these studies are also mixed in their findings regarding the persistence of chemicals such as triclosan, triclocarban, and other pharmaceuticals. the impact of this persistence in soils is unknown, but the link to human and land animal health is likely tied to the capacity for plants to absorb and accumulate these chemicals in their consumed tissues. studies of this kind are in early stages, but evidence of root uptake and translocation to leaves did occur for both triclosan and triclocarban in soybeans. this effect was not present in corn when tested in a different study. a cautionary approach to land application of biosolids has been advocated by some for regions where soils have lower capacities for toxics absorption or due to the presence of unknowns in sewage biosolids. in 2007 the northeast regional multi-state research committee (nec 1001) issued conservative guidelines tailored to the soils and conditions typical of the northeastern us. use of sewage sludge is prohibited for produce to be labeled usda-certified organic. in 2014 the united states grocery chain whole foods banned produce grown in sewage sludge. treated sewage sludge has been used in the uk, europe and china agriculturally for more than 80 years, though there is increasing pressure in some countries to stop the practice of land application due to farm land contamination and negative public opinion. in the 1990s there was pressure in some european countries to ban the use of sewage sludge as a fertilizer. switzerland, sweden, austria, and others introduced a ban. since the 1960s there has been cooperative activity with industry to reduce the inputs of persistent substances from factories. this has been very successful and, for example, the content of cadmium in sewage sludge in major european cities is now only 1% of what it was in 1970. incineration sludge can also be incinerated in sludge incineration plants which comes with its own set of environmental concerns (air pollution, disposal of the ash). pyrolysis of the sludge to create syngas and potentially biochar is possible, as is combustion of biofuel produced from drying sewage sludge or incineration in a waste-to-energy facility for direct production of electricity and steam for district heating or industrial uses. thermal processes can greatly reduce the volume of the sludge, as well as achieve remediation of all or some of the biological concerns. direct waste-to-energy incineration and complete combustion systems (such as the gate 5 energy system) will require multi-step cleaning of the exhaust gas, to ensure no hazardous substances are released. in addition, the ash produced by incineration or incomplete combustion processes (such as fluidized-bed dryers) may be difficult to use without subsequent treatment due to high heavy metal content; solutions to this include leaching of the ashes to remove heavy metals or in the case of ash produced in a complete-combustion process, or with biochar produced from a pyrolytic process, the heavy metals may be fixed in place and the ash material readily usable as a leeds preferred additive to concrete or asphalt. examples of other ways to use dried sewage sludge as an energy resource include the gate 5 energy system, an innovative process to power a steam turbine using heat from burning milled and dried sewage sludge, or combining dried sewage sludge with coal in coal-fired power stations. in both cases this allows for production of electricity with less carbon-dioxide emissions than conventional coal-fired power stations. health risks in 2011, the epa commissioned a study at the united states national research council (nrc) to determine the health risks of sludge. in this document the nrc pointed out that many of the dangers of sludge are unknown and unassessed. the nrc published "biosolids applied to land: advancing standards and practices" in july 2002. the nrc concluded that while there is no documented scientific evidence that sewage sludge regulations have failed to protect public health, there is persistent uncertainty on possible adverse health effects. the nrc noted that further research is needed and made about 60 recommendations for addressing public health concerns, scientific uncertainties, and data gaps in the science underlying the sewage sludge standards. the epa responded with a commitment to conduct research addressing the nrc recommendations. residents living near class b sludge processing sites may experience asthma or pulmonary distress due to bioaerosols released from sludge fields. a 2004 survey of 48 individuals near affected sites found that most reported irritation symptoms, about half reported an infection within a month of the application, and about a fourth were affected by staphylococcus aureus, including two deaths. the number of reported s. aureus infections was 25 times as high as in hospitalized patients, a high-risk group. the authors point out that regulations call for protective gear when handling class b biosolids and that similar protections could be considered for residents in nearby areas given the wind conditions. in 2007, a health survey of persons living in close proximity to class b sludged land was conducted. a sample of 437 people exposed to class b sludge (living within 1-mile (1.6 km) of sludged land) - and using a control group of 176 people not exposed to sludge (not living within 1-mile (1.6 km) of sludged land) reported the following: "results revealed that some reported health-related symptoms were statistically significantly elevated among the exposed residents, including excessive secretion of tears, abdominal bloating, jaundice, skin ulcer, dehydration, weight loss, and general weakness. the frequency of reported occurrence of bronchitis, upper respiratory infection, and giardiasis were also statistically significantly elevated. the findings suggest an increased risk for certain respiratory, gastrointestinal, and other diseases among residents living near farm fields on which the use of biosolids was permitted."