Dev.Chem.Eng. Mineral Process., 8(lL?),pp.3-14.2OOO. Safety and Chemicals I.A. Furzer Department of Chemical Engineering, University of Sydney, New South Wales 2006, AUSTRALL4 Chemical engineers need to be aware of the increasing concern over the sqfe use of chemicals, a duty of care, and a positive eflort to reduce exposure to chemicals by both the general public and persons working in the occupational environment. Benzene inhalation f?om gasoline during automobile tank filling should be minimized in order to reduce the risk of leukemia. Dermal absorption of pesticides and solvents can have adverse health Meets. Captan, an old pesticide about to re-appear, is examined as a potential human carcinogen. Persistent old organochlorines in meat can enter the human food chain. Organophosphate pesticih, 50 times more toxic than HCN, are detected in Australian beef and sheep samples. The best estimate of occupational mortality due to past chemical exposure is 2,300 people per year. Chemical engineers need the management vision to include safety and chemicals in the design and operation of plant, and in the pathways leading to inhalation, ingestion and absorption in humans. Introduction The chemical engineer needs to be aware of the safety aspects of chemicals and their effect on humans. The subject is very broad and includes public, occupational and environmental health. A dramatic safety event such as a fire or explosion can result in the exposure of humans to chemicals, either by the workforce at the plant or the public, outside the plant. If these chemicals enter the 3 1.A. Furzer water or soil environment then there may be a complex pathway to exposure of humans by these chemicals in the future. There is obviously public concern over such a dramatic event and it is the responsibility of the chemical engineer to reduce the risk of exposure of humans to chemicals in the design phase, the operation of the plant and during the life cycle of the plant. Of increasing concern is the non-dramatic event, the small release of chemicals over a long period of time, which results in occupational exposure to a hazardous substance. This exposure may produce an adverse health effect, such as cancer, 10 or 20 years after the chemical exposure. The public would be subjected to lower levels of exposure, but it may operate for 24 hours a day, for 7 days a week. Safe levels of exposure of the public to chemicals may be several orders of magnitude less, than the 8 hour, 5 day week, occupational health exposure limit. One such chemical is benzene, which has been extensively investigated (l), and the epidemiological evidence is that it is causually linked to leukaemia. Benzene is widely used as a raw material in the petrochemical industry, in pesticide and herbicide plants and in gasoline. Gasoline disbibution to the pump outlet, leads to the potential for public exposure to benzene, through inhalation and skin absorption. Safety with benzene, must start with chemical engineers being aware of the toxic nature of benzene, and the identified risk to human health through cancers. The policy to be followed by chemical engineers is to investigate alternative or substitute chemicals with a lower adverse health risk to humans. In some cases, benzene is a key component in the process chain for the production of polymers, resins or plastics. Would the chemical engineer have to look further than benzene, and ask the question, “Should we change the polymer, resin or plastic?” to reduce the exposure to the toxic substance benzene. This would be a major change to the market and could only be introduced due to public concern and the political will,and if a company has made a research and development breakthrough. It would meet with considerable economic opposition as there are present investments in conventional plant. The standard alternative, is to pay special attention to containment, to prevent the exposure of benzene to humans. This can be done provided the risk of fire, explosion and plant failure is 4 Safety and Chemicals adequately taken into account. However a prevention of exposure policy to benzene at the tank filling operation for the public would be an expensive exercise. There are of course many other hazardous substances that are more toxic than benzene in a chemical plant, and they need to be safely contained. The chemical engineer needs to think about the long pathway between using his or her skills in producing a chemical, to the inhalation, ingestion and absorption of that chemical by humans and an adverse health effect which may appear soon after exposure, or in the case of cancers, several decades later. Skin Absorption and Sensitivity to Chemicals There is a distribution of sensitivity to chemicals by the general population, which leads to a dismiution of risk of an adverse health effect to humans. The adverse health effect may be a sensitive skin effect to the chemical or skin absorption, leading to exposure to the chemical. These adverse health effects are well described (2) and include the dermal absorption of certain pesticides that can readily penetrate the intact skin and pose a far greater danger than exposure by inhalation. It should be noted the Australian national occupational exposure standard is for inhalation, only. Chemicals requiring special precautions to prevent absorption through the skin include captan, carbon tetrachloride and mevinphos. Table 1 contains a brief list of some chemicals that can cause an adverse health effect through skin absorption and chemical sensitivity. Table 1. Special Precautions Requiredfor the Following chemicals: Skin absorption and chemical sensitiviw. Acrylonitrile Aldrin 4-Aminodiphenyl Aniline Azinphos-methyl Benzidine captafol Captan Carbon tetrachloride Chlordane Cresol Cumene Cyanides Dieldrin Fenamiphos Isocyanates Mevinphos Nicotine Polychlorinated Benzenes TNT 5 14. Furzer Other effects of chemicals on the skin include solvents which can degrease the slan, and corrosive substances that can cause serious injuries to the eyes and skin. Certain drugs and dyes coming into contact with the skin and in the presence of selected wavelengths of light can cause dermatitis and other health effects. It is good practice to avoid any unnecessary contact with all chemical substances. Some chemicals such as formaldehyde can cause a specific immune response, which is termed, sensitisation. This may produce an extremely severe reaction including an asthmatic condition. Once the sensitised state has been produced, an affected person may react to chemical exposure of that substance, at minute levels of exposure. The ~ t i 0 occupational ~ 1 exposure standard states that the recommended exposure standard for strong semitising agents may not provide adequate protection for a hypersensitive person. The chemical engineer needs to be aware of skin absorption and sensitivity to chemicals of the general public as well as workers in the occupational environment. The distribution of sensitivity in the general public would include the following