What chemical agent can cause both nervous and reproductive effects?

Question

In a realistic dystopia, warring religious sects turn on each other using chemical warfare, resulting in mass destruction. Because of the nature of their beliefs, these sects avoid technology; thus, a chemical agent - and not a nuclear weapon - must be used.

The chemical agent in question should have the potential to be fatal and preferably exert its effects on the nervous system, with symptoms including seizures and paralysis. Long-term effects of exposure on survivors must include cognitive deficits, such as memory loss and visual disturbances, as well as motor deficits such as tremors and muscle weakness. Some survivors could become sterile, but at least a percentage must be capable of reproduction, with the potential of having offspring with birth defects.

Children of the survivors could have physical malformations, but cognitive and motor deficits are preferable. In other words, they should express similar symptoms to those caused by the chemical agent, such as decreased concentration and memory, poor reasoning skills, seizures or tremors, and impaired motor functioning. These deficits must be inherited maternally.

Two chemical agents that meet some, but not all, these requirements are mustard gas and sarin nerve gas. Mustard gas exerts a strong effect on reproduction, with a significant number of survivors either becoming infertile or producing children with birth defects. However, mustard gas causes chemical burns and scarring rather than affecting the nervous system. Moreover, it tends to affect the male reproductive system, but this agent must be capable of affecting female organs as well. Sarin nerve gas does affect the nervous system, resulting in the required cognitive and motor effects. However, it does not affect the reproductive system and children born to survivors are healthy physically and cognitively.

Is there an alternate chemical agent that combines these two properties, or a way to manipulate one of these two agents so that it exerts the desired effects? I would consider the method of dissemination (for instance, whether the gas is released as a vapor or liquid, and if it contaminates the food or water supply), and maybe tweaking the agent chemically as well. For the sake of realism, I don't want to fabricate a fictitious agent that meets these requirements.

What chemical agent could exert its effects on the central nervous system, and also result in survivors likely to produce offspring with cognitive and motor deficits?

Answer 1

Minamata disease.

https://en.wikipedia.org/wiki/Minamata_disease

Minamata disease is a neurological disease caused by severe mercury poisoning. Signs and symptoms include ataxia, numbness in the hands and feet, general muscle weakness, loss of peripheral vision, and damage to hearing and speech. In extreme cases, insanity, paralysis, coma, and death follow within weeks of the onset of symptoms. A congenital form of the disease can also affect fetuses in the womb and may cause cerebral palsy.

Sounds like all the badness you want. These people were poisoned by methylmercury discharged from a factory and contaminating their seafood. There is a lot written about Minamata disease if you require gory factual details.

Answer 2

These deficits must be inherited maternally.

That is not practical with a chemical weapon. In male humans, sperm are produced continuously, and their genes can thus be damaged by unwanted substances present in the body. However, in female humans, eggs are all formed by the time a woman is born or shortly thereafter. A chemical weapon can't selectively damage genes in un-fertilized eggs to produce particular effects: the necessary selectivity is impossible to engineer into a molecule light enough to be a gas at ordinary temperatures.

An engineered virus, on the other hand, is rather more practical. That can infect humans and interfere with nerve signalling, with a similar effect to nerve gasses. It needs to be capable of going into a latent state in females and being triggered by the characteristic hormones of pregnancy. Then it needs to get across the placental barrier and there are some viruses which can do that. Then it can attack the nervous system of the fetus, causing your desired deficits.

I doubt we could engineer such a virus today, but it doesn't seem basically impossible. It would take at least a decade of profoundly unethical development work; can your story accommodate that?