Front Matter

28 Introduction to Autism Spectrum Disorders

of the ASD brain are the amygdala, frontal lobe, thalamus, hypothalamus, and

hippocampus. Also, there is a typical loss of olfactory bulb capacity that results

in a significant reduction in the ability to smell.

What agents could potentially act as ASD causative factors? Our research

indicates that every one of the 98 fragrances we tested using the Ames test, a

gold standard to detect carcinogens and mutagens and required by FDA as one

of the safety tests, induced fetal brain mutations at the cellular level, even with

dilutions as small as 1:50,000 [10]. This suggests that synthetic chemical expo­

sure levels that may appear innocuous are not harmless to highly vulnerable

fetal brain cells, and that significant fetal mutations may be linked to such

exposure. However, we do not believe that these mutagenic agents are respon­

sible for ASD directly. We believe that these ASD unrelated mutations, thou­

sands of those SNPs and CNVs, are erroneously claimed to cause ASD.

In  reality, they are just associated mutations and not the cause of ASD. We

emphasize the point that over 4,000 synthetic chemicals are used, collectively,

123 45678916 20–36

Period of dividing zygote, Embryonic period, weeks Fetal period, weeks

implantation and embryo,

weeks

Palate Ear Brain

Palate

Ear

Ear

Eye

Eyes

Eye

Eye

Heart

Heart

Upper limbs

Lower limbs

Not susceptible to teratogens

Prenatal death Major congenital anomalies (red) Functional defects and minor congenital anomalies

Central nervous system

Teeth

External genitalia

Heart

38

External genitalia

Figure 1.16 Developmental progression and susceptibility to teratogens and fetal loss. The

bars indicate periods when organs are most sensitive to damage from teratogenic agents.

Note that in most literature development of the olfactory system is missing. The brain starts

developing 18 days after fertilization. Often women do not know that they are pregnant

until after a few weeks have passed. Therefore, pregnant women who are exposed to certain

synthetic fragrances, either through inhalation or epidermal exposure, and food‐flavor

chemicals, through ingestion (e.g., teas, chewing gum, and other food flavors), may put

their embryo at risk without even knowing it. Source: Adapted from Ref. [8]. (See insert for

color representation of this figure.)