Part 11 of 13 in Thirteen Records. The long article, Data Centers Don’t Have an Environmental Record. They Have Thirteen of Them., rates thirteen kinds of environmental complaint against data centers. This series takes them one at a time.
I work at a local ISP in Northern Illinois and co-founded FD-IX, an internet exchange. I have no customer, vendor, or interconnection relationship with any facility or developer named here and no financial position in any of them beyond broad-market index funds. My industry grows with infrastructure investment in a general way, which is an indirect interest; the full disclosure is at the top of the complete article.
The physiology is not in dispute. Light at night suppresses melatonin, disrupts circadian rhythm, and the International Agency for Research on Cancer has classified shift work with circadian disruption as probably carcinogenic since 2007. [26] A resident who cites that at a hearing is citing real science. The question this post asks is what population that science describes, and the answer is night shift workers under overhead lighting and whole metropolitan areas measured by satellite, not a household 500 feet from a full-cutoff fixture.
Every side of the professional dispute over LED lighting, the American Medical Association and the Illuminating Engineering Society included, treats dose as decisive. [27][27a] This post rates three light-and-health claims against that standard and ends with the gap that is real: there is no federal standard for residential light exposure from adjacent industry and no established safe threshold, which is a reason to specify the fixtures, not a finding of harm.
How the ratings work. Each complaint below is stated the way it usually arrives at a hearing and rated on the scale the full article uses. Systemic: documented at compliant facilities across multiple geographies. Regional: real, but only under specific geographic or operational conditions. Isolated: documented at one or few facilities due to misconduct or atypical design. Exaggerated: the concern is real but the figures are permit ceilings or worst cases, not operating norms. Selective: a legitimate concern applied only to data centers, not to comparable land uses. Misattributed: the harm is real but the source, geography, or cause is wrong. Contested: a plausible mechanism exists but causal documentation at compliant facilities does not. Fabricated: no credible evidentiary basis exists. Where I say I found no record of something, that means a search of public sources through October 2026, not paid databases or records requests.
Light Pollution: Human Health
The mechanism is established physiology. Artificial light at night suppresses melatonin and disrupts circadian rhythm. The International Agency for Research on Cancer classified shift work involving circadian disruption as probably carcinogenic to humans (Group 2A) in 2007, confirmed in 2010 and 2020. [26] The American Medical Association’s 2016 policy on high-intensity LED street lighting found brighter residential nighttime lighting associated with reduced sleep, impaired daytime functioning, and obesity. [27] Epidemiological reviews find associations between outdoor light at night and breast cancer, type 2 diabetes, cardiovascular disease, and depression in large cohorts. [28] The claims built on that mechanism are what get tiered.
Claim: The health studies show what living near a lit data center does to you. Tier: Exaggerated. Occupational and regional exposure applied to a single facility.
The literature draws on two populations: night shift workers under high-intensity light for long hours, and whole metropolitan populations correlated with satellite-measured light across regions. Neither describes a resident at a setback from one facility. Direct light falls off roughly with the square of distance, though skyglow and reflected light do not. The AMA grounds its concern in intensity, spectrum, duration, and timing, and the Illuminating Engineering Society, which disputes the AMA’s use of color temperature as a proxy, argues that the quantity of light reaching the eye and the duration matter at least as much. [27][27a] Every side of that professional dispute treats dose as decisive. A full-cutoff fixture at a 500-foot setback is not a night shift under overhead lighting.
Claim: Data center lighting is a health risk other lit buildings aren’t. Tier: Selective.
A three-shift warehouse lights comparable or greater exterior acreage, and the mechanism applies identically. In the opposition material I have reviewed, the objection does not.
Claim: This facility’s lights will cause cancer in its neighbors. Tier: Contested.
The population studies measure aggregate light across neighborhoods, not one facility’s contribution to one bedroom, and an NCI epidemiologist writing in the British Journal of Cancer has noted that mixed findings are hard to interpret because individual exposure assessment is unresolved. [28a] I found no peer-reviewed study that measured health outcomes attributable to light from a single industrial facility. There is also no federal standard for residential light exposure from adjacent industry and no established safe threshold. Those are real gaps. Neither establishes harm at any specific facility.
