103 of the International Commission on Radiological Protection (ICRP) weight is 438 mSv [23].

Discussion

The dose measured by the dosemeter during the accident is 220 mGy, which is less than the 420 mGy observed on the skin of the phantom. It is probable that the dosemeter was either more protected by the body or moved out of the radiation zone for part of the time. It is also possible that the distance to the emission source was slightly greater than the 25 cm used for the simulation. In addition, this might be caused by the discrepancy between the model and the X-ray beam characteristics.

The absorbed dose can be roughly calculated using the phantom data and these can then be compared to the detailed model. In the abdominal region, the arithmetic mean of the doses obtained on the phantom is around 1.1 Gy (0.7 Gy for the harmonic mean), while the mathematical model gives 870 mGy, which is consistent with the phantom measurement.

The amount of active marrow in the lumbar vertebrae is 11.7% in a 25-year-old individual [2, 27]. Assuming they received 6 Gy (point A), the corresponding dose averaged over the whole mass of bone marrow would have been 700 mGy. The pelvic bones (ilium) might also have been affected. These contain 19.5% of the active marrow. Using the dose measured by the dosemeter of 220 mGy, this adds 43 mGy to the average marrow exposure. The sacrum could also have been affected (9.4% of the marrow, 19 mGy). These components add up to an average dose to the bone marrow of 760 mSv, while the mathematical model obtains a dose of 934 mSv, which is a rather good agreement considering all the uncertainties involved. Note that both these values are above the acute radiation exposure threshold of 500 mGy [2].

By weighting the absorbed doses by the fraction of the blood volume contained in the exposed organs [2], an average blood dose of 120 mGy is obtained, which is consistent with the value deduced by biodosimetry if dicentric population decay is considered.

The measurement at point D of the phantom is probably the maximum dose that the testicles could have received (580 mGy), while the model gives 117 mGy, which is closer to the dose at point E (140 mGy).

The body attenuation obtained from the ratio of doses at points A and F, correcting for geometry, is approximately a factor of 39. This would give a minimum exposure time of 663 s to obtain the dose observed on the assistant’s dosemeter. Given that the victim’s position was not necessarily central, and the victim may have rotated at some point, this value is compatible with the scenario in which the victim remained in front of the target for practically the entire exposure period.

Therefore, the reconstruction using a phantom and the mathematical model is broadly consistent with each other and with biodosimetry. All support the model where the victim stayed in the beam for the entire duration of the exposure.

Expected consequences

Psychosocial

At first, the victim was a little concerned about the effect of radiation but was highly frustrated with not being able to get any support from the authorities. This was amplified by the employer’s downplaying of the incident and the first policeman’s refusal of assistance, as well as the misunderstanding of the employee of the CSST who seemed overwhelmed by this atypical case. This situation led the victim to isolate himself but also to develop aggression to assert the validity of his case. In addition, he chose to leave his job because he felt that the radiation dose received exceeded what was expected over a full career. His psychological health deteriorated until his case was taken over by a physicist and a policeman, as well as through the justice system. This delay before the intervention of an expert had an amplifying effect on his risk perception [28].

Unfortunately, while the trial provided justice, the recreation of the accident by the physicists made him realize that he had been exposed to about twice the dose than he had originally believed. According to the victim’s psychological assessment report produced after the trial, he suffered a profound psychological shock at that moment. While his previous concern was to get justice, from then he then developed a very strong fear of having cancer and passing on genetic problems to his children.

This reaction was predictable. Accidental exposure to high-level ionizing radiation is one of the most traumatizing experiences. Since it is an invisible, odorless, and colorless threat, and its effects can be felt over a very long term, it is a truly terrifying experience [29, 30]. For example, during the radiological accident in Goiânia, ‘The fear was so intense that some people fainted in line as the time for examination approached,’ reported the psychologist Ana Bandeira de Carvalho [31]. A significant number of people also showed stress-induced symptoms that mimicked radiation exposure (fatigue, nausea, vomiting, diarrhea, or skin redness) [31]. Even radiographers [32] or doctors [31, 33] can lose their composure, suffer psychological distress, or even panic during a radiological incident if their radiation protection training is insufficient.

