Toxicology Corner: Artificial Dyes & Coal Tar

I’ve always had a crazy sweet tooth. You might remember those tubes of disgustingly sweet and insanely colored goo that was supposed to be like fake toothpaste? I ate that. Yup, I was that kid. I didn’t think about what was in my candy, I only cared if it was sweet and delicious. So almost all of that candy was brightly colored with artificial dyes.

These dyes, now ubiquitous in our consumer products, are petrochemicals. They are made from coal tar, the thick brownish liquid that is a by-product of processing coal.

So, what are coal tar dyes exactly?

Coal tar color additives are dyes made by combining a number of chemicals produced from distilling bituminous coal; these include compounds like toluene, xylene, or benzene. Nowadays, they’re also made from petroleum, although still referred to as coal tar dyes.

History fact: Mauve was the first color created from coal tar, although not purposefully, just an accidental discovery by a British chemist in 1856.

Widespread use of coal tar dyes started in the early 1900s, and like other chemicals, there was no requirement for testing or safety evaluation before they were released onto the market. This changed after Halloween in 1950, when children all over the US became sick from ingesting candy with Orange No. 1 dye. Further study revealed the dye to be toxic – causing diarrhea, abdominal pain, weight loss, even death (in animal studies). Testing of other coal tar dyes produced similar results, prompting the US government to start regulating and restricting the use of these food dyes. The set of coal tar dyes we use today emerged as those considered safe by the FDA after thorough testing in the early 1960s.

What are the health risks of dyes and coal tar?

Despite approval from the FDA, there has been intermittent concern since the 1970s over the actual safety of any coal tar dyes (and coal tar itself), primarily in terms of links to childhood behavioral problems and cancer.

In the early 1970s, a doctor from California proposed the idea that artificial dyes and flavors were causing or exacerbating hyperactivity in children (ADHD), although he didn’t have much evidence to support this theory. The possible link was studied, but any connection was deemed statistically insignificant. However, in the early 2000s, two studies confirmed a small, but significant influence of artificial dye on behavior in British children. The EU decided this was enough to warrant a warning label on foods, but the FDA dismissed the idea of a warning due to a lack of overwhelming evidence. However, many consumers, and parents especially, are choosing products that are free of artificial dyes. Over the years, we have gathered anecdotal evidence of behavioral changes in children from consuming artificial dyes. So at what point do these personal accounts become solid evidence, not just anecdotes?

Scientists have discovered that Blue No. 1 is capable of crossing the blood-brain barrier, but there is no research on the health impacts of this occurrence. This barrier is supposed to protect us from toxins, so if some petrochemicals can cross it, how might that affect our brains and biological functions?

Coal tar itself is a known carcinogen and can be contaminated with heavy metals and other toxic chemicals; the EWG gives it a score of 10, with ample data for support. The EWG scale is 0-10 with 10 being extremely hazardous. It’s also a skin allergen and irritant. Ironically, coal tar is used in many treatments for eczema and psoriasis; it does not cure these conditions, it merely temporarily relieves symptoms and masks the underlying problem.

There is insufficient data to say whether topically applied coal tar and its dyes are linked to cancer, but this is where the precautionary principle comes into play. Given what we know about coal tar and petrochemicals, it just seems unsafe to use them at all.

On a personal note, I used a prescription eczema cream when I was in my late teens/early 20s and my symptoms just spread and worsened over the years. As I learned about toxic chemicals, I realized my medicated cream contained petrochemicals linked to skin irritation. I stopped using it and eliminated all skin products with petrochemicals – it was a world of difference. My eczema subsided and quickly vanished. I haven’t had any flare ups of my eczema in about 7 years.

How to spot coal tar and dyes

Coal tar and its distillates have many names. Look for any of these on ingredient labels:

Coal tar solution, tar, coal, carbo-cort, coal tar solution, coal tar solution USP, crude coal tar, estar, impervotar, KC 261, lavatar, picis carbonis, naphtha, high solvent naphtha, naphtha distillate, benzin B70, petroleum benzin.

Color additives are usually towards the bottom of an ingredient list. Look for these:

FD&C: Blue No. 1, Blue No. 2, Green No. 3, Yellow No. 5, Yellow No. 6, Red No. 3 and Red No. 40. Orange B and Citrus Red No. 2 (allowed, but with restricted use).

D&C: Black No. 2, Black No. 3, Green No. 5, Orange No. 5, Red No. 6, Red No. 7, Red No. 21, Red No. 22, Red No. 27, Red No. 28, Red No. 30, Red No. 33, Red No. 36, and Yellow No. 10.

Lakes: These dyes are made from FD&C colors and then prepared using metal salts as binders to prevent color bleeding.

Additionally, P-phenylenediamine is a specific coal tar dye that is approved for use in hair dyes, although a warning label that it can irritate the skin must accompany it. There is strong epidemiological evidence linking this chemical to tumor growth and cancer.

Note on ingredient labels: Color additives may also include a CI (Color Index) number, which is the European Union method of identification. This applies to all color additives, including non-petrochemicals like titanium dioxide and Annatto.

Status on this issue?

Under the Federal Food, Drug, and Cosmetic Act (FD&C Act), the FDA does regulate color additives in food and cosmetic products. All food-coloring additives must be labeled, with the exception of dyes that come from vegetables, minerals, or animals. The ambiguous “natural color” is most likely not some crafty way of hiding toxic chemicals.