— khuder, et al., health survey of residents living near farm fields permitted to receive biosolids although correlation does not imply causation, such extensive correlations may lead reasonable people to conclude that precaution is necessary in dealing with sludge and sludged farmlands. harrison and oakes suggest that, in particular, "until investigations are carried out that answer these questions (...about the safety of class b sludge...), land application of class b sludges should be viewed as a practice that subjects neighbors and workers to substantial risk of disease." they further suggest that even class a treated sludge may have chemical contaminants (including heavy metals, such as lead) or endotoxins present, and a precautionary approach may be justified on this basis, though the vast majority of incidents reported by lewis, et al. have been correlated with exposure to class b untreated sludge and not class a treated sludge. a 2005 report by the state of north carolina concluded that "a surveillance program of humans living near application sites should be developed to determine if there are adverse health effects in humans and animals as a result of biosolids application." the chain of sewage sledge to biosolids to fertilizers has resulted in pfass ("forever chemicals") contamination of farm produce in maine in 2021 and beef raised in michigan in 2022. the epa pfas strategic roadmap initiative, running from 2021 to 2024, will consider the full lifecycle of pfas including health risks of pfas in wastewater sludge. regulation and guidelines european union european legislation on dangerous substances has eliminated the production and marketing of some substances that have been of historic concern such as persistent organic micro-pollutants. the european commission has said repeatedly that the "directive on the protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture" (86/278/eec) has been very successful in that there have been no cases of adverse effect where it has been applied. the ec encourages the use of sewage sludge in agriculture because it conserves organic matter and completes nutrient cycles. recycling of phosphate is regarded as especially important because the phosphate industry predicts that at the current rate of extraction the economic reserves will be exhausted in 100 or at most 250 years. phosphate can be recovered with minimal capital expenditure as technology currently exists, but municipalities have little political will to attempt nutrient extraction, instead opting for a "take all the other stuff" mentality. european countries that joined the eu after 2004 favor landfills as a means of disposal for sewage sludge. in 2006, the predicted sewage sludge growth rate was 10 million tons of sewage sludge per year. this increase in the amount of sewage sludge accumulation in the eu can be due to the increase in the number of households that are connected to the sewage system. the eu has directives in place to encourage the use of sewage sludge in agriculture, in a way that will not harm the soil, humans, and the environment are not harmed. a guideline the eu has put into place it that sewage sludge should not be added to fruit and vegetable crops that are in season. in austria, in order to dispose of the sewage sludge in a landfill, it must first be treated in a way that reduces its biological reactivity. sweden no longer allows sewage sludge to be disposed in the land fills. in the eu, regulations regarding sewage sludge disposal differ because legislation regarding landfill disposal in not in the national regulations for the eu. united states according to the epa, biosolids that meet treatment and pollutant content criteria of part 503.13 "can be safely recycled and applied as fertilizer to sustainably improve and maintain productive soils and stimulate plant growth." however, they can not be disposed of in a sludge only landfill under part 503.23 because of high chromium levels and boundary restrictions. biosolids that meet the class b pathogen treatment and pollutant criteria, in accordance with the epa "standards for the use or disposal of sewage sludge" (40 cfr part 503), can be land applied with formal site restrictions and strict record keeping. biosolids that meet class a pathogen reduction requirements or equivalent treatment by a "process to further reduce pathogens" (pfrp) have the least restrictions on use. pfrps include pasteurization, heat drying, thermophilic composting (aerobic digestion, most common method), and beta or gamma ray irradiation. the epa office of the inspector general (oig) completed two assessments in 2000 and 2002 of the epa sewage sludge program. the follow-up report in 2002 documented that "the epa cannot assure the public that current land application practices are protective of human health and the environment." the report also documented that there had been an almost 100% reduction in epa enforcement resources since the earlier assessment. this is probably the greatest issue with the practice: under both the federal program operated by the epa and those of the several states, there is limited inspection and oversight by agencies charged with regulating these practices. to some degree, this lack of oversight is a function of the perceived (by the regulatory agencies) benign nature of the practice. however, a greater underlying issue is funding. few states and the us epa have the discretionary funds necessary to establish and implement a full enforcement program for biosolids. as detailed in the 1995 plain english guide to the part 503 risk assessment, the epa's most comprehensive risk assessment was completed for biosolids. prior to 1991 since 1884 when sewage was first treated the amount of sludge has increased along with population and more advanced treatment technology (secondary treatment in addition to primary treatment). in the case of new york city, at first the sludge was discharged directly along the banks of rivers surrounding the city, then later piped further into the rivers, and then further still out into the harbor. in 1924, to relieve a dismal condition in new york harbor, new york city began dumping sludge at sea at a location in the new york bight called the 12-mile site. this was deemed a successful public health measure and not until the late 1960s was there any examination of its consequences to marine life or to humans. there was accumulation of sludge particles on the seafloor and consequent changes in the numbers and types of benthic organisms. in 1970 a large area around the site was closed to shellfishing. from then until 1986, the practice of dumping at the 12-mile site came under increasing pressure stemming from a series of untoward environmental crises in the new york bight that were attributed partly to sludge dumping. in 1986, sludge dumping was moved still