EPA revs up to regulate biotechnology.
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DNA, Recombinant↗
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Regulating biotechnology.
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Advisory Committees↗
Design of carcinogenicity studies: a backward glance.
Despite extensive research carried out over many years, a completely satisfactory method of testing drugs and chemicals for carcinogenicity continues to elude toxicologists. In the past, numerous scientific groups, regulatory agencies, and regional bodies have discussed and published specific recommendations and guidelines regarding the testing requirements for carcinogenicity studies. The Food, Drug and Cosmetic Act became law in 1938, but it was not until after the Second World War that serious concerns regarding chemicals became prevalent. Testing guidelines were nonexistent until 1949 when the FDA published "Procedures for the Appraisal of the Toxicity of Chemicals in Foods." This key publication was the forerunner of the famous "Gray Book" (1959) in which were outlined many of the specific carcinogenicity testing procedures still used today. Guidelines and regulations became the watchwords during the 60's and 1970's. Formation of the EPA, more stringent testing requirements, Toxic Substances legislation, and Environmental Control Acts followed one another in short order. NCl's Technical Report #1 (1976) entitled, "Guidelines for Carcinogen Bioassay in Small Rodents" probably had the greatest impact of any publication on carcinogenicity testing. Many later guidelines and recommendations were based on this publication.
Animals↗
From health-based to technology-based standards for hazardous air pollutants.
The Clean Air Act Amendments of 1990 represent a major shift in regulatory emphasis for toxic air pollutants. Recognizing the immediate public health benefits that can be gained from the application of currently available and affordable control technologies, Congress has abandoned its insistence that health risks should be the only consideration in establishing emissions standards. Previously excluded concerns about economic costs and technological feasibility will now determine the initial level of pollution control required of toxic air pollution sources. In exchange for reducing the stringency of emissions limits, the newly amended act extends the scope of regulation by listing 189 toxic substances that must be controlled over the next decade. This exchange of regulatory depth for breadth occurs against a history of reluctance by the Environmental Protection Agency to implement the original health-protective language of the Clean Air Act. It mirrors earlier compromises under the Clean Water Act and the Occupational Safety and Health Act.
Air Pollutants↗
Assessing the health risks of priority substances under the Canadian environmental protection act.
The Canadian Environmental Protection Act (CEPA) came into force in June 1988. This legislation provides the federal government with broad powers to deal with health and environmental problems posed by chemicals and the products of biotechnology throughout their life cycle. Responsibility for administering CEPA is shared between the Department of the Environment and the Department of National Health and Welfare. Part II of the Act, the "toxic substances" provisions, enables the federal government to impose controls on substances new to Canadian commerce and to address the health and environmental risks posed by existing substances. Part II of CEPA also delineates the manner in which existing substances are to be selected for assessment (priority substances) and controlled. The first Priority Substances List was published in February 1989. The 44 entries on this list include discrete chemicals, classes of chemicals, and complex mixtures of chemicals; the Department of the Environment and the Department of National Health and Welfare must ascertain whether these substances pose a risk (are "toxic" as defined in CEPA) to the environment or to human health by February 1994. This paper outlines the administrative arrangements for conducting risk assessments and the requirements for ascertaining whether a substance is "toxic" with respect to human health under CEPA. The rationale for deeming dioxins and furans, the first two priority substances to be assessed, as "toxic" with respect to human health is also described.
Canada↗
An introduction to a UK scheme to help small firms control health risks from chemicals.
The Control of Substances Hazardous to Health Regulations 1994 (COSHH), provide the main British legislation to protect against health risks arising from hazardous substances used at work. Under the regulations, employers have a duty to carry out a suitable and sufficient risk assessment and take steps to ensure exposure is adequately controlled. The paper by Topping et al. (1998) concluded that small firms need more basic, readily available advice on how to effectively control hazardous substances. To meet this need the Health and Safety Executive (HSE) and the Advisory Committee on Toxic Substances (ACTS) have developed a new scheme for the UK. It involves a simple system of generic risk assessments to identify appropriate control strategies and a series of control guidance sheets providing good-practice examples of those strategies for common operations. The approach builds on earlier industry risk banding schemes and HSE's general approach to risk assessment and risk management. To help ensure the advice reaches small firms, HSE is seeking to involve key intermediaries in its dissemination. This paper describes the rationale for the new UK scheme, how it sits in the legal framework, and proposals for its dissemination. The papers by Brooke (1998) and Maidment (1998) set out in detail the technical basis for the scheme.
