If you live in or visit California, you may have noticed that nearly every building has a sign that reads, “Warning: This area contains a chemical known to the State of California to cause cancer.” These warning signs are the product of California’s Safe Drinking Water and Toxic Environment Act of 1986, better known as Proposition 65 or Prop 65.     On September 2nd, 2016, the California Office of Environmental Health Hazard Assessment (OEHHA) issued amendments to Proposition 65 (California Health and Safety Code §25600 – 25607.9), which effectively overhauled the requirements for Clear and Reasonable Warnings. Due to these amendments, these over-familiar signs and labels will need to be updated or replaced to include more information than previously required. The new Clear and Reasonable Warning requirements became effective on August 30, 2018. BACKGROUND     In 1986, California voters approved Proposition 65 in response to growing concern about exposure to toxic chemicals. Proposition 65 requires the state to publish and maintain a list of chemicals known to cause cancer or reproductive harm. In addition, Prop 65 requires businesses with 10 or more employees to notify the public about potential exposure to listed chemicals through products they purchase, at their homes or workplaces, or through environmental release. This notification process is codified in Sections 25600 through 25607 of Title 27 of the California Code of Regulations (CCR) and is titled “Clear and Reasonable Warnings.” WHAT’S CHANGED? Under the old regulation, Proposition 65 warnings were required to state that a product, area, or business may expose Californians to chemicals known to the state to cause cancer or reproductive harm. Under the amended regulation, the warning must include the name of one or more chemicals that the public may be exposed to and the source of the exposure. In addition, the address for a Prop 65 informational website must be included in The warning. This requires more extensive knowledge and testing of products or exposure areas, and additional attention to detail when preparing and issuing signs and notices. A comparison of the old versus new warnings is provided in Table 1. Table 1 OLD WARNINGThis area contains a chemical knownto the State of California to causecancer. NEW WARNINGEntering this area can expose youto chemicals known to the State ofCalifornia to cause cancer, including[name of one or more chemicals],from [name of one or more sourcesof exposure]. For more informationgo to www.P65Warnings.ca.gov.     The new regulations have separate warning requirements for consumer products, food products and environmental exposure. In addition, the new Clear and Reasonable Warning Regulations  guidelines for common exposure including but not limited to diesel engine exhaust, gasoline service stations, hotels and designated smoking areas. WHY IS IT IMPORTANT?     The primary goal of the revised Clear and Reasonable Warning requirements is to provide the public with additional details on exposure from consumer products, food products and areas with environmental exposure. The addition of the specific chemical and source of the exposure provides a concise, useful warning with information on how to reduce exposure to toxic chemicals. The best example of this is the specific warning for environmental exposure at gasoline service stations:     "Breathing the air in this area or skin contact with petroleum products can expose you to chemicals including benzene, motor vehicle exhaust and carbon monoxide, which are known to the State of California to cause cancer and birth defects or other reproductive harm. Do not stay in this area longer than necessary. For more information go to www.P65Warnings.ca.gov/service-station.”     This warning provides the public with clear information on the potential hazards, as well as actions they can take to minimize exposure. The previous warnings did not inform the public on the specific hazards of service stations and provided no advice on mitigating or minimizing the hazards. In this scenario, the revised requirements achieved the goal to provide a clearer, more useful warning.     For consumer products, 27 CCR §25603(b) allows for abbreviated on product warnings where disclosure of the listed chemicals contained within the product is not required. The on-product warning must include the required warning symbol (a black exclamation mark in yellow equilateral triangle), plus one of the following statements: Warning: Cancer—www.P65Warnings.ca.govWarning: Reproductive Harm—www.P65Warnings.ca.govWarning: Cancer and ReproductiveHarm—www.P65Warnings.ca.gov     The abbreviated consumer product warnings strike a balance between providing consumers with necessary exposure information and minimizing the amount of space required to convey. Allowing the abbreviated warnings frees up valuable space on labels that manufacturers and distributors need to describe and advertise their products. WHAT ARE THE PROBLEMS?        The revised warning requirements provide clear guidelines for simple exposures to one chemical or one area. However, the requirements pose confusion for complex facilities with multiple processes and/or areas that may result in exposure to Prop 65 chemicals. For environmental and occupational exposures at indoor or well-defined outdoor areas, warnings must be posted at all entrances, and the new requirements state that the warnings must include “one or more” chemicals and “one or more” sources of exposure. This leaves the question: Do these warnings need to include every chemical and every source of exposure or at least one chemical and at least one source?     The common interpretation is that “one or more” means just that, one or more, not all. This interpretation would result in warnings that omit potentially hazardous exposures. For example, if a facility had a surface coating operation and a soldering operating in the same large room, both of these operations have the potential to expose employees and visitors to Prop 65 chemicals. The painting operation may result in the release of solvents such as toluene, and the soldering operation may result in the release of toxic metals, such as lead. The “at least one” approach would lead to a warning sign that reads: “WARNING: Entering this area can expose you to chemicals known to the State of California to cause cancer and birth defects or other reproductive harm, including lead, from emissions associated with soldering operations. For more information go to www.P65Warnings.ca.gov.”     This warning omits the potential exposure to toluene from painting operations. Under this scenario, have workers that are stationed near the surface coating operation been adequately warned? Unfortunately, this question will most likely be answered in a future lawsuit, and facilities will have to wait and see what happens. The alternative is that warnings require every chemical and every source of exposure. For some facilities—refineries for example—this would be impossible, and the warnings would be the size of a multi-car garage. WHAT’S THE BOTTOM LINE?     One of the goals of the recent amendments is to reduce lawsuits related to Proposition 65. However, the final rule may have the opposite effect due to the complexity of the new warning requirements. Manufacturers and distributors of consumer products must update or redesign their labels for products sold in California, and retailers need to work with their distributors to acquire adequate information and signage to display the proper warnings. Facility owners and managers are required to determine exactly which listed chemicals are present in their living and working spaces and develop new warning signs that include those specific chemicals. Managers of industrial facilities required to send out quarterly notices need to update their public notice content and delivery method to meet the new requirements. Additional analysis or modeling may be necessary to develop the map that is required with the notice.     Overall, the new amendments have made the warning requirements more specific, which may provide the public with more information. However, they have increased the burden on entities required to provide the warnings and opened the door for a new round of lawsuits due to the unanswered questions regarding interpretation of the new requirements.  Chris Waller, C.P.P., is team manager, EHS & air, at Alta Environmental (www.altaenviron.com), an environmental engineering and consulting firm.