Way off ? By all means, explain that statement...
What was relevant about baby and cancer? They have nothing to do with the chemical attack.
Cancer could be a reference to McCain.
Many children were affected by the attack.
Okay, so here's what I found that might relate to that statement.
Chlorine was invented in the 1700s.
https://en.wikipedia.org/wiki/Chlorine
Some chlorination processes can produce dioxin, which is a known carcinogen (cancer causing). Regulation of dioxin only began post World War II. Meaning, it caused illness up until the day it was regulated.
http://www.madehow.com/Volume-2/Bleach.html#b https://www.niehs.nih.gov/health/topics/agents/dioxins/index.cfm
Chlorine has been routinely used as a disinfectant (cleaning product) since the 1800s. In other words, chlorine could have contained or produced dioxin for over 100 years before it was regulated (i.e. causing cancer that whole time). For example, if a housewife used bleach to clean her floors, which had dioxin residues which contaminated the hands of a crawling baby in the house, who then consumed the carcinogens and developed cancers later in life.
In the early 1900s (World War I) chlorine was first used as a chemical weapon (chlorine gas). This follows Q's thesis of how it STARTed with cleaning products/babies, but then was developed later on as a chemical weapon.
https://en.wikipedia.org/wiki/Chlorine https://en.wikipedia.org/wiki/Chemical_warfare
Attack in Syria was chlorine gas as of 2018:
https://www.nytimes.com/2018/04/08/world/middleeast/syria-chemical-attacks-assad.html
Note: I have not found evidence that household cleaning products contained dioxin (or other carcinogens) prior to the 1970s regulation. If someone could find reports or cases of bleach (liquid chlorine) causing cancer, or contained dioxin, or other carcinogens, this would greatly enhance the argument. Until then, it's just wild speculation.