in root growth, nitrate production, ammonium production, and changes in the activities of nitrate reductase and nitrite reductase. at low doses of bpa, the growth of roots were improved, the amount of nitrate in roots increased, the amount of ammonium in roots decreased, and the nitrate and nitrite reductase activities remained unchanged. however, at considerably higher concentrations of bpa, the opposite effects were seen for all but an increase in nitrate concentration and a decrease in nitrite and nitrate reductase activities. nitrogen is both a plant nutritional substance, but also the basis of growth and development in plants. changing concentrations of bpa can be harmful to the ecology of an ecosystem, as well as to humans if the plants are produced to be consumed. the amount of absorbed bpa on sediment was also seen to decrease with increases in temperature, as demonstrated by a study in 2006 with various plants from the xiangjiang river in central-south china. in general, as temperature increases, the water solubility of a compound increases. therefore, the amount of sorbate that enters the solid phase will lower at the equilibrium point. it was also observed that the adsorption process of bpa on sediment is exothermic, the molar formation enthalpy, δh°, was negative, the free energy δg°, was negative, and the molar entropy, δs°, was positive. this indicates that the adsorption of bpa is driven by enthalpy. the adsorption of bpa has also been observed to decrease with increasing ph. a 2005 study conducted in the united states had found that 91–98% of bpa may be removed from water during treatment at municipal water treatment plants. a more detailed explanation of aqueous reactions of bpa can be observed in the degradation of bpa section below. nevertheless, a 2009 meta-analysis of bpa in the surface water system showed bpa present in surface water and sediment in the united states and europe. according to environment canada in 2011, "bpa can currently be found in municipal wastewater. initial assessment shows that at low levels, bisphenol a can harm fish and organisms over time." bpa affects growth, reproduction, and development in aquatic organisms. among freshwater organisms, fish appear to be the most sensitive species. evidence of endocrine-related effects in fish, aquatic invertebrates, amphibians, and reptiles has been reported at environmentally relevant exposure levels lower than those required for acute toxicity. there is a widespread variation in reported values for endocrine-related effects, but many fall in the range of 1μg/l to 1 mg/l. a 2009 review of the biological impacts of plasticizers on wildlife published by the royal society with a focus on aquatic and terrestrial annelids, molluscs, crustaceans, insects, fish and amphibians concluded that bpa affects reproduction in all studied animal groups, impairs development in crustaceans and amphibians and induces genetic aberrations. vertebrates bpa is known as an endocrine disruptor compound (edc) and has major neurological effects on vertebrates. depending on the vertebrate species studied, the documented effects of ingestion and exposure to bpa may differ. in species such as zebrafish, bpa affects the lateral line which is crucial for sensory perception and may affect the expression of genes that are controlling heart and skeletal muscle metabolism, as well as insulin secretion control. aquatic vertebrates are especially impacted by bpa in reproduction. in the broad- snouted caiman, caiman latirostris, gender is normally determined by the temperature at which the egg is incubated at. a study was conducted where their eggs were exposed to bpa. the first set was exposed at about 1000 µg/egg and all of the offspring were female. when the eggs were exposed at a lower concentration at about 90 µg/egg, the offspring produced were males. these male offspring exhibited disrupted seminiferous tubules. in mice, maternal diet has been studied and found to have a major effect on the offspring that were exposed to bpa during certain developmental stages. there are no direct studies on humans, however, studies on the vertebrates suggest the potential harm it may have. reproductive effects bisphenol a (bpa) is an environmental contaminant that disrupts the ecosystem, with the most profound effects observed in vertebrates. bpa infiltrates the environment by running off of landfills so because of this, it is mostly found in water. aquatic vertebrates are thus the most affected by this form of pollution. after the aquatic vertebrates inhale bpa through their gills or skin, they are mainly affected by bpa at the cellular level, affecting their estrogen levels. bpa binds to the estrogen receptors and has an antagonist effect, which means that it decreases the amount of estrogen produced. to regulate reproductive functions, gonadotropin releasing hormone (gnrh) is released. this helps with maturation of the sex organs in both males and females. another study found that barbus sp., immature barbels, in a river with traces of bpa expressed intersex characteristics. they had gonads with oogonia, spermatogonia and spermatocytes. researchers concluded that bpa did not induce but did contribute to these intersex morphological expressions. after being exposed to 1μg/l bpa, salmo trutta, brown trout, had reduced sperm density and mobility. in pimephales promelas, fathead minnows, there was a reduction of sperm production. both species were also exposed to 2 μg/l and 5 μg/l of bpa and it resulted in delayed ovulation or no ovulation for the fish. a study was conducted using adult female gobiocypris rarus, a rare minnow. the fish were exposed to 5 μg/l, 15μg/l and 50 μg/l of bpa for 14 days and 35 days. the results showed the group exposed to the highest amount of bpa (50 μg/l) for 35 days showed suppressed effects on oocyte development. it also showed that all groups had a stimulatory effect on the hepatic vitellogenin transcription (vtg). vtg is an indicator that the vertebrate has become exposed to environmental estrogens. the groups exposed to a lower concentration of bpa (5 μg/l & 15μg/l) showed an increase in expressed ovarian steroidogenic genes. meanwhile, the group exposed to a higher concentration of bpa (50 μg/l) showed a decrease in expressed ovarian steroidogenic genes. although aquatic vertebrates are most commonly affected by bpa exposure in natural settings, researchers often learn how bpa