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WEST NILE VIRUS, Part 1
by Rachel Massey
West Nile virus (WNV), a disease previously unknown in the Western Hemisphere, appeared in New York City last year and has now spread to animal populations in six other states. Some municipal officials have responded to the disease by spraying entire neighborhoods with pesticides intended to kill mosquitoes. West Nile Virus can cause serious illness and death in some cases, but spraying pesticides to kill mosquitoes is not a good solution. Spraying exposes large numbers of people to toxins with both short- and long-term health effects, and studies suggest it is unlikely to be effective.
Transmitted by mosquitoes, WNV primarily attacks birds but can also infect humans and other animals. Most infections with WNV go unnoticed or feel like an ordinary flu, but some cases lead to encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes surrounding the brain and spinal cord) and can be fatal. The elderly and individuals with compromised immune systems may be particularly vulnerable to serious illness resulting from the virus.
In 2000, WNV has reappeared in New York City, and infected birds have been found in upstate New York as well as New Jersey, Massachusetts, Rhode Island, New Hampshire, Connecticut, and Maryland.[1] In the 1999 outbreak, sixty-two people became seriously ill and seven died. The individuals who died of the virus ranged from 68 to 87 years of age.[2] Of the fifty-five individuals in New York City who survived severe cases of the virus, some continue to suffer neurological problems a year later.
As of October 7, a total of 17 human cases of WNV had been detected this year, 3 in New Jersey and 14 in New York.[4] One individual, an 82-year-old man in New Jersey, has died of the virus this year.[5] Recent outbreaks have occurred in other countries as well; in Israel, over 120 people have shown symptoms of WNV infection this year and 10 have died.
In a study conducted last summer, researchers tested blood from 677 randomly selected individuals in a 4-square-mile area around the focal point of the outbreak in Queens, N.Y. Of these 677, 19 showed evidence of having been infected with West Nile virus. Based on these results, the researchers estimated that 2.6% of the individuals in the area studied were infected with the virus. About a fifth of these exposed individuals had experienced symptoms attributable to the virus. This study supports the view that most individuals infected with the virus never develop noticeable symptoms.[7] The Centers for Disease Control (CDC) estimates that the case-mortality rate for WNV (the proportion of individuals showing symptoms who die of the disease) is three to fifteen percent, with the fifteen percent figure applying to the elderly.
Mosquitoes begin life as eggs laid in stagnant water; later they change into water-dwelling larvae, then pupae, and finally adults. Thus they can be controlled by several means -- by minimizing standing water, by maintaining populations of egg- or larva-eating fish, or by applying chemicals that kill either larvae or adults.
New York City responded to the appearance of the virus last year by spraying the organophosphate insecticide malathion from trucks and helicopters to kill adult mosquitoes. Organophosphates act as nerve toxins, disrupting the nervous system by inhibiting the enzyme cholinesterase. Short-term symptoms resulting from human exposure to organophosphates can include breathing problems, headache, nausea and dizziness. High exposures can produce fatal poisoning.[9] In April 2000, a U.S. Environmental Protection Agency (EPA) committee reviewed a series of studies on mice and rats exposed to malathion. Based on this review, the committee concluded that there was "suggestive evidence of carcinogenicity" which was "not sufficient to assess human carcinogenic potential."[10] For the moment malathion remains listed by EPA as "not classifiable" with regard to carcinogenicity. Malathion is also a suspected hormone disrupter.
This year, New York and other municipalities have used pyrethroid insecticides such as Scourge (active ingredient, resmethrin) and Anvil (active ingredient, sumithrin) to kill adult mosquitoes. The pyrethroids also act as nerve toxins, and may have other long-term health effects. Resmethrin has been found to act as a weak hormone mimic in test tube studies.[12] A 1999 study on how pyrethroids affected breast cancer cells in a laboratory setting led researchers to suggest that the pyrethroids as a group should be considered hormone disrupters.[13] EPA is scheduled to re-evaluate the health effects of the pyrethroids in 2002.
Pyrethroids are also very toxic to fish and to bees, and there are regulations against applying them on or near bodies of water.[14] It is particularly important to pay attention to their effects on fish when designing a mosquito control program, since healthy fish populations can serve as an important natural mosquito control.
Like several other pyrethroid insecticides, Scourge and Anvil contain piperonyl butoxide (PBO), which is added to enhance the toxicity of the active ingredients. Studies have linked PBO exposure to liver cancers in rats and mice,[15] and it is classified by the EPA as a possible human carcinogen. There is also some evidence that PBO-pyrethroid mixes can affect the human immune system.
Intentionally spraying thousands of people with suspected carcinogens or hormone disrupters seems dubious from a public health perspective. Potential effects on fetuses, infants, and children are of particular concern. Increasing evidence supports the view that even tiny exposures to toxic chemicals can have devastating effects on infants and developing fetuses, depending when the exposures occur.
