Stories: The Toxic Mistake

Today, I'm going to tackle one of the most infamous urban legends, which caused countless people to panic and discard a houseplant out onto the streets! It goes something like this. There was a self-proclaimed 'expert' who investigated a case of malignant cancer that afflicted his friend. The person found that the cancer patient planted many Zanzibar gem or ZZ plant (Zamioculcas zamiifolia) in his room. He 'tested' the plant and found that it is full of cancer-causing toxins, particularly in the pollen. The plant can even release cancer-causing gases into the air we breathe. He published his results in a local Chinese newspaper, and things blew up out of control. The Chinese particularly favours the Zanzibar gem as a Feng-Shui charm, and it is often nicknamed the money plant (金钱树). However, since the cancer scare surfaced on 2015, the ZZ plant has become a public enemy even until today. This is a great example of what sensationalised social media and health hoaxes can do, but before everyone gets emotional, what does science have to say about it? After all, just like any urban legends the overwhelming 'toxicity' of the Zanzibar gem actually has its root. 

Zanzibar gem (Zamioculcas zamiifolia, Araceae)

Sensationalised report of Zanzibar gem's toxicity. Source: Local Malaysian tabloid rojaklah.com.

The Zanzibar gem plant belongs to the aroid family (Araceae), which is indeed poisonous. The Aroid family includes many other ornamental plants such as Aglaonema, Alocasia, Caladium, Colacasia, Dieffenbachia, Epipremnum, Monstera, Philodendron and Spathiphyllum, all of them harbour the same toxin called calcium oxalate. That’s actually a simple chemical salt made of calcium, oxygen and hydrogen, and it's largely insoluble in water. But what can a salt do? It can form crystals. Many aroids have special compartments in their cells to grow calcium oxalate crystals in the shape of sharp spikes or needles called raphides. We have encountered this toxin before in my story of the forbidden grape. If an animal or human eats the plant, these sharp crystals are released, and they will poke the attacker’s mouth and airway. This causes intense pain, swelling and difficulty swallowing or speaking. Instances of poisoning due to ingestion of zanzibar gem is well documented, usually in young children. They present with pain and swelling in the mouth, but the toxicity is self-limiting and resolves within a day or two given supportive care (see Figure 1). To the best of my knowledge, no one has been confirmed to die from the Zanzibar gem. However, I should remark that most people who got into accidents with Aroids are due to eye-exposure. The crystals can also poke your eyes, so clean your hands properly if you come into contact with Aroid sap! 

 

Documented cases of Zamzibar gem toxicity in humans. Ref: Gamage, G. Sri. Lanka J. Child Health. 2020, 49, 195-196.

How about ZZ plant's ability to cause cancer? Or emit harmful carbon dioxide into the air at night. Remember that cancer is a complicated disease, and there’s usually no single cause to cancer because our bodies are good at preventing cancer in the first place. To get cancer, one needs six conditions: 1.) gene mutation or activation of pre-cancer genes; 2.) cancer suppressor gene damage; 3.) cells refuse to die when their time is up; 4.) gene repair malfunction; 5.) evasion/weakening of immune system; 6.) formation of blood vessels around cancer cell. As far as I know, ZZ plant can do none of the above, at least in the lab. Cancer is a side effect of cell growth and reproduction, if you get old enough, your chances of getting cancer increase regardless. It’s like me asking you to hand-copy my article one thousand times, the first few times will be perfect, but you’ll get riddled with mistakes by the 900th. In that sense, even the life sustaining oxygen from plants can trigger cancer because oxygen gives free radicals that cause DNA damage. We can’t live without it, can’t live too long with it either. Thus, keep a healthy lifestyle and live your limited time here on Earth to your best. As for carbon dioxide, you will be well aware of its toxicity because carbon dioxide causes suffocation sensation in humans. If the level of carbon dioxide is too high, your blood becomes acidic, and your lungs and kidneys will automatically work to eliminate them. Your brain will command your lungs to ventilate more, while your kidneys will turn extra carbon dioxide into bicarbonate (baking soda), which is alkaline and it keeps your blood pH in check, always at ~ pH 7.4. Even if you have a totally enclosed room, you’re more likely to suffocate from your own (exhaled) carbon dioxide than that from a meager plant.

Zamia furfuracea (Zamiaceae). Note the similatiry to Zamioculcas and hence it's Latin name.

Finally, where did all the ZZ myth come from? While I can’t be entirely sure, I think I might have an answer. If you analyse the name of Zamioculcas zamiifolia in Latin, it literally translates as ‘Zamia-like-leaves, Colacasia-like plant, with Zamia like leaves!’ I guess most of us know what’s Colacasia but what’s Zamia? That leads us to the answer! Zamia is a non-flowering plant, which is closely related to Cycads. If you've following my [Poison Garden], Zamia is way more toxic than Zanzibar gem and yes, cancer-causing if ingested. Zamia also causes chronic irreversible brain damage and liver toxicity to animals and occasionally humans that consumed it. I've talked about the precise mechanism of its toxicity in the cycasin article of the [Science] section, so check that out if you're interested.

 

I hope I have put a permanent GG to the ZZ myth!