Burns Resulting From Electric Vehicle Manufacturing in Silicon Valley

Abstract

The development of electric vehicles (EVs) has introduced novel technologies and manufacturing processes that expose workers to new risks of burn injury. We identified 6 patients who were admitted to our burn center for injuries that occurred while working in EV manufacturing facilities. The burns fell into 3 categories: flash flame burns due to lithium-ion battery explosions, high-voltage electrical injuries, and burns caused by contact with molten metal. Recognizing these recurrent patterns of injury should inform future prevention efforts and prepare health systems to evaluate and treat patients burned in EV manufacturing.

INTRODUCTION

The past decade has seen rapid development and widespread adoption of battery-powered electric vehicles (EVs) without general recognition of the occupational hazards involved in their manufacture. Since 2010, car builders have increasingly replaced their gasoline-powered fleets with hybrid or all-electric platforms; Tesla’s Model Y was the best-selling new car in the world in 2023. While automotive electrification promises to reduce the rate of global fossil fuel consumption, the high-voltage batteries and electrical systems that power EVs raise questions about vehicle safety. In addition to the road users and emergency responders affected by fires caused by EV collisions, the employees who build and test new EV technologies face health hazards distinct from those encountered by previous generations of automotive workers.^1,2

We present our experience caring for workers burned during the manufacturing of EVs. While safety concerns surrounding lithium-ion batteries are well-documented, no study has described injuries to individuals harmed by battery explosions and malfunctioning EV components. Santa Clara Valley Medical Center—the only combined burn/trauma center in the San Francisco Bay Area, located at the epicenter of EV development—has cared for a series of patients who were burned while working in EV factories. Our goal in reporting on these injuries is to describe the recurrent causes of burns specific to EV manufacturing and convey the gravity of this new occupational risk to the automotive industry and the public.

METHODS

Following institutional review board approval, we performed a retrospective review of a prospectively maintained database of all patients admitted to our burn center for work-related injuries between January 2013 and December 2023. Using self-reported employer information, we identified patients who were injured while working at a company that exclusively manufactures EVs. We collected information on patient demographics, mechanism of burn, percent total body surface area (TBSA) burned, nonburn injuries, surgical operations, length of stay (LOS), and return to work. We did not include patients burned in motor vehicle collisions or other nonwork-related accidents involving EVs. We also did not include patients with less severe injuries who were seen in the Emergency Department or in the outpatient clinic but never admitted to the burn center.

RESULTS

Six patients were admitted to our burn center for injuries sustained while working in EV manufacturing plants. All were male and between 23 and 36 years of age (average 30.8 years) at the time of injury. Three patients were Asian, 2 were Hispanic, and 1 patient was Black. Three patients were burned by lithium-ion battery explosions (Figure 1), 1 patient suffered a high-voltage (>500 V) electrical injury (Figure 2), and 2 patients were burned by contact with molten aluminum alloy (Figure 3). Two patients were intubated for airway protection and 2 patients were found to have corneal burns (Table 1).

Figure 1.

Patient 1 Was a 30-Year-Old Male Who Sustained Near-Circumferential Second-Degree Burns to the Right Upper Extremity as a Result of Lithium-Ion Battery Explosion (A). He Healed Without Surgery and Had Not Developed Significant Scar Contracture at His 1-Month Follow-Up (B)

Figure 2.

Patient 4 Was a 36-Year-Old Male Burned by Contact With a High-Voltage Electrical Cable Resulting in Full-Thickness Burns to the Face, Neck (A), Chest, Abdomen, and Bilateral Upper Extremities (B, C). He Required Forearm Escharotomies on Arrival (B, C) and 10 Rounds of Debridement and Skin Grafting Over the Next 2 Weeks, Including Sheet Grafting to the Neck and Both Hands (D), as Depicted on Postburn Day 20. His Right Small Finger Was Nonviable and Amputated, But Scars to the Hands (E) and Neck (F) Healed With Minimal Contracture, Pictured at 2 Years Postburn

Figure 3.