Air Pollutants, Occupational↗
Toxin-producing plankton may act as a biological control for planktonic blooms--field study and mathematical modelling.
Termination of planktonic blooms is of great importance to human health, ecosystem, environment, tourism and fisheries. Toxic substances released by plankton play an important role in this context. The effect of toxin-producing plankton (TPP) on zooplankton is observed from the field-collected samples and mathematical modelling. Information from both the studies led us to suggest that TPP may terminate the planktonic blooms by decreasing the grazing pressure of zooplankton and thus acts as a biological control.
Animals↗
Interaction of public policy advocacy and research in the passage of New Zealand's Smoke-free Environments Act 1990.
This paper examines the public policy campaign that led up to the passage of New Zealand's Smoke-free Environment Act 1990, arguably the toughest tobacco control legislation in the world, focusing on the critical interaction between advocacy and research. The paper argues that had it not been for the Toxic Substances Board Report and the publicity it received, it is doubtful that the Smoke-free Environments Act would have been enacted. The tobacco industry catch cry that ad bans don't work, largely fell on deaf ears because of the Toxic Substances Board Report's findings, and the public health advocate's ability to refer to an authoritative Department of Health document.
Air Pollution↗
Examining the debate on the use of medical marijuana.
The opium poppy and the coca leaf offer useful perspectives on the current controversies over medical marijuana. In both cases, purified synthetic analogues of biologically active components of ancient folk remedies have become medical mainstays without undermining efforts to reduce nonmedical drug use. A decade ago, a campaign strove to legalize heroin for the compassionate treatment of pain in terminally ill patients. Like the current campaign to legalize medical marijuana, many well-meaning people supported this effort. The campaign for medical heroin was stopped by science when double-blind studies showed that heroin offered no benefits over the standard opioid analgesics in the treatment of severe cancer pain. Scientific medicine requires purified chemicals in carefully controlled doses without contaminating toxic substances. That a doctor would one day write a prescription for leaves to be burned is unimaginable. The Controlled Substances Act and international treaties limit the use of abused drugs or medicines. In contrast to smoked marijuana, specific chemicals in marijuana or, more likely, synthetic analogues, may prove to be of benefit to some patients with specific illnesses. Most opponents of medical use of smoked marijuana are not hostile to the medical use of purified synthetic analogues or even synthetic tetrahydrocannabinol (THC), which has been available in the United States for prescription by any licensed doctor since 1985. In contrast, most supporters of smoked marijuana are hostile to the use of purified chemicals from marijuana, insisting that only smoked marijuana leaves be used as "medicine," revealing clearly that their motivation is not scientific medicine but the back door legalization of marijuana.
Cannabis↗
Occupational exposure limits for chemicals.
Occupational exposure limits (OELs) are tools to help employers protect the health of those who may be exposed to chemicals in their workplace. Under the United Kingdom Control of Substances Hazardous to Health (COSHH) Regulations they define adequate control by inhalation. OELs are set by the Health and Safety Commission (HSC) on advice from its Advisory Committee on Toxic Substances (ACTS) and after public consultation. Thus they are consensus limits which have the support of both sides of industry. COSHH uses two types of occupational exposure limit-the occupational exposure standard (OES) and the maximum exposure limit (MEL). OESs are set for substances for which it is possible to identify a concentration at which there is no significant risk to health. Employers are required to meet the limit, there is no requirement to go below it, and it can be exceeded provided steps are taken to meet it as soon as reasonably practicable. MELs are set for substances which have serious health implications and for which an OES cannot be set. Most of the substances with MELs are either carcinogens or causes of occupational asthma. Employers must not exceed an MEL and must reduce exposure as far below it as is reasonably practicable. MELs are set at concentrations achievable by good occupational hygiene practice such that risks to workers are judged to be reduced to a tolerable level. The HSC consider that this approach is preferable to the use of mathematical models to generate risk estimates, which inevitably gives a spurious appearance of accuracy. The MEL/OES system is poorly understand by many employers who use chemicals, is not comprehensive as some substances meet neither the OES nor MEL criteria, and does not mesh well with indicative occupational exposure limit values which will increasingly be set under the European Union Chemical Agents Directive. COSHH essentials: easy steps to control chemicals provides the practical help that firms need to control chemicals. It takes users straight from hazard and exposure considerations to benchmark standards of good practice. The problems with the current system have prompted ACTS to set up a subgroup to review the OEL framework.