There has been considerable variation in responses to WNV this year. When infected birds began appearing in the Boston area, several municipalities began aggressive spraying to kill adult mosquitoes in an area defined by a two-mile radius around the site where an infected bird was found. Buffalo, N.Y., on the other hand, has limited itself to the use of larvicides placed in standing water without spraying.[18]
Some municipalities have used chemical larvicides such as Altosid (active ingredient, methoprene), to kill mosquito larvae in catch basins and other standing water. When exposed to sunlight, methoprene breaks down into a class of chemicals closely related to vitamin A, known as retinoids, which can cause birth defects in humans and may be contributing to the global epidemic of skeletal deformities in frogs (see REHW #590 and #623 ). Other municipalities have opted for least-toxic control measures, including the use of BACILLUS THURINGIENSIS ISRAELENSIS (BTI) and BACILLUS SPHAERICUS , naturally-occurring bacteria that are toxic to mosquito larvae.
Long-term health effects of spraying pesticides in urban areas are probably the greatest concern, but acute exposures can also be a problem. Municipal officials in charge of spray programs in New York and other cities warned residents to remain indoors during the scheduled spray times, closing windows and turning off air conditioners to prevent the chemicals from entering their homes. But in one case, a New York resident was sprayed at close range when trucks began spraying at 10:00 pm rather than at midnight, as they had been scheduled to do.[19] At an April, 2000 meeting in New York, several people said they thought they were suffering neurological problems resulting from the spraying, and one doctor said she had seen 160 patients with minor neurological problems possibly attributable to the spraying.
HERE WE GO AGAIN: PHTHALATES
Several new studies indicate that common industrial chemicals called phthalates (pronounced tha-lates) in food and water may be interfering with development of the reproductive system in both boys and girls.
** For 20 years, large numbers of baby girls in Puerto Rico between the ages of six months and 2 years have been experiencing premature breast development, a condition called precocious thelarche (pronounced thee-larky). Since 1970, there have been 4674 cases of precocious thelarche recorded in Puerto Rico, where the condition is now occurring in 8 out of every 1000 baby girls, or just under 1%. Compared to a group of baby girls studied in Minnesota, precocious thelarche in Puerto Rico is 18 times as prevalent.
For 20 years, scientists have tried to link the alarming epidemic in Puerto Rico to artificial hormones in meat, pharmaceutical manufacturing wastes, and infant formula containing high levels of phytoestrogens (plants that contain natural estrogen-like chemicals), but no satisfactory explanation has emerged. Now researchers have found evidence linking precocious thelarche to common phthalates.[1,2]
Blood samples from two groups of girls in Puerto Rico -- 41 baby girls with precocious thelarche and 35 with normal development -- were examined for pesticides and phthalates. Pesticides were not found in either group. Phthalates were present in the blood of 68% of the precocious thelarche group and 14% of the control group. Phthalates tend not to bioaccumulate, so phthalates measured in blood are likely to reflect current exposures, not past exposures.
Phthalates are common industrial chemicals used in building materials, food packaging and food wrap, toys and other children's products, medical devices, garden hose, shoes, shoe soles, automobile undercoating, wires and cables, carpet backing, carpet tile, vinyl tile, pool liners, artificial leather, canvas tarps, notebook covers, tool handles, dishwasher baskets, flea collars, insect repellents, skin emollients, hair sprays, nail polish, and perfumes.
(The Environmental Health Network in California has petitioned the U.S. Food and Drug Administration to require labeling of perfumes that contain toxic phthalates, such as Calvin Klein's Eternity. See http//:users.lanminds.com/~wilworks/- FDApetition/fdapetit.htm.)
One particular phthalate -- di-(2-ethylhexyl) phthalate, or DEHP -- accounted for 88% of the total phthalates measured in the precocious thelarche group and 80% of the total phthalates in the control group. The average levels of DEHP in the control group were 70 ppb and in the precious thelarche group 450 ppb -- more than six times as great.
Some phthalates mimic estrogen (female sex hormone) and others interfere with androgen (male sex hormone).[3,4,5] In laboratory animals, some phthalates can cause birth defects and can disrupt hormones, leading to altered sexual development. Regarding reproductive and developmental effects in laboratory animals, phthalates vary in potency, with DEHP being about 10 times as potent as the other phthalates.[6]
The average daily consumption of DEHP by children in the U.S. is estimated to be 5.8 milligrams per day.[1] The most important source of DEHP exposure is contaminated baby formula, food and water contaminated by contact with plastic containers and food wrap, and plastic toys and pacifiers made soft by the addition of DEHP. Because Puerto Rico is an island, above-average quantities of prepared foods are shipped there packaged in phthalate-containing plastics.
This small study does not prove that phthalates are causing premature sexual development among baby girls in Puerto Rico, but, combined with what is known about phthalates from laboratory animal studies, it provides a strong suggestion that phthalates may be contributing to the epidemic.