Patient 6 Was a 31-Year-Old Male Who Was Burned by Molten Aluminum Alloy During the Die-Casting Process. He Sustained Full-Thickness Burns to the Trunk, Pictured on Arrival (A) and on Postburn Day 4 (B), Bilateral Hands (C), and Bilateral Legs. The Burns Were Reconstructed Over the Course of 5 Operations; Sheet Skin Grafts Were Applied to the Hands (D), Meshed Skin Grafts Were Used to Cover the Other Burns, Including to the Upper Arms (E), Pictured on Postburn Day 12

Table 1.

Patient Characteristics and Injury Presentation

	Age (years)	Gender	Race	Burn mechanism	Etiology	Noncutaneous findings	Endotracheal intubation (yes/no)
Patient 1	30	Male	Asian	Flash flame	LIB explosion		No
Patient 2	23	Male	Asian	Flash flame	LIB explosion	Bilateral corneal burns	No
Patient 3	33	Male	Hispanic	Flash flame	LIB explosion	Bilateral corneal burns	No
Patient 4	36	Male	Asian	Electrical	High-voltage cable	Mild creatinine kinase elevation	Yes
Patient 5	32	Male	Black	Contact	Molten aluminum alloy		No
Patient 6	31	Male	Hispanic	Contact	Molten aluminum alloy		Yes

Abbreviations: LIB, lithium-ion battery; LOS, length of stay.

Burned TBSA ranged from 2% to 30%, with an average of 11.5% (SD = 12.6%). Five of the 6 patients were burned on the extremities, 3 suffered facial burns, and 3 patients were burned on the trunk. Three of the burns were second-degree (ie, partial skin thickness), 1 was third-degree (ie, full skin thickness), and 2 were fourth-degree (ie, extending to deep subcutaneous adipose tissue). Three of the 6 patients required surgery for their burns. Among the patients who underwent surgery, the mean grafted area was 1791.3 cm² (SD = 1810.2 cm²) over an average of 5.3 operations. None of the patients died as a result of their burns. LOS ranged from 1 to 42 days with an average of 14.7 days (SD = 14.8 days). All patients returned to employment within 10 months of injury; 5 of the 6 patients returned to work within 5 months of their burns (Table 2).

Table 2.

Burn Characteristics, Surgical Details, and Outcomes

	Percent TBSA	Greatest degree	Involved areas	Number of operations	Total grafted area (cm2)	Nongrafting procedures	LOS (days)	Return to work (months)
Patient 1	5	Second	RUE	0			11	3
Patient 2	2	Second	Face, BUE	0			1	1
Patient 3	5	Second	Face, BUE	0			7	1
Patient 4	30	Fourth	Face, neck, chest, abdomen, BUE	10	3651	BUE escharotomies, finger amputation, hand scar release with LTR	42	10
Patient 5	2	Third	Abdomen, genitals	1	35		7	2
Patient 6	25	Fourth	Abdomen, buttocks, BUE, BLE	5	1,688	Finger debridement, hand scar release with LTR	20	5

Abbreviations: BLE, bilateral lower extremities; BUE, bilateral upper extremities; LTR, local tissue rearrangement; RUE, right upper extremity; TBSA, total body surface area.

DISCUSSION

Our series revealed novel patterns of injury and morbidity in EV manufacturing that have not been described in traditional automotive buildings. Car manufacturing has represented a significant source of burns for more than a century; historically, those injuries fell into 3 distinct categories: radiator fluid scald burns, contact burns due to hot engine or exhaust parts, and flame burns related to accidental gasoline ignition.^3,4 Burn specialists rely on associations between described mechanisms and specific injury patterns to inform early management (eg, fasciotomy for high-voltage electrical injury) and set expectations for burn depth, need for surgery, and timing of recovery. Radiator fluid burns, for example, are scalds that often affect the dominant hand and arm but may be relatively superficial, while carburetor-related flame burns are typically deep and often involve the face and neck, frequently prompting early endotracheal intubation due to airway edema.^3,5–10 Understanding the inciting mechanisms and physiologic characteristics of each type of burn is, therefore, critical to efficient, anticipatory management of these patients.