Chemical Industry↗
Injurious effect of Helicobacter pylori culture fluid to gastroduodenal mucosa, and its detoxification by sucralfate in the rat.
BACKGROUND: Helicobacter pylori plays an important role in the pathogenesis of peptic ulcer. Although several cytotoxins related to H. pylori have been reported, their effects on gastroduodenal mucosa have not been well evaluated in vivo. AIM: To investigate the effects of the combination of acid and toxic substances derived from H. pylori on gastroduodenal mucosa, and to observe the effect of sucralfate on such factors in the rat. METHODS: Male Sprague-Dawley rats were fasted overnight and anaesthetized. The pylorus was ligated, and a double-lumen cannula was inserted into the forestomach for gastric luminal perfusion. In other animals, a cannula was inserted to perfuse the proximal duodenum. 51Cr-EDTA was administered intravenously and mucosal integrity was monitored by measuring the blood-to-lumen 51Cr-EDTA clearance. After 72 h of culture of H. pylori (NCTC11637 and Sydney strain 1), Brucella broth containing 3% FBS was filtered to remove the bacteria (supernate of H. pylori culture fluid; HPsup). HPsup was acidified (pH=2.0) with HCl, and tested for its injurious action on gastric or duodenal mucosa by luminal perfusion. HPsup was incubated with sucralfate for 30 min. The supernate was collected by centrifugation and the pH was readjusted to 2.0. This sucralfate-treated HPsup was used to test the effect of sucralfate against H. pylori-related mucosal injurious factors. RESULTS: Non-acidified and acidified HPsup did not cause any detectable injury to the gastric mucosa. Non-acidified HPsup did not cause injury in the duodenal mucosa. However, acidified HPsup induced a significantly greater increase in 51Cr-EDTA clearance and greater histological damage than in controls. Sucralfate completely reversed this. CONCLUSION: These results suggest that an H. pylori-related toxic substance may aggravate duodenal acid injury by acting on luminal surfaces, and that the detoxification of this substance by sucralfate may contribute to its anti-ulcer action.
Animals↗
A massive outbreak of food poisoning--a reminder of the importance of proper toxic waste control.
Because of rapid urbanisation in South Africa, scavenging from waste disposal sites by poor communities poses an increasing health risk. Reject cough lozenges, some of which contained larger amounts of dextromethorphan than usual, were illegally removed from a disposal site and, after resale by informal traders, caused moderately severe symptoms of toxicity in 171/540 (24%) primary school pupils. Although dextromethorphan was implicated as a cause, contributing effects of other toxins could not be excluded. Bacteriological cultures and a pesticide screen were negative. Had more toxic substances been involved, the consequences would have been disastrous. This incident supports calls for an integrated national waste management policy and waste control act to govern the management and control of waste from generation to disposal. Such a policy is necessary to prevent potentially serious incidents in the future.
Antitussive Agents↗
Taste recognition: food for thought.
The ability to identify food that is nutrient-rich and avoid toxic substances is essential for an animal's survival. Although olfaction and vision contribute to food detection, the gustatory system acts as a final checkpoint control for food acceptance or rejection behavior. Recent studies with model organisms such as mice and Drosophila have identified candidate taste receptors and examined the logic of taste coding in the periphery. Despite differences in terms of gustatory anatomy and taste-receptor families, these gustatory systems share a basic organization that is different from other sensory systems. This review will summarize our current understanding of taste recognition in mammals and Drosophila, highlighting similarities and raising several as yet unanswered questions.
Animals↗
Commentary: two seminal contributions of S. A. Roach to the evaluation and control of hazardous substances in air.
S. A. Roach was a pioneer in the assessment and control of hazardous substances in the working environment during the second half of the 20th century. The two papers discussed in this commentary are generally regarded as his most important scientific contributions. The first paper (Roach, 1977) dealt with the determinants of the body burdens of toxic air contaminants. Using simple kinetic models, he showed how levels of toxicants rise and fall in the body according to the patterns of airborne exposures received during relevant time windows. This led to several useful rules of thumb, including the timing of grab samples for 'fast acting' substances, the appropriate duration of air samples relative to the biological half time, how to deal with unusual work schedules, and how to integrate exposure assessment with control. He also offered sage advice regarding the meaning and interpretation of exposure limits, the importance of repeated monitoring, and the extent to which unacceptable levels of exposure might be reduced. In concluding this work, Roach emphasized that the hygienist can fulfill a central role in occupational health simply by intervening to reduce the body burden. The second paper (Roach, 1981) dealt with the design of effective ventilation systems to control worker exposure to toxic airborne contaminants. By developing a series of simple differential equations, Roach evaluated the impact of turbulent diffusion upon industrial ventilation. He emphasized that the stationary contaminant concentration was proportional to the contaminant generation rate and that velocity alone was not a sufficient design criterion to control exposures. Rather, he argued that the equivalent ventilation rate (the ratio of the contaminant generation rate to the steady concentration in the breathing zone) should be the guiding criterion for ventilation design. Throughout both papers, Roach used fundamental principles to tie together exposure assessment and engineering control, and pointed the way to a science for occupational hygiene. The profession can still learn a great deal from these seminal contributions.
