Can Med Assoc J, Jan 1, 1997;
156 (1): 37-41
Declining sex ratios in
Canada
by Allan BB, Brant R, Seidel JE, Jarrell
JF
Objective:
To examine the trends in the proportion of annual live births
that were male in Canada and to compare the trends with
those in the United States,
Design:
Analysis of census data.
Setting:
Canada as a whole and 4 main regions (West, Ontario, Quebec
and Atlantic)
Subjects:
All live births from 1930 to 1990
Outcome measures:
Sex ratio (expressed as the proportion of total live births
that were male (male population) overall and by region
Results:
The male proportion in Canada decreased
significantly after 1970 (p <0.001);
this represented a cumulative loss of 2.2 male births per
1000 live brths from 1970 to 1990. Although a decrease was
observed in all four regions studied, only
that in the Atlantic region was significant (p <0.001),
representing a cumulatve loss of 5.6 male births per 1000
live births from 1970 to 1990. A significant decrease
in the male proportion was also observed in the United States
from 1970 to 1990 (p <0.001), although to a
lesser degree than that observed in Canada, and represented
a cumulative loss of 1.0 male births per 1000 live births.
Conclusions:
The decreased sex ratio in Canada adds to the growing debate
over changes in biological markers and their potential causes.
In addition, the study illustrates the potential use of
the sex ratio as a widely available, unambiguous measure
of the reproductive health of large populations.
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The
use of high doses increases the likelihood that potentially
significant toxic effects will be identified. Findings of
adverse effects in any one species do not necessarily indicate
such effects might be generated in humans. From a conservative
risk assessment perspective however, adverse findings in
animal species are assumed to represent potential effects
in humans, unless convincing evidence of species specificity
is available.
--
Food and Agricultural Organization of the United Nations
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Note:
This is not an exhaustive list.
When time allows more information will be added.
Fipronil
- Acaricide,
Insecticide
- CAS No. 120068-37-3
Abstract: Copepods
are the most abundant arthropods on earth and are often the most
important secondary producers in estuarine/marine food webs. The
new GABA (gamma-aminobutyric acid)-disrupting insecticide fipronil
(FP) induces unique sex-specific reproductive dysfunction in male
meiobenthic copepods, leading to trans-generational population
depression at environmentally realistic concentrations (0.63 microg/L).
Using a newly developed 96-well microplate lifecycle bioassay,
more than 700 individual Stage-I juveniles were reared to adulthood
in as short as 12 days in only 200 microL of control (CTL) or
0.63 microg-FP/L seawater solution. Individual virgin male: female
pairs were then cross-mated for all possible combinations within
and across rearing treatments and allowed to mate for an additional
12 days in CTL or 0.63 microg-FP/L solution. FP at 0.63 microg/L
caused no significant lethality to any mating combinations but
evoked 73% or 89% inhibition of reproduction when FP-reared males
were mated with either a control- or FP-reared female in FP solution,
respectively. In contrast, when CTL-reared males were mated with
FP-reared females in FP solution, there was no difference in reproductive
success compared to FP-free controls. When FP-reared males were
mated with either female group in FP-free solution, these mating
pairs displayed a 3-day delay in time to brood sac extrusion but
ultimately did reproduce. As fipronil (1)
has a high K(ow), (2) is persistent in sediments where meiobenthic
copepods live, and (3) has been detected in estuarine waters >0.7
microg/L, it may pose high risk to copepod production in estuarine
systems.
Ref:
Environ Sci Technol. 2004 Jan 15;38(2):522-8. Phenylpyrazole insecticide
fipronil induces male infertility in the estuarine meiobenthic
crustacean Amphiascus tenuiremis; by Cary TL, Chandler GT, Volz
DC, Walse SS, Ferry JL.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=14750729
Flonicamid
- Insecticide - CAS No.
158062-67-0
-- TERATOLOGY, RABBIT
Rangefinding Study: 52964 - 0060 216034 “IKI-220 Technical:
A Teratogenicity Study in Rabbits Preliminary Study,” (Takahashi,
K.; Institute of Environmental Toxicology, Ibaraki, Japan; Laboratory
Study #: IET 000024; 2/21/02). Flonicamid technical (98.7% pure)
was administered via oral gavage to artificially inseminated SPF
Japanese White rabbits (Kbl:JW) (6/dose)
at 0 (1% sodium carboxymethyl cellu- lose), 3, 10 and 30 mg/kg/day
during gestation days 6 through 27. Maternal NOEL = 10 mg/kg/day
(There were slight effects on body weight, body weight gain, clinical
signs, abortion (2/6 does at 30 mg/kg), food consumption, gravid
uterine weights and placental weights at 30 mg/kg/day.) Developmental
NOEL = 10 mg/kg/day (There were lowered
sex ratios, and fewer implants and live fetuses at 30 mg/kg/day.)