Electric vehicles account for a rapidly growing share of the automobile industry. In 2023, nearly 1 million EVs were sold in the United States, which included 21.5% of all cars sold in California.¹¹ This trend became apparent in our burn center more than 10 years ago when patients began to present with injuries related to the early development of EVs in our region. While EV collisions did not seem significantly more dangerous than those involving gasoline-powered cars, we were concerned about a series of patients who sustained burns while working in EV factories. The severity of these burns and our unfamiliarity with the mechanisms by which they occurred prompted us to study the risks involved in EV manufacturing.

There were similarities between the patients in this report and those described in previous studies on traditional automotive burns. All the patients in our study were men in their 20s or 30s, consistent with literature showing that young males are almost exclusively at risk for burns related to vehicle manufacturing and maintenance.^3,5–10 Burned percent TBSA and LOS were also not dramatically different from prior studies on automotive burns, though rigorous analysis was not possible with our small sample size. Like radiator and carburetor burns, the burns in our series frequently affected the upper extremities and face, reflecting the nature of manual mechanical work.

Most of the burns in our cohort were severe and disabling. Three of the 6 patients in our study required surgery and 5 sustained significant hand and forearm burns. Two of those patients developed hand contractures, necessitating surgical burn scar release and intensive postoperative rehabilitation. Among a group of young, productive individuals, these injuries were especially devastating and delayed their return to work. Interestingly, the characteristics of the burns varied widely according to etiology. Like the automotive burns of last century, we found that EV-related injuries could be sorted into 3 categories based on mechanism: lithium-ion battery explosion flash flame burns, high-voltage electrical injuries, and burns caused by contact with molten metal.

Lithium-ion batteries have been fundamental in the development of handheld electronics and EVs, providing high energy density and long lifespan characteristics unmatched by other forms of portable energy storage. Their rapid commercialization has been accompanied by safety concerns related to the flammability of their chemical components.^12–14 Put simply, when lithium-ion batteries are exposed to high-temperature and high-voltage conditions, the decomposition of component materials may result in a phenomenon called thermal runaway, which can lead to battery rupture and explosion.^12,13 This is particularly problematic in EVs given the size of their batteries and the high-output currents used to charge. Moreover, flash flames generated by batteries represent electrical discharges, which can transmit current like electrical arcs, such as lightening, compounding the thermal energy delivered by all flames.¹⁵ Simulation of extreme operating conditions is essential to the testing of lithium-ion battery systems and may have contributed to the explosions that injured 3 of the patients in our study.¹⁶ Each of the 3 patients described an unexpected explosion that occurred while manipulating a lithium-ion battery, resulting in a flash flame burn to the upper extremities. Two of the 3 patients also suffered facial burns and associated corneal injuries. Fortunately, lithium-ion battery-associated injuries appear to be relatively mild in this context due to the transient nature of flash flames; none of the lithium-ion battery burns at our center was full-thickness or required surgery; none involved a chemical injury. It should be noted that fires caused by lithium-ion battery rupture burn hotter and longer than traditional vehicle fires and are likely to cause more severe injuries in the setting of prolonged exposure.²

