By 1960 it was obvious that something was killing birds
and fish in startling numbers. It would
be Rachel Carson who would piece together the clues and unravel the science in
order to indict pesticides, their manufacturers, and their users for these
deaths. Meehan Crist paid homage to
Carson for her accomplishments and issued a warning that such threats continue
in an article for the London Review of Books: A Strange Blight.
Rachel Carson published Silent Spring in
1962. Crist provides this perspective.
“Following the scattered clues
wherever they led, Carson painstakingly pieced together an unassailable case
against chemical pesticides, then being indiscriminately dumped over field and
stream in white clouds, and in smaller but more intimately toxic loads by
American housewives cultivating their gardens and moth-proofing their babies
blankets.”
“Silent
Spring demonstrated, with scientific rigour and in
heart-thumping prose, that chemical pesticides were not just poisoning their
intended insect or weed targets, but accumulating in living cells, where they
altered essential cellular machinery, interacted in unpredictable ways, and
mutated genes in a heritable waterfall of damage that was warping the entire
‘web of life’.”
This was accomplished without assistance from the scientific
infrastructure and the vast datasets that are available today.
“The scientific achievement
of Silent
Spring is less often heralded. By making connections across
disciplines Carson inferred the way chemical pesticides disrupt endocrine
function and lead to tumour formation before any of this was established
science.”
It would be her book that would drive the
development of environmental science for succeeding generations.
“Rarely has the work of a single
author – or, indeed, a single book – had such an immediate and profound impact
on society. Silent Spring was the first
book to persuade a wide audience of the interconnectedness of all life,
ushering in the idea that ‘nature’ refers to ecosystems that include humans. It
spurred the passage in the United States of the Clean Air Act (1963), the
Wilderness Act (1964), the National Environmental Policy Act (1970), the Clean
Water Act (1972) and the Endangered Species Act (1973). Perhaps most
significant, it showed how human health and well-being ties in with the health
of our environment, leading to the establishment of the Environmental
Protection Agency in 1970. No wonder, then, that writers, activists and
scientists concerned about the ongoing destruction of biodiversity and the
catastrophic effects of climate change look to Carson with urgent nostalgia.”
Crist feels a need to remind us of what Carson, one
person, had accomplished, perhaps wishing that a new champion might appear. The environmental threat from continued use
and misuse of ever more new chemicals is now accompanied by the environmental
threats presented by a warming Earth.
Animal die-offs continue and while the mechanisms are not always well
understood, it is clear the cause is human activity. While considering the lack of progress in
countering carbon buildup in the atmosphere, she casually lets this thought
drop.
“But maybe humans won’t be
around to see the effects of the changes we have wrought on the biosphere. The
postwar chemical revolution that produced pesticides has also led to a dramatic
drop in male fertility. Because we are all ingesting chemicals that mess with
human hormones, sperm counts in men around the world have dropped by 50 per
cent in the last four decades – men today are half as fertile as their grandfathers
were. If this downward trend continues, as it seems to be doing, humanity may
be incapable of unassisted reproduction within decades. The social consequences
stagger the imagination. This trend towards male sterility is being driven by
endocrine disruption at the cellular level, which Carson linked to toxic
chemicals in Silent Spring. ‘Not all robins
receive a lethal dose,’ she writes, ‘but another consequence may lead to the
extinction of their kind as surely as fatal poisoning. The shadow of sterility
lies over all the bird studies and indeed lengthens to include all living
things within its potential range’.”
The notion that male sperm counts were falling in the
wealthy societies of Europe and North America was well established. More recently, data has emerged indicating
the phenomenon is worldwide and it is continuing. And it is
not just the sperm count that is affected, it is also the motility of the
sperm, its ability to move around, that has also been diminished. Something is changing the very nature of the
sperm, not just its concentration.
Crist’s suggestion that this trend could be an existential
threat is startling, but not unreasonable.
Humans and other mammals have the same organs and biochemistry. If animal species are dying off and becoming
extinct, there is no reason why humans wouldn’t be subject to the same threats.
Rachal Carson’s work did produce changes in behavior with
chemicals that were beneficial at the time.
However, since that period many more new chemicals have come into use
than can possibly be studied and evaluated, let alone try to understand how
they might behave in concert. And every
chemical we use eventually ends up in our water systems. Every shower we take washes chemicals that we
have applied to our bodies or have just settled on us, into our waterways. Every flush of the toilet sends residue from
every pill, lozenge, liquid, and food item we have consumed into that same
system. Every rainstorm sweeps up the
chemicals we dripped, poured, or sprayed onto the landscape into our water supply. Our treatment systems are not designed to
remove those chemicals, so they continue to build up and become more
dangerous.
