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All Deep Dives
Our on-site measurements — and what the science actually says.
SANTA CLARA, California (January 18, 2026) — The internet has lit up with discussion about whether elevated electromagnetic fields at the San Francisco 49ers' practice facility could be a contributing factor to the team's spate of injuries.
Lightwork Home Health visited the area to take readings of the Extremely Low Frequency Magnetic Field strength, or ELF-MF. These are fields frequently generated by sources such as power infrastructure.
Our findings: the fields are 5-20 times higher in certain areas around the facility than in typical residential areas, primarily driven by the transmission lines connecting to the electrical substation; however, we were unable to access the facility itself, and the levels could be much lower inside, or the same or higher.
Near the transmission lines, we observed readings between 4.7 and 22 milliGauss (mG); further from the transmission lines we observed readings of 0.3 to 1 mG, which is typical for most towns and cities.
The scientific literature about the health effects of ELF-MF comes to a variety of conclusions and strengths of evidence. There is, for instance, strong evidence across several meta-analyses for increased risk of childhood leukemia associated with continuous exposure to ELF-MF of 3 mG or more (Seomun et al., 2021; Kheifets et al., 2010) — levels that are exceeded in many locations around the facility.
However, with respect to injuries and musculoskeletal issues at these levels, the evidence is very limited. To be clear: a lack of evidence for ELF-MF causing musculoskeletal issues is not the same as evidence that it has no effect; merely that it has not been studied in depth.
As such, we don't believe that any firm conclusions, positive or negative, can be drawn with certainty based on the current scientific literature (and certainly without readings from inside the facility itself). However, when there is reason for concern — such as an unusual set of injuries and an unusually elevated exposure — we always recommend applying the precautionary principle.
In particular, we would recommend the 49ers test the facility itself. Especially if the levels inside are higher than our external measurements, there could be increased cause for concern and possible remediation. Measurements should be weighted by usage patterns to account for where time is actually spent, and should also account for temporal variation, as the substation and transmission lines’ fields likely vary significantly over the course of the day and the year as power demands cycle.
Remediations for issues of this type range from simple usage pattern changes to more involved active shielding systems, and other options in between.
Lightwork Home Health would be thrilled to work with the 49ers pro bono to do a preliminary evaluation of the facility and help make sure our 49ers’ training environment is setting them up for success.
ABOUT LIGHTWORK HOME HEALTH
Lightwork Home Health provides advanced analysis of indoor spaces. We identify environmental exposures that may be contributing to health concerns — and optimize spaces for wellness and performance. Our comprehensive assessments look at air quality, water quality, light sources, mold, electromagnetic fields, and more, and bridge the gap between these environmental exposures and health outcomes, combining data-driven scientific testing with practical remediation strategies.
Contact: inquire@lightworkhome.com
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