FD&C dyes are approved for food, whereas D&C colors are allowed in “non-food” items, like personal care products or medicine/drugs. This situation is an example of how ridiculously weak citizen health protection is – we still absorb chemicals through our skin that can cause bodily harm and why would an ingredient be unsafe in food, yet acceptable for medicine that’s ingested?

If you want to learn more about the specific dyes and their usage, see the FDA’s Additive Status List.

So, I do have some good news! A handful of companies are starting to remove artificial dyes from their products regardless of laws or regulations. They’re switching to natural sources of dyes, including turmeric, beets, paprika, and annatto.

Companies switching include Nestlé USA, General Mills, Kraft, Frito-Lay, Kellogg’s, Campbell’s, and Mondelez International (Oreos/Sour Patch Kids). Black Forest Gummies are another candy that does not contain artificial dye. The list of foods available without toxic dyes is certainly growing! Just keep checking those labels to find safe products, support or encourage companies that are eliminating toxic dyes, and keep demanding safer ingredients from all companies!



Causality versus Correlation: Why don’t we just outright say chemicals cause illness?

In the realm of toxic-free and safer consumer products, you might have noticed that when we refer to chemical health risks we tend to use phrases like, “may increase risk of…” or “connected to” rather than simply saying a chemical “causes” an illness.

Why is this? There are two main reasons, which are tightly connected:

1. We don’t want to overstate claims of causality and lose everyone

One problem the non-toxic movement struggles with is keeping people engaged in forward momentum to change things without scaring everyone away with alarmist or extremist sounding claims. To claim that a chemical causes disease without 100% proof or sufficient evidence, we’re embellishing the truth, simplifying the facts, and we risk discrediting everything completely. While there is strong evidence that there are connections between illnesses and toxic chemicals, toxicologists and ecologists working on these issues work hard to present the information truthfully and in keeping with scientific data.

2. We cannot guarantee causality 100% with the majority of chemicals we suspect to be toxic

Why is this? There are a few reasons, but they come down to a lack of clear, concrete data on the isolated and synergisticˆ impacts of chemicals.

Temporal and spatial disparities:

This is a fancy way of saying that time and space put distance between exposure and illness, creating complexities of pinpointing causes. For example, PCBs are found in areas incredibly far away from anywhere they were actually used. Winds and water currents have moved them around the entire globe, and this is true with other chemicals as well. Additionally, exposure to a chemical in the womb may be the cause of developing a cancer later in life. Toxic chemicals move around so unrestricted, it’s hard to keep track of when and where exposure may have happened that resulted in an illness. On a population scale, some of the effects of chronic exposure to toxic chemicals may not be felt for a generation or two. Or different impacts will be felt generations later that might be hard to trace back to the original source. Today, men are facing decreased sperm counts, and many attribute this to generations of exposure to EDCsˆ.

Our entire world is contaminated:

Scientists are finding it difficult to conduct studies properly due to contamination of our environment, often times eliminating the availability for a control. One example of this situation is from the late 1980s, when two scientists were attempting to conduct studies on breast cancer cell growth in the presence of estrogen. They found all of their cell tissues contaminated with a mystery source of estrogen, which was throwing off their tightly controlled cell experiments. Research halted. At a total loss for answers, they even suspected sabotage at one point. Finally, they tracked down the contamination source to the plastic tubes used to store blood. Chemicals from the tubes, which they’d long assumed to be inert, were leaching into the blood and contaminating it with estrogen. On a broader scale, it’s difficult to assess human health impacts from exposure when all of us are polluted to some degree.

There was little testing conducted to begin with:

Thousands of chemicals were introduced to consumer markets without proper testing of each chemical, let alone testing for synergistic impacts. With some chemicals, it’s hard to say which one causes a problem, or if health risks only appear when chemicals are used in certain combinations. We don’t really know because no one bothered to check that carefully.

The impacts of toxic chemicals are often subtle, rather than direct and obvious:

With some toxins, illness caused is simple to identify because it happens quickly and directly. This is the case with extreme exposure to radiation, or acute poisoning from certain heavy metals. Many pesticides used during the 1950s/1960s had clear and often immediate health consequences for humans and the environment. However, many toxic chemicals on the market today change DNA and slowly impair bodily functions, or cause unseen damage to fetuses. Considering how many chemicals we are exposed to, sometimes it can be hard to identify which one might be the culprit.


The current evidence against toxic chemicals remains in the area of correlation. One exception is the case of the DES Daughters. DES (diethylstilbestrol), banned in 1971, was a synthetic estrogen drug given to women during the 1940s and 1950s to prevent miscarriages. The effects of DES were realized after doctors in Boston saw a startling increase in young women with an extremely rare form of vaginal cancer. The mothers of these young women had all taken DES while pregnant. Most of the health impacts of DES were not present at birth, but began to appear as the women reached puberty, childbearing age, and mid-life. DES Daughters are twice as likely to develop breast cancer, and face high rates of other ovarian and vaginal cancers, infertility, and reproductive organ deformities.

Possibly, if we can pinpoint extreme exposure cases or track and correlate specific habits and behaviors with chemical exposure, we may find stronger links between health risks and specific chemicals.


Endocrine Disrupting Compounds and Cancer in Wildlife and Humans (research paper written by me!)
Our Stolen Future by Theo Colborn, Dianne Dumanoski, and John Peterson Myers
Not Just a Pretty Face by Stacy Malkan

ˆ Denotes a term that is defined/explained under the terms/concepts/glossary page of blog. Symbol found following the word the first time it’s used in a post.