Air Pollutants, Occupational↗
Implications of health and safety legislation.
The UK Health and Safety at Work Act is described; the duties of the employer, including manufacturers, importers and suppliers, and of the employee for health and safety are laid down. This Act provides the necessary legislative framework for the control of carcinogenic, mutagenic and other health hazards at work. Proposed regulations dealing specifically with carcinogenic substances and with the notification of toxic properties will add strength to these general provisions. The implementation of the new regulations will be the responsibility of the Health and Safety Commission, advised by an expert subcommittee. Ad hoc decisions about handling known and suspected carcinogens are made in consultation with employers and employees. For practical purposes, there must be working limits for carcinogens; zero levels and 'lowest levels of detection' are impracticable. The difficulties of defining the criteria by which substances are judged to be carcinogenic to humans are outlined. Science plays only one part in decision-making, and final decisions depend also on social and economic needs.
Carcinogens, Environmental↗
A randomized controlled trial of acarbose in hepatic encephalopathy.
BACKGROUND & AIMS: Hepatic encephalopathy in cirrhosis is contributed to by toxic products deriving from the proteolytic bacterial flora-related degradation of dietary nitrogen substances. Acarbose is a novel hypoglycemic agent acting through the inhibition of glucose absorption in the gut and the promotion of intestinal saccharolytic bacterial flora at the expense of proteolytic flora. We assessed whether acarbose exerts a beneficial effect on hepatic encephalopathy and on postprandial hyperglycemia in cirrhotic patients with low-grade hepatic encephalopathy and type 2 diabetes mellitus. METHODS: One hundred seven cirrhotic patients with grade 1-2 hepatic encephalopathy and type 2 diabetes mellitus were randomized to acarbose 100 mg 3 times daily or placebo for 8 weeks; after a 2-week washout period, treatments were switched, and patients were followed for 8 more weeks. Ammonia blood levels, Reitan's number connection test, intellectual function, fasting and postprandial glucose levels, glycated hemoglobin values, and C peptide values were determined 2 weeks before and 4, 8, 11, 14, and 18 weeks after treatment. RESULTS: (1) Acarbose significantly decreased ammonia blood levels and improved Reitan's test score and intellectual function score compared with placebo (P < .01). (2) Acarbose caused a 33% decrease in fasting glucose level and an approximately 50% decrease in postprandial glucose level compared with placebo (P < .01). (3) Acarbose significantly lowered glycated hemoglobin values and postprandial C peptide compared with baseline values, whereas placebo did not. (4) No change in biochemical parameters of liver function was observed after acarbose treatment. CONCLUSIONS: Acarbose is a safe and effective drug in cirrhotic patients with low-grade hepatic encephalopathy and type 2 diabetes mellitus.
Acarbose↗
Lamotrigine in Parkinson's disease--a double blind study.
Antiglutamatergic acting substances are considered to be useful tools for the treatment of hypokinesia in animal models for Parkinson's disease (PD). Moreover, most known antiglutamatergic compounds act postsynaptically and are either toxic or weak with regard to their clinical potency. The antiepileptic drug "Lamotrigine (LTG)" inhibits presynaptic glutamate release and may therefore provide a novel approach for PD therapy. Encouraging results from a pilot project led us to establish a placebo controlled trial including 20 patients with PD. The substance was generally well tolerated. There was a significant difference in the investigator's overall assessment of efficacy (6/10 vs. 2/10 improvement; p < 0.05) and a tendency for LTG to exhibit a beneficial effect in some registration parameters, but no significant differences in motor response were found between the two groups. We failed to confirm that LTG mediates a strong antiparkinsonian effect in this small study, but to clearly demonstrate slight or moderate beneficial effects larger groups are required.
Adult↗