There are plenty of indications that the chemicals that
mess with or mimic hormones, endocrine disrupters, exist at a level that can
harm fish. This source provides
this definition of endocrine disrupting chemicals (ECBs).
“Found in many household and
industrial products, endocrine disruptors are substances that ‘interfere with
the synthesis, secretion, transport, binding, action, or elimination of natural
hormones in the body that are responsible for development, behavior,
fertility, and maintenance of homeostasis (normal cell metabolism)’.”
We are not allowed to experiment on humans, but data on
other animals tells us that this complex chemical stew we now find in our
environment is dangerous.
“Studies in cells and laboratory
animals have shown that EDCs can cause adverse biological effects in animals,
and low-level exposures may also cause similar effects in human beings. EDCs in the environment may also be related
to reproductive and infertility problems in wildlife and bans and restrictions
on their use has been associated with a reduction in health problems and the
recovery of some wildlife populations.”
Not all the problems with EDCs are reproductive in
nature.
“In 2015 the Endocrine Society released
a statement on endocrine-disrupting chemicals (EDCs) specifically listing
obesity, diabetes, female reproduction, male reproduction, hormone-sensitive
cancers in females, prostate cancer in males, thyroid, and neurodevelopment and
neuroendocrine systems as being affected biological aspects of being exposed to
EDCs.”
And this is the most frightening aspect of EDCs.
“The critical period of
development for most organisms is between the transition from a fertilized egg
into a fully formed infant. As the cells begin to grow and differentiate, there
are critical balances of hormones and protein changes that must occur. Therefore,
a dose of disrupting chemicals may do substantial damage to a developing fetus.
The same dose may not significantly affect adult mothers.”
Fish inhabit our water sources. Since they are generally smaller than us but
have the same biochemistry, one might expect their fate to be a harbinger of
the fate of humans as the chemicals continue to build up in our waters. The existence of “intersex” has become common
in fish species. This source
provides a definition of that term.
“Intersex people are individuals
born with any of several variations in sex characteristics including
chromosomes, gonads, sex hormones, or genitals that, according to the UN Office
of the High Commissioner for Human Rights, ‘do not fit the typical definitions
for male or female bodies’.”
If intersex is becoming more common in fish, might one
expect the same to be occurring in humans?
This study, The Increasing Prevalence in Intersex Variation from Toxicological Dysregulation in Fetal Reproductive Tissue Differentiation and Development by Endocrine-Disrupting Chemicals, provided
by the National Institutes of Health seems to believe that is the case.
“An
increasing number of children are born with intersex variation (IV; ambiguous
genitalia/hermaphrodite, pseudohermaphroditism, etc.). Evidence shows that
endocrine-disrupting chemicals (EDCs) in the environment can cause reproductive
variation through dysregulation of normal reproductive tissue differentiation,
growth, and maturation if the fetus is exposed to EDCs during critical
developmental times in utero. Animal studies support fish and reptile embryos
exhibited IV and sex reversal when exposed to EDCs. Occupational studies
verified higher prevalence of offspring with IV in chemically exposed workers
(male and female).”
This paper also suggests that EDC exposure of males can
affect the development of a fetus, presumably by altering the quality of sperm
produced.
It turns out that Canada has a lake it reserves for
environmental experiments. One of its
recent studies involved exposing a species of fish to a level of EDCs found in
our now polluted waterways to determine the effect on the evolution of that
species. The results are found in Collapse of a fish population after exposure to a synthetic estrogen.
“We conducted a 7-year,
whole-lake experiment at the Experimental Lakes Area (ELA) in northwestern
Ontario, Canada, and showed that chronic exposure of fathead minnow (Pimephales
promelas) to low concentrations (5–6 ng·L−1) of the potent
17α-ethynylestradiol led to feminization of males through the production of
vitellogenin mRNA and protein, impacts on gonadal development as evidenced by
intersex in males and altered oogenesis in females, and, ultimately, a near
extinction of this species from the lake. Our observations demonstrate that the
concentrations of estrogens and their mimics observed in freshwaters can impact
the sustainability of wild fish populations.”
If the fish are beginning to go, can humans be far
behind?
Yes, we do face existential threats, and there is no
Rachel Carson out there worrying about us.
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