Broad Spectrum Is Not a Given: Getting UVA Protection Right
SPF mostly measures protection against the rays that cause sunburn. Dr Leslie Laquieze explains why UVA protection must be measured separately, what changed in the international UVA method in 2026, and how to handle tinted products.
By Dr Leslie Laquieze, PharmD, MSc, PhD, MBA, Expert Member, Australian Sunscreen Council
A high SPF does not prove a sunscreen protects well against UVA. The two are related, but they are distinct domains, and they must be evidenced separately.
Why UVA matters
The Therapeutic Goods Administration explains on its page Sunscreen SPF testing – information for consumers that “while the SPF number on a sunscreen mostly tells you how well it protects against UVB, broad spectrum testing ensures the product also shields you from UVA rays—which could cause long-term skin damage and can lead to skin cancer.”
The TGA’s Australian Regulatory Guidelines for Sunscreens define a broad-spectrum product as “a sunscreen product which has been shown, using the in vitro test method defined in the Australian Sunscreen Standard to provide protection from the sun’s terrestrial UVA and UVB rays.”
UVA protection is critically important for skin cancer prevention. In a landmark Sydney study published in the Proceedings of the National Academy of Sciences, Agar and colleagues (2004) examined human skin squamous cell carcinomas and solar keratoses and found UVA fingerprint mutations “mostly in the basal germinative layer,” in contrast to “a predominantly suprabasal localization of UVB fingerprint mutations.” The authors concluded that “longer-wavelength UVR is an important carcinogen in the stem cell compartment of the skin” and that “the importance of protecting the population not just from UVB but also from UVA irradiation has profound implications on public health worldwide.”
Formulators may use broad-spectrum filters such as zinc oxide and bemotrizinol as part of a UVA strategy, but performance remains dependent on the complete formulation and film. Australians have long had access to bemotrizinol; the United States added it to the OTC sunscreen monograph in June 2026 under FDA Final Order OTC000039.
Broad spectrum also matters for indications. The TGA’s March 2026 consultation paper lists the indications currently permitted for broad-spectrum sunscreens with SPF 30 or higher, including “May assist in preventing some skin cancers” and “May reduce the risk of some skin cancers.” A broad-spectrum failure therefore undermines not only a label word, but the most important health claims a sunscreen can make.
The method: ISO 24443
The ISO abstract for ISO 24443:2021 states that it “specifies an in vitro procedure to characterize the UVA protection of sunscreen products” and “is not applicable to powder products such as pressed powder and loose powder products.” The TGA’s 2024 paper on the proposed adoption of AS/NZS 2604:2021 explains that the 2021 edition added “a method for calculation of critical wavelength,” new reference sunscreens for higher-performing broad-spectrum products, and “changes to account for photo-stability of test products by exposing them to specific measured doses of ultraviolet (UV) radiation prior to testing.”
A 2026 amendment laboratories must assess
Amendment 1 to ISO 24443:2021 was published in February 2026; the official ISO entry for ISO 24443:2021/Amd 1:2026 confirms its published status. The amendment includes an annex on robotic spreading, and a corrected French version is dated September 2026.
Laboratories should identify the exact edition and amendment used for every report and complete an impact assessment before changing standard operating procedures. Sponsors should ask which version was applied and whether the change affects comparability with earlier results.
Practical rules for UVA evidence
· Use the Australian criterion. Assess broad-spectrum compliance against the criterion in the applicable edition of AS/NZS 2604. Do not assume that a European UVA logo or a United States broad-spectrum result is interchangeable.
· Do not infer UVA from SPF. ISO 24443 relies on a reliable static SPF value for scaling, so a weak SPF result can also compromise the UVA calculation.
· Characterise tinted products shade by shade. Pigments and iron oxides change how a film absorbs and scatters light, so film uniformity, transmission and long-wave UVA performance should be assessed. Any decision to bridge results between shades should be justified with data.
· Retest after relevant change. Review UVA performance after any change that may affect concentration, dispersion, photostability, rheology, volatility or optical properties.
The regulator can test this
Unlike in-vivo SPF, broad-spectrum performance is measured in the laboratory, and the TGA can test it directly. Its consumer information page states that while it does not conduct human or animal testing, “we do conduct other testing of sunscreen products, such as laboratory broad spectrum performance testing as per the Australian Standard (AS/NZS 2604).” The TGA’s sunscreens hub also states that it monitors therapeutic sunscreens “through both compliance reviews and laboratory testing of things like active ingredient amounts and broad spectrum activity.” Sponsors should assume their broad-spectrum claim can be checked at any time.
Sources
· Therapeutic Goods Administration, “Sunscreen SPF testing – information for consumers”: https://www.tga.gov.au/resources/explore-topic/sunscreens/sunscreen-spf-testing-information-consumers
· Agar NS et al., “The basal layer in human squamous tumors harbors more UVA than UVB fingerprint mutations: A role for UVA in human skin carcinogenesis”, PNAS, 2004;101(14):4954–4959: https://www.pnas.org/doi/10.1073/pnas.0401141101
· US Food and Drug Administration, “Questions and Answers: FDA’s regulatory actions on over-the-counter sunscreen”, including Final Order OTC000039 of 10 June 2026: https://www.fda.gov/drugs/understanding-over-counter-medicines/questions-and-answers-fdas-regulatory-actions-over-counter-sunscreen
· Therapeutic Goods Administration, “Australian Regulatory Guidelines for Sunscreens”, Version 3.0, May 2023: https://www.tga.gov.au/sites/default/files/australian-regulatory-guidelines-for-sunscreens.pdf
· Therapeutic Goods Administration, “Proposed adoption of AS/NZS 2604:2021”, April 2024: https://www.tga.gov.au/sites/default/files/2024-04/proposed-adoption-the-australian-new-zealand-sunscreen-standard-as-nzs-26042021.pdf
· International Organization for Standardization, ISO 24443:2021: https://www.iso.org/standard/75059.html
· ISO 24443:2021/Amd 1:2026, catalogue entry: https://www.iso.org/standard/91166.html
· Therapeutic Goods Administration, consultation paper, March 2026: https://consultations.tga.gov.au/tga/improvements-to-regulation-of-sunscreens-in-aus/user_uploads/final---consultation---seeking-feedback-on-improvements-to-the-regulation-of-sunscreens-in-australia---v1-march-2026-2.pdf
· Therapeutic Goods Administration, “Sunscreens” hub: https://www.tga.gov.au/resources/explore-topic/sunscreens
About the Author
Dr Leslie Laquieze (PharmD, MSc, PhD, MBA) is a pharmacist-scientist and international expert in sunscreen testing, photoprotection, skin pharmacology and dermocosmetic claim substantiation. An expert member of the Australian Sunscreen Council, she has led Kosmoscience Europe since 2018, supporting the evaluation, substantiation and regulatory positioning of cosmetic and dermatological products across international markets.
This article reflects the opinion of Dr Leslie Laquieze. Readers are recommended to seek expert legal advice on all issues discussed.