Paradoxically, a high level of education without adequate knowledge of radiation effects tends to increase rather than mitigate the detrimental psychological consequences [31].

From past nuclear disaster experiences, it was concluded that many health issues were probably not due to radiation exposure but rather to anxiety about the possibility of developing subsequent illnesses. This chronic anticipation of negative outcomes led individuals to interpret seemingly minor physical sensations as symptoms of illness, perceive their current health as poor, and their future health as bleak.

A seminal case is the Estonian cleanup worker at Chernobyl. While the doses they received were relatively low (average ~100 mSv), they did present an increased risk of suicide and an increase in alcohol and tobacco-related cancer [34, 35]. In the context of the Fukushima nuclear accident, it has been shown that negative psychosocial impacts on health and well-being far outweighed those of radiation exposure [36–38]. Therefore, cases of radiation exposure must be promptly addressed by specialists to minimize negative psychological impacts [39, 40].

Additional cancer risk

Around the same time as the accident, Publication 60 by the ICRP [41], which tightened radiation protection standards, was released. This was later followed by the Canadian government’s own safety standard. This action has been rightly interpreted as an admission that the risk of radiation exposure had been underestimated in the past.

While individual risk calculation from epidemiological data is not recommended in a clinical setting, it is often needed in court for the damage evaluation. At that time, the physicists’ report included an estimate of the risk of fatal cancer based on Table B-9 from ICRP Publication 60 [41] (0.092/Sv for a man exposed at 25 y old), as well as a specific report on radiation-related injuries produced by LR. Using a reference dose of 500 mSv, LR had established the excess risk of death from cancer at 4.6%.

We have recalculated this expected future excess risk using modern epidemiological tools. Specifically, we employed the RadRAT software developed by the National Institute of Cancer in the United States [42]. This software relies heavily on the epidemiological model from the BEIR VII report [43], which itself draws on the cancer epidemiology data from the victims of the atomic bombings of Hiroshima and Nagasaki.

As model parameters, we used American epidemiological data for white men from 2000 to 2005. This involved some epidemiological transfer procedure that make use of the excess relative risk models and excess absolute risk models [42].

The year of birth was set in 1963, the exposure date was set in 1989, and acute exposure was selected due to the dose rate. The future excess risk was calculated from 1989 and from 2024 until the end of expected lifetime. Our projection is based on the various doses to organs assessed by the digital phantom displayed in the original physicists’ report, without correction for geometry. Results are presented in Table 6.

The total additional relative risk from 1989 over the lifetime is estimated at 9%, corresponding approximately to an excess probability of mortality of 4.5%, assuming a survival rate of 50% for cancer. Remarkably, this value closely aligns with the original evaluation, despite differing initial assumptions. Note that the probability of death from a cancer is related but distinct from the detriment that also takes account of other factors [44]. In terms of additional absolute risk, colon, bladder, prostate cancers, and leukemia are the most important.

Between 1989 and 2024, the absolute risk of excess cancer until the expected end of lifetime decreased by an average of 17% since the accident. For one of the main cancer risks, leukemia, the reduction is even more pronounced (−35%), as this is short-latency cancers that have a substantial probability of having already arisen.

Until now, the worker did not suffer from any cancer in the abdominal region. However, if this were to occur, the probability that the cancer was caused by radiation exposure would be significant. It would then be appropriate to calculate the radiation-attributable fraction for litigation purposes. These calculations are beyond the scope of this paper but we refer the reader to the IAEA documentation [45–47]. Additionally, it is worth mentioning that the worker developed an acoustic neuroma a few years ago, which is highly unlikely to be related to the radiation exposure received at work.