What to ask for. The same specification as the wildlife post, because the fix is the same: full-cutoff fixtures, Dark Sky-compliant specifications, motion activation on non-security perimeters, and a photometric plan with each building permit that shows the light level at the nearest residential property line and bedroom-window height. [11x] That last number is the one the health literature cannot supply for a single facility and the one a neighbor is actually asking about. If a council wants to go further, a measured light-at-night baseline at the nearest homes, taken with the acoustic baseline, costs little and gives any later complaint a comparison.
What the record does not show. I found no peer-reviewed study that measured health outcomes attributable to light from a single industrial facility, and an NCI epidemiologist has written that individual exposure assessment in this literature is unresolved. [28a] Those are gaps, not clearances. Neither establishes harm at any specific facility, and neither should be cited as if it did.
This is part 11 of 13 in Thirteen Records, a series that takes the long article Data Centers Don’t Have an Environmental Record. They Have Thirteen of Them. one topic at a time. Previous: light pollution and wildlife. Next: chemical hazards, from PFAS foam to dielectric fluid to the battery building.
Cover photo: Almanta / Wikimedia Commons, CC BY-SA 4.0
Citations
[11x] United City of Yorkville, Ordinance No. 2025-77, approving the Planned Unit Development Agreement for Project Cardinal, passed November 10, 2025 (7-0), signed by the mayor November 13, 2025, published November 14, 2025; city-posted executed copy, mayor’s signature and clerk’s attestation dated November 13, 2025, Pioneer Development signature and date lines blank. Section 2.1: vesting applies “Upon commencement of the Project within three (3) years of the Effective Date.” Section 2.2: “Section 10-4-10 of the UDO is reserved for additional regulations applicable to Energy Industrial Uses. No new or amended standards, code provisions, or special regulations for Energy Industrial Uses shall apply to the Subject Property during the twenty (20) year vested term from the Effective Date of this Agreement, unless Developer agrees in writing or to the extent required by state or federal law.” No reference to Ordinance 2025-53. Section 2.14: “seventy-eight (78) feet, inclusive of any rooftop mechanical equipment or appurtenances.” Section 3.5: water obligations “addressed exclusively in the Utility Agreement.” https://www.yorkville.il.us/DocumentCenter/View/13587/Ordinance-2025-77—record?bidId= (archived: https://web.archive.org/web/20261025151237/https://www.yorkville.il.us/DocumentCenter/View/13587/Ordinance-2025-77—record?bidId=). Annexation agreement, Ordinance No. 2025-78: https://www.yorkville.il.us/DocumentCenter/View/13588/Ordinance-2025-78—record?bidId= (archived: https://web.archive.org/web/20261025151421/https://www.yorkville.il.us/DocumentCenter/View/13588/Ordinance-2025-78—record?bidId=). Packet version: City Council Packet, November 10, 2025 (ArchiveCenter Item 6499), Planned Unit Development Agreement between the United City of Yorkville and Pioneer Development, LLC (Project Cardinal), packet pp. 272 to 290. Section 2.1: entitlements “fully vested and protected from amendments and changes to City ordinances, codes, or regulations for a period of twenty (20) years from the Effective Date.” Section 2.2: “No new or amended standards, code provisions, or special regulations for Energy Industrial Uses shall apply to the Subject Property during the twenty (20) year vested term from the Effective Date of this Agreement, unless Developer agrees in writing or to the extent required by state or federal law.” Section 2.3: approximately ten-year build-out; Phasing Plan “advisory only and non-binding.” Section 2.4: “All data center buildings shall be at least five hundred feet (500′) from the nearest residential or commercial structure outside the boundaries of the Subject Property,” measured “from existing, occupied, residential or commercial buildings as of the date of PUD approval.” Section 2.10: 100-foot Transition Zone Type D buffer with a 12-foot berm facing residential properties and 8 feet elsewhere; “No additional berms or landscape requirements shall be imposed unless Developer agrees in writing.” Section 2.11: “the most appropriate location for Mechanical Equipment is on the rooftops; therefore, whenever practical, mechanical equipment shall be placed on the rooftops”; project subject to the City Noise Ordinance “as it existed when the PUD application was approved by the City Council.” Section 2.14: 78-foot maximum height including rooftop equipment. Section 2.17: “all primary power used for the data center campus on the Subject Property will be delivered from the Commonwealth Edison power grid” unless the City Council approves otherwise. Section 3.4: continuous noise monitoring devices at the onset of each construction phase, a preliminary report within 60 days after each building is operational, devices maintained for the life of the project. Section 3.11: operational testing of generators “during the hours of 11:00 a.m. to 5:00 p.m., Monday through Friday, and not on any Holidays.” https://www.yorkville.il.us/ArchiveCenter/ViewFile/Item/6499 (archived: https://web.archive.org/web/20261025154939/https://www.yorkville.il.us/ArchiveCenter/ViewFile/Item/6499)
[26] International Agency for Research on Cancer, IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 98: Painting, Firefighting, and Shiftwork. Lyon: IARC, 2010. Classification of shift work involving circadian disruption as Group 2A (probably carcinogenic to humans). Reaffirmed in Volume 124 (Night Shift Work), 2020. https://publications.iarc.who.int/Book-And-Report-Series/Iarc-Monographs-On-The-Identification-Of-Carcinogenic-Hazards-To-Humans/Night-Shift-Work-2020 (archived: https://web.archive.org/web/20261017154102/https://publications.iarc.who.int/Book-And-Report-Series/Iarc-Monographs-On-The-Identification-Of-Carcinogenic-Hazards-To-Humans/Night-Shift-Work-2020)
[27] American Medical Association Council on Science and Public Health, “Human and Environmental Effects of Light Emitting Diode (LED) Community Lighting,” CSAPH Report 2-A-16, adopted June 2016 (AMA Policy H-135.927). https://www.ama-assn.org/sites/ama-assn.org/files/corp/media-browser/public/about-ama/councils/Council%20Reports/council-on-science-public-health/a16-csaph2.pdf (archived: https://web.archive.org/web/20260909024644/https://www.ama-assn.org/sites/ama-assn.org/files/corp/media-browser/public/about-ama/councils/Council%20Reports/council-on-science-public-health/a16-csaph2.pdf)
[27a] Illuminating Engineering Society, “PS-09-17: IES Board Position on AMA CSAPH Report 2-A-16, Human and Environmental Effects of Light Emitting Diode (LED) Community Lighting.” IES formally disagreed with the AMA’s use of correlated color temperature (CCT) as a proxy for circadian health impact, arguing that quantity of light at the retina and duration of exposure are established, at least equally important inputs. https://ies.org/advocacy/ps-09-17/ (archived: https://web.archive.org/web/20261010004135/https://ies.org/advocacy/ps-09-17/) Readable report of the position: John Wallace, Laser Focus World, “The Illuminating Engineering Society disagrees with AMA policy statement on spectral content of LED outdoor lighting,” August 2, 2017 (IES: CCT “is inadequate for the purpose of evaluating possible health outcomes”; key factors are “the quantity of light at the retina of the eye and the duration of exposure”). https://www.laserfocusworld.com/articles/2017/08/the-illuminating-engineering-society-disagrees-with-ama-policy-statement-on-spectral-content-of-led-outdoor-lighting.html (archived: https://web.archive.org/web/20261025162433/https://www.laserfocusworld.com/articles/2017/08/the-illuminating-engineering-society-disagrees-with-ama-policy-statement-on-spectral-content-of-led-outdoor-lighting.html)
[28] Bozejko, M., Tarski, I., and Malodobra-Mazur, M., “Outdoor artificial light at night and human health: A review of epidemiological studies,” Environmental Research, Vol. 218, Article 115049, 2023. https://doi.org/10.1016/j.envres.2022.115049 (archived: https://web.archive.org/web/20240415131632/https://www.sciencedirect.com/science/article/abs/pii/S0013935122023763)
[28a] Jones, R.R., “Exposure to artificial light at night and risk of cancer: where do we go from here?” British Journal of Cancer, Vol. 124, pp. 1-2, January 2021 (National Cancer Institute, NIH). https://doi.org/10.1038/s41416-020-01231-7 (archived: https://web.archive.org/web/20231009234814/https://www.nature.com/articles/s41416-020-01231-7)