effects other vertebrates using experimental mice models. in a study conducted twenty years ago, there was an accidental bpa exposure. this resulted in an increase in chromosomally abnormal eggs. this led researchers to question what other effects this has on mammals. it showed that bpa leads to meiotic changes such as fertility and maturation of sex organs. scientists started to realize that this type of exposure could lead to mutations and affect multiple generations. because of this, "bpa free" products started to be made but to do this, bps was being used. a study was conducted showing that exposure to bps increased mutations before zygotic development showing that it is just as dangerous as bpa. behavioral effects bpa has major effects on the behavior of vertebrates, especially in their sensory processing systems. in zebrafish bpa can disrupt the signaling in the endocrine system and affect auditory development and function. similar to a human ear, the zebrafish have a sensory organ called the lateral line that detects different forms of vibration. the hair cells within the lateral line are very sensitive to the toxic effects of bpa and are most commonly killed from bpa; fish are able to regrow hair cells but bpa has decreased their ability to reproduce them as efficiently. fish without a fully functioning lateral line have behavioral changes such as: higher risk of predation, lowered prey detection and possible reproduction abilities. unlike fish, mammals have a threat to go deaf if exposed directly. as well as an endocrine disruptor compound (edc), bpa has been found to inhibit nerve conduction. in the sciatic nerve of a frog (rana tigrina), bpa inhibits the fast-conducting compound action potential (cap). estrogen receptors found in the plasma membrane of the sciatic nerve are affected by the bpa and inhibit cap. however, estrogen receptors are not the only reason for inhibition, bpa is able to inhibit nerve functions without affecting estrogen. a study in mice shows that bpa as an edc acts as an agonist/antagonist for behavioral effects. bpa caused a decrease in exploratory and spatial behaviors in male mice who were exposed in the developmental state. in order to expose the males, pregnant females were fed with bpa in food the mice were compared to males whose mothers were fed with a phytoestrogen-free ctl diet. males with the bpa exposure in developmental stages were less likely to be territorial when the other male mice were present. bpa exposure changed the behavior of sex and species-dependent behavior. these conclusions are suggestions to support the idea that bpa can cause sexually selected traits. furthermore, maternal diet and exposing the developmental mice to bpa, may cause harm and lead to sexually dimorphic responses. positions of national and international bodies world health organization in november 2009, the who announced to organize an expert consultation in 2010 to assess low-dose bpa exposure health effects, focusing on the nervous and behavioral system and exposure to young children. the 2010 who expert panel recommended no new regulations limiting or banning the use of bisphenol-a, stating that "initiation of public health measures would be premature." united states in 2013, the fda posted on its web site: "is bpa safe? yes. based on fda's ongoing safety review of scientific evidence, the available information continues to support the safety of bpa for the approved uses in food containers and packaging. people are exposed to low levels of bpa because, like many packaging components, very small amounts of bpa may migrate from the food packaging into foods or beverages." fda issued a statement on the basis of three previous reviews by a group of assembled agency experts in 2014 in its "final report for the review of literature and data on bpa" that said in part, "the results of these new toxicity data and studies do not affect the dose-effect level and the existing noael (5 mg/kg bw/day; oral exposure)." australia and new zealand in 2009 the australia and new zealand food safety authority (food standards australia new zealand) did not see any health risk with bisphenol a baby bottles if the manufacturer's instructions were followed, as levels of exposure were very low and would not pose a significant health risk. it added that "the move by overseas manufacturers to stop using bpa in baby bottles is a voluntary action and not the result of a specific action by regulators." in 2008 it had suggested the use of glass baby bottles if parents had concerns. in 2012 the australian government introduced a voluntary phase out of bpa use in polycarbonate baby bottles. canada in april 2008, health canada concluded that, while adverse health effects were not expected, the margin of safety was too small for formula-fed infants and proposed classifying the chemical as "'toxic' to human health and the environment." the canadian minister of health announced canada's intent to ban the import, sale, and advertisement of polycarbonate baby bottles containing bisphenol a due to safety concerns, and investigate ways to reduce bpa contamination of baby formula packaged in metal cans. subsequent news reports from april 2008 showed many retailers removing polycarbonate drinking products from their shelves. on 18 october 2008, health canada noted that "bisphenol a exposure to newborns and infants is below levels that cause effects" and that the "general public need not be concerned". in 2010, canada's department of the environment declared bpa to be a "toxic substance" and added it to schedule 1 of the canadian environmental protection act, 1999. european union the 2008 european union risk assessment report on bisphenol a, published by the european commission and european food safety authority (efsa), concluded that bisphenol a-based products, such as polycarbonate plastic and epoxy resins, are safe for consumers and the environment when used as intended. by october 2008, after the lang study was published, the efsa issued a statement concluding that the study provided no grounds to revise the current tolerable daily intake (tdi) level for bpa of 0.05 mg/kg bodyweight. on 22 december 2009, the eu environment ministers released a statement expressing concerns over recent studies showing adverse effects of exposure to endocrine disruptors. in september 2010, the european food safety authority (efsa) concluded after a "comprehensive evaluation of recent