Genetic

A specific fear expressed by the worker, a young man at the time, was that his future offspring would suffer from genetic illnesses due to radiation exposure [28, 48]. Although this fear is present in many accidental overexposures, it is essential to understand the historical context that made it even more significant. Indeed, during the same period, newspapers were reporting concerns about an excess of infant malformations near the Gentilly nuclear power plant in Quebec, the Pickering plant in Ontario, and Sellafield in Britain, which lent credibility to this potential threat.

This concern traces back to classic experiments by Herman Muller, demonstrating that radiation could induce hereditary genetic effects on the offspring of Drosophila melanogaster [49]. Starting in 1947, significant studies were conducted on mice as part of the Mammalian Genetics and Genomics program at Oak Ridge Laboratories. Under the direction of William and Lianne Russell, the ‘megamouse’ research exposed hundreds of thousands of male mice to ionizing radiation to examine mutagenic effects on their progeny and assess the human genetic consequences of low-dose exposure. Simultaneously, the British Mouse Genetics Project began in Edinburgh under C. H. Waddington’s leadership. By the mid-1950s, the group had moved to Harwell, where they bred and studied 150 000 mice [50, 51].

While these experiments clearly demonstrated hereditary effects in mice, the situation was different for human populations exposed to radiation. Over time, the estimation of the contribution of hereditary effects to radiation-induced harm diminished, decreasing from 100% in 1954 to 4% in 2007 [52].

One of the most studied populations on the hereditary consequences of radiation exposure is the Hiroshima and Nagasaki populations. During the initial decade after the atomic explosions, most concerns regarding long-term health focused on potential hereditary genetic impacts in subsequent generations. At that time, little attention was given to long-term somatic effects, including cancer, due to their delayed onset [53]. While transgenerational risks were considered significant at the time of the accident, current studies suggest that human health is not significantly affected by the transgenerational effects of radiation [54–56].

Recent epidemiological results on the descendants of this population show no detectable effect on mortality from exposure by either parent [57, 58]. Moreover, no relation was found between paternal or maternal radiation doses, their cumulative doses, and an increased risk of multifactorial diseases. None of the 18-radiation dose-response slopes, adjusted for other risk factors, were statistically significant. However, the studied population is still in midlife (average age of 48.6 y in 2013), and much of the incidence of multifactorial disease will manifest in the future. Continuous longitudinal follow-up will provide improved risk estimates for hereditary genetic effects on adult-onset multifactorial diseases [59, 60] or cancers [61].

Moreover, no significant genetic effects have been observed in the descendants of this population [62–66] analyses indicated an increased risk of major congenital malformations and perinatal death, but the estimates were imprecise for direct radiation effects; most of them are not statistically significant, although all were positive. The analysis of this population allowed estimating the doubling dose of genetic effects from 1.7 Sv to 2.2 Sv [67]. However, Sankaranarayanan and Chakraborty [68] obtained 0.82 Gy but recommended the value of 1 Gy to avoid creating an impression of precision. This value was adopted by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) [69] and ICRP [23]. While transgenerational risks were considered significant at the time of the accident, current studies suggest that human health is not significantly affected by the transgenerational effects of radiation [54–56].

Transgenerational effects might be limited to relatively short periods after exposure, likely to be rare in humans [70–72]. Thus, mutations induced in later stages of spermatogenesis will only affect sperm production for ~3 months, while those induced in spermatogonial stem cells will continue to produce mutation-carrying sperm throughout.

In addition, recent advances in genetics demonstrated the number of natural de novo mutations increases exponentially with the age of the father with an approximate doubling time of 20 y [73]. In this case, assuming a dose of 140 mSv to the testicles, this would have been the equivalent of delaying the conception of a child by 1.5 y.

Root cause analysis

To better understand the causes of the accident and learn valuable lessons, we used various analysis tools:

• (1) Causation Tree: The cause tree aims to establish the sequence of events leading to the accident or incident. Its goal is to identify both proximal and latent causes, allowing us to identify preventive measures that could have been taken. It is based on the methodology developed by the French Institut National de Recherche et de Sécurité [74].

