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.

Minefield of Chemicals: Toxic Fragrance (part 2)

How to avoid fragrance chemicals:

  • Read labels: avoid “fragrance (parfum)” without any detail
  • Look for “fragrance-free” official label
  • Avoid air fresheners and perfumed cleaning products; try natural ways to eliminate odors
  • Choose products that disclose source of fragrance: essential oil blends or botanicals
  • Find trustworthy companies with certifications that backup claims of “no synthetic fragrances”
  • Switch to green cleaning or DIY cleaning

My last fragrance article focused on perfume/cologne, but fragrance chemicals are present in many more consumer products. We are so inundated with fragrance in our society that its prevalence often goes unnoticed. Go to a store like Target or Fred Meyer (subsidiary of Kroger), walk around all the departments, and notice where you find fragranced products. Fragrance is heavily used in personal care products, but it’s also used in clothing, children’s toys, cleaning supplies, trash bags, Kleenex, and even feminine hygiene products.

The heavy use of fragrance is one of the worst problems because it makes everyday life difficult for those with sensitivities, limits consumer choices, and exposes people to toxic chemicals without their consent. The use of fragrance in public space is similar to the secondhand cigarette smoke issue. Smoking and using fragrance are not just individual lifestyle choices because they affect other people without their consent. This also pertains to company choices to use fragrance in public spaces, such as air fresheners in hotels or workspaces. Additionally, individuals should not have to work so hard to find products that are free of fragrance chemicals or are not unnecessarily scented. Even products labeled as “unscented” sometimes contain fragrance to mask the smell of other chemicals. The EPA has defined “fragrance-free” as an official term manufacturers can use to indicate that a product contains no fragrance chemicals; this is part of the Safer Choice label program.

So, what are some of the toxic chemicals used in fragrances and why should we be concerned? In my last fragrance post, I went over briefly some of the health risks associated with fragrance ingredients. Here, we’re going to examine just a few of the chemicals found in fragrance to give you a snapshot of why synthetic fragrances are so concerning. I think an important thing to keep in mind is how unregulated the fragrance industry is, so we’re not just worried about the health risks alone, it’s a combination of these ingredients being potentially toxic and having basically no safeguards to protect us.

  • Acetaldehyde: Affects kidneys, reproductive, nervous, and respiratory systems. Classified by CA Prop 65ˆ as known/suspected carcinogen. IARCˆ (International Agency for Research on Cancer) and the NTPˆ (National Toxicology Program) list it as a possible carcinogen.
  • Butylated hydroxyanisole (BHA): Possible endocrine disruption; also listed as carcinogen by CA Prop 65.
  • Butylated hydroxytoluene (BHT): Stabilizer and preservative. Eye and skin irritant and possible respiratory system irritant. Limited evidence of thyroid damage, including cancer, from BHT.
  • Dichloromethane (methylene chloride): Shown to cause mammary gland tumors and classified as possible carcinogen by IARC and NTP. Also, possible carcinogen to individuals working with it. Use is restricted by European Commissionˆ and it’s been banned by the FDA.
  • Diethyl phthalate: Fragrance solvent that’s a possible endocrine disruptor and neurotoxin; poses threat to reproductive system. Irritates eyes, skin, and respiratory system.
  • Formaldehyde: known human carcinogen. Banned in personal care products in Japan and Sweden. European Union and Canada restrict it. CA Prop 65 states in gas form, its carcinogen. Individuals working with formaldehyde are at risk of cancer and immune system impairment.
  • MEA, DEA, TEA – ethanolamine: When used in conjunction with certain preservatives, they form nitrosamines (a chemical class). The IARC and NTP consider various compounds in this chemical class as possible or known carcinogens.
  • Oxybenzone (BP-3): This UV filter is a possible EDCˆ; it might be toxic to liver cells and can accumulate in the body. European Union regulates its use in cosmetics.
  • Propyl paraben (propyl p-hydroxybenzoate): Possible endocrine disruptor (EDC). Banned by Denmark for children’s products under 3 years old. European Commission restricts its use in cosmetics.
  • Styrene: Toxic to blood cells and liver when ingested; neurotoxic when inhaled. European Commission classifies it as a “category 1” endocrine disruptor, which means there’s strong evidence that it is carcinogenic.
  • 1,4-Dioxane: This is a byproduct of making other chemicals and a common contaminant in final products. Since it’s a contaminant, it doesn’t need to be disclosed on ingredient labels. Under CA Prop 65, it’s known or suspected to cause cancer and birth defects. IARC and NTP both list it as possible carcinogen.

These substances are only a few of the thousands used in fragrance blends, but it gives you a good sense of the types of health concerns we’re dealing with. The evidence to support health risks is weak though, because most substances are not really tested. It’s difficult to make environmental and public health assessment on substances when there is insufficient data.

In addition to these chemicals, there is some evidence that certain chemical compounds found in essential oils may be harmful to our health and the environment. My next post in this fragrance series will dive deeper into that aspect.



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.

