188 Autism and Exposure to Environmental Chemicals
toxic to humans and other biological life forms. They emulate the scent of deer
musk or ox musk, but chemically they are not like the natural musk. Synthetic
musks have a clean, smooth, and sweet scent lacking the animalic notes of
natural musks. These compounds are an essential part of modern perfumery
and form the base note foundations of most perfume formulas. Currently,
almost all musk fragrances used in perfumery today are synthetic. There are
three different types of synthetic musks: aromatic (a nitro musk with a similar
structure to TNT explosive), polycyclic, and macrocyclic rings – all chemicals
known to be highly toxic, especially to fetal brain neurons. Musk xylene and
musk ketone are nitro musks. Nitro musks were a main ingredient in many
perfumes and other consumer products, however, concerns raised regarding
their bioaccumulation, toxicity to various life forms, and persistence in the
environment has led to reduced production in EU nations [67]. For example,
between 1995 and 2000, the total use of nitro musks amounted to 300 t (tons),
but then declined to 200 t [68]. On the other hand, the production of the poly
cyclic musks galaxolide and tonalide has increased significantly and they are
the mostly widely used today [69,70]. In fact, over 4,000 t of polycyclic musk
was sold in 2005 [71].
Synthetic musks are rarely listed on the label of products or tested for safety,
including testing for effects on unborn fetuses or on rapidly developing off
spring, since they are exempt according to the Federal Fair Packaging and
Labelling Act of 1973 [42]. Synthetic musks are found in many common house
hold detergents, soaps, perfumes, shampoos, air fresheners, and cosmetics
(reviewed in Refs [67, 68]). Originally introduced as cheap substitutes for natu
ral musk fragrances obtained from the musk deer and musk ox, synthetic
musk fragrance consumption leapt in the 20th century and was estimated to
be 8,000 t/year in 1996 [67]. In Europe in 1995 the combined usage rate of the
two most commonly used synthetic musk compounds, HHCB (1,3,4,6,7,8‐
hexahydro‐4,6,6,7,8,8‐hexamethylcyclopenta‐γ‐2‐benzopyran) and AHTN
(7‐acetyl‐1,1,3,4,4,6‐hexamethyl‐1,2,3,4‐tetrahydronaphthalene), was about
15.5 mg/day [69]. Additionally, the US EPA lists HHCB as a high production
volume chemical (more than 1 million pounds produced or imported into the
USA each year). Synthetic musks accumulate in the environment (i.e., in waste
water), fish, shrimp, and bioaccumulate inside humans (e.g. in body fat, blood,
human breast milk, and umbilical cords), similar to PCBs and organochlorine
pesticides [72–76]. It is well documented that synthetic musks can disrupt
human endocrine systems (hormonal functions and other physiological pro
cesses) [72–76]. They are highly ubiquitous in our daily life and are commonly
found in perfumes, colognes, soaps, body wash, sprays, lotions, hair products,
detergents, softeners, air fresheners, and in the environment. It is likely that
they may be present in some children’s medicines to make them more palata
ble. They are listed as “fragrance,” phantolide, celestolide, transeolide, cash
meran, musk ketone, musk xylene, galaxolide, tonalide, and so on.