• (2) Haddon’s Matrix: Has been created by William Haddon Jr. in the 1970s, Haddon’s Matrix is a conceptual tool used to determine the best approaches for reducing both the occurrence and consequences of accidents. Originally employed in the context of highway safety, it later introduced a list of 10 countermeasures applicable to risk reduction [75, 76]. Haddon also proposed a methodology for identifying the optimal action strategy [77, 78].

• (3) Human Error Model: Approximately 20% of accidents have material causes, while 80% primarily result from human factors. However, upon closer examination, most human errors stem from latent organizational problems, with only 30% directly attributable to individual actions. In such conditions, fingering a single culprit does not lead to significant improvements in operational safety [79]. Instead, understanding why persons acted as they did is essential for prevention [80]. The U.S. Department of Energy has developed an algorithm for this purpose [79]. An alternative approach is the Swiss Cheese Model [81], which postulates that accidents occur when multiple safety barriers align in failure modes.

From our analysis using these tools, we have identified some obvious elements:

• The aggressor’s state of mind was inadequate for operating a radiation source.

• Leaving the safety key in place allowed the attack to happen.

However, a deeper analysis reveals additional issues:

• Although workers had noticed their colleague’s mental health problems, the administration failed to act promptly. Human resource management within the company was inadequate, as it struggled to find a replacement worker quickly, while the victim succeeded in finding someone to assist him.

• The stress induced by the aggressor’s presence contributed to forgetting the safety key.

An additional lesson was the deficient postaccident response. Both the company and civil society proved incapable of adequately reacting to the accident. Efforts seemed focused on minimizing it rather than implementing measures that could significantly limit its impact.

Recommendations

Although 35 y have passed since this accident, the lessons that can be drawn from it remain relevant.

The first recommendation is to quickly involve radiation effect specialists to take charge of the victim. Any delay causes unnecessary anxiety, which itself can have deleterious effects on the patient, often exceeding the effects of radiation if not treated correctly. It is worth noting that the victim, decades after the incident, considered the intervention of a physicist in managing his case as a decisive step in regaining control of his life.

Moreover, this intervention must be accompanied by numerous physical tests to confirm or refute the impacts of the radiation dose. Finally, it is essential not to forget that the risks of deleterious stochastic effects of radiation are permanent. Therefore, the patient must be monitored for the rest of their life to prevent adverse health developments. While there is no prescription for the best approach for monitoring, it is likely that non-invasive measures not involving ionizing radiation should be favored (Ex. skin cancer screening in the exposed region).

These preventive measures are particularly important for the psychological being of the victim. While it is impossible to eliminate the damage caused by radiation, there are plenty of ways to reduce risk from other sources by having a healthy lifestyle [82]. This is a fact that should be emphasized as a tool to regain control.

Acknowledgements

We would like to thank Dr. Alice Turcot from the Services en santé au travail, Direction de santé publique, CSSS de Chaudière-Appalaches, Québec and Ruth Wilkins, Ionizing Radiation Health Sciences Division Health Canada for their help while seeking the original documentation. We are indebted to reviewer 2 for his rigorous work that led to a significant improvement in our paper.

Author contributions

The effort on this paper was spread over 35 years. The original work was carried out by J.B and L.R., while writing the present article and integrating modern literature was carried out by Y.D. and F.N. Conceptualization J.B., L.R., Y.D.; Methodology, J.B., L.R., Y.D.; Software, L.R., Y.D.; Validation, J.B., L.R., F.N.; Investigation: J.B., L.R., Y.D.; Ressources, J.B.L.; Writing—Initial Draft, J.B., L.R., Y.D.; Writing—Review & Editing, Y.D., J.B., L.R., F.N.; Visualization J.B., Y.D.

Funding

None declared.

Conflict of interest

None declared.

References