Tips for Evaluating Product Safety & Reading Ingredient Labels

Reading ingredient labels is an essential part of switching to non-toxic products. You have to be careful to not make assumptions that a product is safe based on its label claims, like “all natural” or “dermatologist recommended”. That does not necessarily guarantee a product is safe. Here are a few tips that I found to be helpful in making decisions about products:

  • Scan the bottle first. What you’re looking for:
    • Are there any certifications on the product? USDA, leaping bunny, Oregon Tilth, etc… (I’ll do a blog post on these at some point)
    • Does it tout “all natural” or something to that effect and have no apparent evidence that support this claim?
    • Face-wash specific: does it say “oil-free” – that is a bad sign
  • Scan the ingredient list. What you’re looking for:
    • How long is the ingredient list? Are ALL the active AND inactive ingredients disclosed, if applicable?
    • What are the first five ingredients?
    • Are ingredients labeled organic?
    • Do you recognize the ingredient names as plants or fruits?
  • Learn the basic toxic chemicals to avoid and what is normal to expect in different products (like a lotion is usually a mix of water and a bunch of oils; shampoo will have some kind of foaming agent or soap in it)

I have discovered, after years of looking at different ingredient lists, that there are patterns to the words that are usually the toxic ingredients. There are similarities that you can use in your initial assessment to determine if an ingredient is worth a second look. These are some of the things that catch my eye when I scan a list of ingredients:

  • Words or parts of words: e.g., Butyl, propyl, methyl, lauryl, -ic, –ene, -ate, carbomer, petrolatum, paraffin
  • Numbers:  e.g., 1,4- or -120
  • Capitalized abbreviations: e.g., PEG, EDTA
  • Numerical prefixes or parts: e.g., penta, poly, deca, abbreviations (like EDTA),
  • Artificial dyes: (colors with numbers or the word “lake”) e.g., red 40
  • Fragrance or parfum (unless from essential oils or botanicals)

This image below nicely lays out how to identify petrochemicals in your products. I got this from a Canadian company called Cocoon Apothecary.  

Remember that this is a constant process, and even I continually agonize over comparing products, determining safety of ingredients, and sometimes fail to catch that one little deal-breaking chemical in the long ingredient list of a product. My bottom line recommendation is just be patient, take a few minutes to look carefully at products, and don’t be too disheartened if you think a product is safe and then find out it probably isn’t.

Other resources:

Toxic Chemicals and the Legacy of Rachel Carson (Part 1)

…the central problem of our age has therefore become to contamination of man’s total environment with such substances of incredible potential for harm – substances that accumulate in the tissues of plants and animals and even penetrate the germ cells to shatter or alter the very material of heredity upon which the shape of the future depends.       ∼ Silent Spring, p. 18

Rachel Carson

Rachel Carson wrote these words in 1962. Silent Spring is one of the most significant publications in environmental writings, because it was the first time anyone had chronicled the human health and environmental horrors of pesticides and toxic chemicals. She was a marine biologist who dedicated her life to writing about scientific research, bridging the wide gap between social sciences and life sciences. She had the unique ability to translate facts and data into compelling and influential stories. Her ability to bring environmental issues into public conscience made her a pioneer in the field of ecology and many credit her as the spark that ignited the 1960s environmental movement.

Carson was instrumental in the banning of DDT, a toxic pesticide that is the focus of Silent Spring; this marked the beginning of a long struggle against the pollution of our environment from man-made substances.

Furthermore, we should remember that Carson was working during the 1950s and 1960s. She died in 1964 from breast cancer, which she chose to keep secret because she felt it would discredit her as a scientist. Most likely, this is true. As a female scientist, she had to work even harder to prove her worth to her colleagues and to a male-dominated Congress that she would address in 1963. Thus, she is rightfully known as one of the great women in history that made waves.

Although written over half a century ago (yeah, it sounds crazy when you frame it that way), it is frightening how relevant Silent Spring remains today. At the time of publication, chemical manufacturers were well underway in their total pollution of our ecosystems.

So, how did this start? In the early 1900s, chemists began experimenting with synthetic plastics and nylons derived from petroleum. These plastics were used in abundance in military equipment during WWII as a cheap, durable, and versatile alternative to natural materials. After the war ended, the petrochemical industry turned to the consumer market to maintain profits. DuPont’s motto of “better living through chemistry” became a motto for the 1940s and 1950s as pesticides, plastics, chemical beauty products, and miracle cleaning products became all the rage. With basically zero testing before introduction to consumer markets, no one really stopped to think about how all these new chemicals would impact humans, animals, and our environment.

Most of the damage done by environmental toxins is long lasting and slow to appear. Unlike the choking smog of London during the industrial revolution, much of our pollution creeps into our soil, our water, our very DNA, and stealthily tweaks essential biological functions for generations. It has taken massive and obvious tragedies, deaths, disfigurements, and communities ripped apart for us to take any action.

One of the most famous cases, which helped instigated the formation of the EPA’s Superfund program, took place in a small town called Love Canal. The short story is that a chemical company dumped toxic waste, covered it with dirt, sold it to the town, and disaster struck after a large rainstorm in the form of chemical burns, birth defects, mental retardation, and cancer.

This is the history upon which our fight against toxic chemicals stands. While there may be irreparable damage from persistent substances in our environment, we must remember that not all threats to our existence are transparent and immediately obvious; they are however, still urgent.

In part two of this post series, I will discuss the formation of toxic chemical regulations and current policy in regard to the oversight of the personal care industry.