There were no major deficiencies in this study. It was for the
purpose of dose rangefinding for the definitive study. No adverse
effect indicated. These data are supplemental. Silva, 2/10/05
Definitive Study:
Reference:
April 28, 2005 - Summary of toxicology data. California EPA, Department
of Pesticide Regulation, Medical Toxicology Branch.
http://www.fluorideaction.org/pesticides/flonicamid.ca.epa.2005.pdf
TFM
(3-Trifluoro-Methyl-4-Nitro-Phenol) - Lampricide, Piscicide
- CAS No. 88-30-2
Note
from FAN: The use of TFM in the
Great Lakes began at the end of the 1950's. The chief outlet
of the Great Lakes is the St. Lawrence River, which flows northeast
from Lake Ontario to the Gulf of St. Lawrence on the North Atlantic
Ocean. Since the introduction of TFM in the Great Lakes there
has been a dramatic and significant shift from male to female
sea lampreys. A confounding factor may be that TFM was found
to be contaminated with dioxin in the early 1990s. It is unclear
whether dioxin influenced this alteration, or TFM alone, or
the combination of TFM and dioxin. Also it is unclear when the
dioxin contamination of TFM began. If you know, please contact
me and I will share the information. Thanks. EC. Sept. 2003.
-- TFM treatments have
been associated with induction of hepatic mixed function oxyganase
activity and altered levels of circulating
steroids in fish and induced hepatic
vitellogenesis in primary cultures of rainbow trout hepatocytes
(Hewitt et al. 1997). As such, TFM acts as an
estradiol agonist and has a demonstrated
endocrine disrupting effect...
-- Abundance
of sea lamprey peaked in several Great Lakes before chemical control
began. The sex ratio in these peak
populations were predominately males (68-71%). Following
a decade of lampricide treatments, populations of sea lampreys
showed marked declines and the sex ratios
in these populations shifted toward a predominance
of females accounting for 72% of the population (Henrich,
et al, 1979). This publication by Henrich concludes that lampricides
reduced the populations of sea lampreys in the Great Lakes and
contributed to the sequential shifting of
the sex composition from a predominance of males to a predominance
of females. There are no data to support that the endocrine
mediated effect associated with TFM is related to the observed
sex-ratio shifts among TFM-treated populations of sea lamprey
[page 23].
Ref: November 1999 US EPA's Reregistration
Eligibility Decision (RED) for 3-Trifluoro-Methyl-4-Nitro-Phenol
and Niclosamide). http://www.fluoridealert.org/PESTICIDES/TFM.Red.1999.pdf
Abstract: Growth and
age at metamorphosis were determined for populations of larval
sea lampreys that became reestablished after chemical treatments
of tributaries of Lakes Superior and Michigan (USA) with the selected
lampricide, 3-trifluoromethyl-4-nitrophenol. Age at metamorphosis
varied from 3-7 yr. Growth of ammocetes varied considerably from
stream to stream and within streams. Mean lengths of ammocetes
of age group III in late summer or early fall in different streams
ranged from 65-144 mm. Ammocetes of the 1st yr class established
after a chemical treatment grew faster than those of succeeding
year classes. Transformation at an early age usually occurred
only among fast-growing larvae in large streams.
A reversal of the sex ratio, from predominately male to predominately
female, followed the reduction of the adult sea lamprey population.
Sex ratios of larval and recently metamorphosed sea lampreys reestablished
after chemical treatments rapidly shifted from an excess of males
to an excess of females. The shift in sex ratio was related
to decreased densities of sea lampreys resulting from treatments.
Ref: PURVIS HA (1979).
Variations in growth, age at transformation, and sex ratio of
sea lampreys (Petromyzon marinus) reestablished in chemically
treated tributaries of the upper Great Lakes (USA). GREAT LAKES
FISH COMM TECH REP; 0 (35). 1-36.
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