To maintain current awareness of phthalates and other endocrine-disrupting chemicals, check back regularly at https://- www.ourstolenfuture.org.
** A very recent study reveals that phthalates are present in the blood of adult Americans "at levels we are concerned about," according to John Brock, a chemist with the federal Centers for Disease Control (CDC) in Atlanta. Brock and his colleagues studied phthalates in the blood of 289 adults and found levels "higher than we anticipated."[6,7]
Many laboratory products (such as plastic tubing) contain phthalates. As a consequence, phthalates are often found in samples analyzed in laboratories because lab equipment contaminates the samples. For the past decade, scientists have been finding phthalates in human tissue samples, but they have assumed they were measuring lab contamination. Consequently, no one has raised an alarm about phthalates in adult humans, until this month.
To measure phthalates in human urine, Brock and his colleagues developed specialized techniques for identifying metabolic byproducts of phthalates; in other words, they learned how to measure the chemicals that are produced when phthalates are processed by a human liver and kidney. By this means, Brock could be sure his team was measuring human exposures to phthalates and not merely contamination introduced into samples from laboratory equipment.
Brock tested for and found seven phthalate metabolites in human urine. The four phthalate metabolites found at the highest levels came from DEHP, DEP (diethyl phthalate), BzBP (butyl benzyl phthalate) and DBP (di-N-butyl phthalate). "From a public health perspective, these data provide evidence that phthalate exposure is higher and more common than previously suspected," Brock and his colleagues concluded.[6] They offered additional reasons for concern:
** The highest phthalate levels were measured among women of child-bearing age (20 to 40) -- about 50% higher than among groups of different age and gender.
** DEHP, DBP and BzBP are known to cause birth defects in laboratory animals. (Note that BzBP is sometimes known as butyl benzyl phthalate, or BBP.)
** DBP is toxic to the testicles.
** The metabolites of BzBP and DEHP that Brock measured are toxic to sertoli cells (the cells that produce sperm). Next month a new study will conclude once again that for three decades there has been a steady (1.5% per year) decline in the quantity of sperm produced by men living in industrialized countries.[8] No one knows if exposure to phthalates is involved in the decline.
** Administration of DBP and DEHP to pregnant rats interferes with the fetal development of male rats. DBP is widely used in perfumes, nail polishes, and hair sprays, allowing for efficient absorption through the lungs.
Phthalates were recently measured in baby food and infant formula.[9]
The National Research Council (NRC) (of the National Academy of Sciences) discussed two phthalates in its July, 1999, study of endocrine-disrupting chemicals (see REHW #665 ). The NRC noted that female rats exposed to BzBP in water prior to mating produced male offspring with significantaly smaller-than-average testicles, and reduced sperm counts.[10,pg.21] A subsequent attempt to reproduce this experiment failed to achieve the same results, for reasons that remain unknown.
The NRC also noted that DBP has been shown in several animal studies to cause atrophy of the testicles, and destruction of sertoli cells (the cells that produce sperm). A multigenerational study concluded that "DBP is a reproductive and developmental toxicant to both adult and developing rats and that DBP had greater effects on the second generation than [on] the first generation."[10,pg.122] A different study showed that pregnant rats dosed with DBP at a particular time during pregnancy produced offspring with significant incidence of undescended testicles.[10,pg.123] In humans in industrialized countries, the occurrence of undescended testicles (a condition called cryptorchidism) has been increasing in recent decades.
Dr. Louis Guillette, a University of Florida zoology professor and a member of the NRC committee that studied hormone-disrupting chemicals, says that Brock's study of phthalates in adults "is going to rewrite how we look at phthalates.... Phthalates have been something of concern up to this point. Basically they're going to leap upward in terms of concern."[7]
In the U.S., the National Institutes of Health (NIH) has created a new Center for the Evaluation of Risks to Human Reproduction (CERHR). In June of this year, a CERHR panel of experts concluded its evaluation of seven phthalates. Although the CERHR study has not yet been published, CERHR issued a press release July 14 in which they acknowledged that the panel of experts had expressed "concern" that exposure of pregnant women to DEHP might adversely affect the development of their offspring.[11] DEHP is the chemical measured in baby girls with precocious breast development in Puerto Rico.
As scientific and medical evidence accumulates, linking phthalates to reproductive disorders in humans, the chemical industry is digging in its heels for a 50-year fight. The industry produces a billion pounds of phthalates every year and has no intention of acknowledging that its products may cause birth defects, infertility or hormone disruption.
Because the chemical industry is so wealthy and donates huge quantities of cash to election campaigns (a perfectly legal form of bribery), in the U.S. there is almost no way to get rid of chemicals that have frightening characteristics, like phthalates. They are here to stay. "I can tell you that we're going to be working on phthalates for a long time here at CDC," says John Brock.[7] On the other hand, a citizen revolt could change the election financing system almost overnight and immediately reduce the political power of the chemical industry. Change is possible, but only if people get angry and get involved. (See www.publicampaign.org.)
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