One patient in our cohort suffered electrical injury when he simultaneously touched a ground cable and live wire during EV assembly. Most EV batteries operate at a voltage of 300–800 V and can achieve a maximum current of about 1500 A; our patient’s burn, which extended from the hands to the head and trunk, was consistent with high-voltage (ie, >500 V) injury.¹⁷ EV batteries deliver direct current to an inverter, which passes the electricity to one or more motors in the form of alternating or direct current, depending on the vehicle model. In general, electrical injuries occur when a complete circuit is created between a live contact and a ground with human tissue intervening, as occurred in this case. While voltage is widely used to categorize electrical burns, it should be mentioned that the level of tissue necrosis is dependent on the current (current = voltage/resistance; Ohm’s law) and duration of electricity delivery, which may be difficult to ascertain in many cases.¹⁸ Passengers are isolated from the live electrical components in EVs, and the risk of electrical shock appears to be minimal, with very few reported cases of electrical injury occurring during normal operation. The danger to workers who build or service EVs, however, is significant, and physicians who encounter these patients should consider the manifestations of high-voltage electrical injury, which include cardiac arrhythmias, myonecrosis, compartment syndrome, central nervous system derangements, and hidden tissue damage distant from contact points.¹⁹ Our patient presented with a mild, transient elevation in creatinine kinase and no cardiac enzyme or electrocardiographic changes but sustained deep thermal trauma to his face and upper extremities, necessitating intubation and emergent escharotomy. He ultimately required finger amputation and developed scar contractures in both hands, which improved over the course of 10 operations.

Finally, the reliance of EV manufacturers on die casting to produce metal components exposes workers to increased risks of high-temperature contact burns. Die casting describes the process of feeding molten alloy into a mold at high pressure and high speed to create metal parts. Relative to other manufacturing methods, aluminum alloy dies casting produces strong, lightweight components that have excellent thermal and electrical conductivity.²⁰ Because of these properties, aluminum die-cast parts have been extensively integrated into the production of EVs, which are afflicted by high curb weights and battery-generated heat. While die casting has been used to make select parts in gasoline-powered cars for decades, Tesla introduced the first large-scale high-pressure casting system in 2020 with its “gigacasting” technology, which allowed for the casting of the entire rear structure of its vehicles in 1 piece.²¹ Other EV companies have followed suit. Two patients were admitted to our burn center after being sprayed with pressurized hot aluminum alloy during the die-casting process at EV factories. The mechanism was identical in each case, and while 1 patient sustained minor injuries, the other required 5 operations for deep 25% TBSA burns and developed persistent hand scar contractures that required multiple surgical releases. The melting point of aluminum is over 600 °C, and combined with the pressurization required for die casting, it presents the potential for devastating burns. The paucity of previous reports on injuries related to die casting suggests that the novel alloys and processes being employed by EV companies may be outpacing historical safety measures.

For decades, researchers have studied automotive workers and suggested approaches to preventing common types of vehicle-related burns. In 1990, Abidin et al. published about the dangers of carburetor priming and suggested adding warning labels and backfire flame arrestors to engine compartments as featured on some power boats.²² Rabbits and colleagues used their 2004 study to petition the Department of Transportation to mandate radiator cap modifications similar to child-safety lids.⁵ While efforts to prevent automotive burns through research have had mixed results, reporting on the health risks posed by common manufacturing processes is an essential first step in advocating for safety-focused regulatory changes. Continued investigation into injuries that occur repeatedly during EV manufacturing is critical to improving the safety of automotive workers. Moreover, physicians who understand the mechanisms of burns that occur during EV manufacturing will be better prepared to evaluate and treat affected patients.

Author Contributions: Max L. Silverstein (Conceptualization [equal], Data curation, Formal analysis [lead], Investigation, Methodology [equal], Project administration [lead], Resources [supporting], Writing—original draft [lead], Writing—review & editing [supporting]), Yvonne Karanas (Conceptualization [equal], Data curation [supporting], Investigation, Methodology, Resources, Supervision, Writing—review & editing [equal]), and Clifford C. Sheckter (Conceptualization [lead], Data curation [supporting], Investigation, Methodology, Resources [equal], Supervision, Validation, Writing—review & editing [lead])

Funding: Dr. Sheckter is supported by a grant from the National Center for Advancing Translational Sciences of the National Institutes of Health under award number KL2TR003143. The authors have no other financial disclosures to report.

Conflict Of Interest Statement: The authors have no conflicts of interest to report.