A proposed bill in California is looking to ban the manufacturing, sale, or distribution of foods containing red dye No. 3, titanium dioxide, potassium bromate, brominated vegetable oil, or propylparaben — chemicals that appear in popular candies like Skittles and Nerds, the Washington Post  reports.

What you need to know about these 5 chemicals

1. Titanium dioxide

Titanium dioxide is a white food colorant commonly used in candies and processed foods to give the food a smooth texture, the Post  reports. It is commonly used in Skittles and Nerds.

According to the  Environmental Working Group, "The pigment can brighten other colors, making the food more vibrant and appealing, but the additive has no nutritional benefit."

The chemical was banned by the  European Union  (EU) last year after the EU found it could "no longer be considered safe when used as a food additive."

The  European Food Safety Authority  said it couldn't exclude the potential that titanium dioxide could lead to carcinogenic effects, and added that its assessment of the chemical showed that "after oral ingestion, the absorption of titanium dioxide particles is low, however they can accumulate in the body."

In a 2017 review from Europe published in  Nature, researchers said titanium dioxide could accumulate in a person's body, including in their bloodstream, kidney, liver, and spleen.

FDA  says the chemical can be safely used for coloring foods, provided it doesn't exceed 1% of the weight by food.

Callie Noakes, a spokesperson for  Mars, which makes Skittles, said the company "always follow[s] local regulatory rules, and all of our treats and snacks are made to the very highest quality and adhere to the strictest safety standards."

When asked about the difference between Skittles in the United States and Europe, Noakes said the "recipes vary slightly across the globe" and that "this is largely to accommodate manufacturing capabilities, local availability of raw material, or the different taste preferences of people."

2. Red dye No. 3

According to  Just Born, the production company of Hot Tamales and Peeps marshmallows — both of which use red dye No. 3 — the food coloring provides "a distinct and recognizable color" and that certified food colors are "highly regulated for purity and each batch produced must meet exacting standards and be approved by the FDA before they can be sold by the manufacturer."

In the EU, red dye No. 3 is only authorized for use in certain cocktail cherries or candied cherries, the  Post   reports.

FDA banned the use of red dye No. 3 in cosmetics and externally applied drugs in 1990, based on an analysis of unpublished research on animals that suggested the dye was linked to thyroid cancer. However, FDA still allows the use of the dye in foods, dietary supplements, and ingested drugs.

Currently, there's no evidence that red dye No. 3 or any artificial food colorings can cause cancer in humans, the  Post  reports. However, other  studies  have linked the food coloring and other artificial dyes to hyperactivity and other behavioral problems in children.

3. Potassium bromate

Potassium bromate is commonly found in baked goods and has been banned in Brazil, Canada, India, and throughout Europe. Britain also banned the chemical in 1990 over concerns it was a carcinogen.

EU's chemicals agency says potassium bromate is "toxic if swallowed" and "may cause cancer," while FDA says it can "safely be used in the malting of barley" under certain conditions.

Potassium bromate was approved by FDA in the 1960s, however according to the Environmental Working Group, the chemical hasn't been reassessed since the 1970s.

4. Brominated vegetable oil

Brominated vegetable oil is sometimes used to prevent ingredients from separating and floating to the top of drinks, the  Post  reports.

It is currently banned in Europe but is still used in Sun Drop citrus soda in the United States. FDA allows the chemical to be used "in a small amount" but said it has "identified areas where additional information about possible health effects is needed."

Brominated vegetable oil has also been found to aggravate skin membranes and drinking very large quantities of it has been linked to neurological symptoms like memory loss and headaches.

5. Propylparaben

Propylparaben is a preservative used in cosmetics and in food, often found in baked goods and certain cake icing brands, the  Post   reports.

According to FDA, propylparaben is "generally recognized as safe" provided it doesn't exceed 0.1% in food. In the EU, the chemical is not approved for use as a preservative, after research suggested it had an impact on the reproductive system of male rats.

The Environmental Working Group said the chemical is "linked to disruptions in hormone signaling." However, some critics have argued research on rats from the early 2000s is outdated and that European food safety regulators should reassess propylparaben.

A  CDC  study spanning 2005 to 2006 found that propylparaben was present in the urine of most people tested, and that there is widespread exposure throughout the U.S. population. However, the researchers added that "finding a measurable amount of parabens in urine does not imply that they cause an adverse health effect."

California lawmakers look to ban food chemicals

The proposed bill in California is seeking to ban these five food chemicals, arguing they are "dangerous" and already banned in the EU and other countries.

However, State Rep. Jesse Gabriel (D-Woodland Hills) who authored the bill, noted that there's "a zero percent chance this is actually going to result in a ban of Skittles," adding that he hopes companies will adjust their recipes like they do in other countries.

In response to the bill, several food industry groups sent a letter saying, "All five of these additives have been thoroughly reviewed by the federal and state systems and many international scientific bodies and continue to be deemed safe."

The  National Confectioners Association  in a statement said that "[f]ood safety is the number one priority for U.S. confectionery companies, and we do not use any ingredients in our products that do not comply with the FDA's strictest safety standards." (Hassan et al., Washington Post, 3/23)