groups; the pregnant woman, the foetus, infants, children, the elderly and people with weakened immune systems. The question arises, “What public exposure standzuds to chemicals need to be made?” All of the above groups definitely need special attention, and a considerable lower exposure to chemicals than the healthy adult. One of the present methods of achieving this,is to introduce a safety factor, like 100 and reduce the public exposure to a chemical by a factor of 100. However is it adequate for the developing cells in the foetus and the hypersensitive person? This safety factor may need to be substantially increased to cover 95% of the sensitivity effects of chemicals on the general public. Good practice for the public must be to minimize all unnecessary contact with chemicals. Multiple chemical sensitivity (MCS) is a controversial reaction to twentieth century chemicals, that may ox may not exist. How is the chemical engineer to come to terms with members of the general public claiming severe reactions to chemicals? If MCS exists, then should the safety factor be increased beyond 95% of the general public to include the hypersensitive person? The US Department of 6 Safery and Chemicals Health and Human Services has an internet site (health.gov) with a database that lists 11,000 references to MCS. With this extensive activity from the environmental, medical, chemical and engineering groups on MCS, then chemical engineers need vision to plan now for any legislation on MCS. Some members of the public (3) have described the situation for the hypersensitive as a chemical crisis. Active Constituent in the Fungicide: Captan Captan, has the IUPAC chemical name: N-[(trichloromethyl)thio]cyclohex-4-ene- 1,2-dicarboximide7C9H& 13N02S. Captan was withdrawn in 1986 for use in the agricultural area, due to its high toxicity. In July 1997, a Public Release Summary (4) was provided to consider the release of a fungicide containing 80% captan as the active ingredient. The summary document appears to be an extensive covering of the following aspects; agricultural, environmental, public health and safety, residue in food, trade and occupational health and safety. The captan containing fungicide is proposed for use to control the black spot on apples and pears, grey mould on grapes, brown rot on stone h i t , blight on strawberries and brown patch on turf. Surprisingly captan-containing products are registered in 28 countries, including the USA, Germany, Denmark and Uruguay. The arguments put forward for the re-introduction of captan-containing fungicide in Australia are the demand for a broad-spectrum fungicide, and improved knowledge which may contradict conclusions reached earlier. The risk assessments to human health are based on dose levels at the no observable effect level (NOEL), and this leads to acceptable limits for dietary or other intakes at which no adverse health effects in humans could be expected. While this NOEL concept is widely used, it should be considered in conjunction with the distribution of chemical sensitivity in the general public. Should the NOEL levels be reduced for the hypersensitive person? The summary includes information on toxicokinetics, metabolism, acute studies, short-term studies, long term studies, reproduction and developmental 7 I.A. Furrer studies, genotoxicity and other studies. Over a period of several decades, exhaustive studies have been made of the genotoxicity of captan to human cells in vitro (test tube studies). Captan is clearly DNA reactive and genotoxic in vitro to human cells. There is now conflicting evidence for the induction of bone marrow chromosomal aberrations in vivo (in living organisms), This new evidence is the basis for the proposed introduction of captan into agriculture in Australia. The rabbit was studied for the effect of captan and is the basis at arriving at the NOEL value and the acceptable daily intake (ADI)for humans. There are of course uncertainties in extrapolating results from rabbits to humans. There are other uncertainties concerned with the distribution of chemical sensitivities in the general public, and how adequately the chemically hypersensitive are accounted for. However the most important uncertainty is the proper evaluation of the potential hazard to humans. The summary establishes a safety factor of 100 for captan for humans. The chemical engineer should take a fresh look at this safety factor and the qualitative basis at arriving at this result. It may be necessary to include a qualitative approach to captan at the present time, but is the safety factor of 100, adequate? The Australian occupational exposure standard for captan (3), expressed as the 8 hour TWA is 0.5 mg/m3 and is a probable human carcinogen; category 2. This category is based on the sufficient evidence concept, to provide a strong presumption that human exposure might result in the development of cancer. Captan should be treated as if it was carcinogenic to humans. The chemical engineer could be well advised to leave captan alone, as its potential for human cancer development is too high. The United States, Occupational Safety and Health Administration has the internet site (osha.gov) and captan has a TWA of 5 mg/m3 and is potentially carcinogenic to humans. The economic potential of producing a perfect bunch of grapes and the sale in the market place is high. However if the public was aware that captan was sprayed on grapes, strawberries, stone h i t and on turf, there could well be an adverse market reaction. A recommendation of a maximum residue limit (MRL) in foods, such as grapes, of 10 m a g and a temporary limit of 25 m a g in 8 Safety and Chemicals strawberries is of concern when captan is a category 2, carcinogen. The use of captan on turf is disturbing as it has the potential to place captan around the domestic house, leading to a high risk of human exposure, particularly to children. Five repeat applications of captan are recommended in keeping with resistance management guidelines for turf. The product label on this fungicide containing captan, includes a re-entry instruction to the sprayed site. For apples and pears; no re-entry is permitted for 7 days. For chemical engineers engaged in blending and packaging the plant must have an air extraction system, and workers are to wear personal protective clothmg. The occupational exposure of the end user, the farmer to captan would be by skin absorption. Would the farmer follow the product safety directions of avoiding skin contact and not to inhale dust or spray? The end users are also required to wear cotton overalls, a hat, PVC gloves and goggles. Would the Australian farmer really use this captan containing fungicide, follow these elaborate instructions and risk exposure to a potential human carcinogen? Has the premise that the labelling instructions will be followed, gone too far? Spraying of fungicide is not very efficient, with spray drift delivering a potential human carcinogen over the boundary fence to the public. This spray drift is difficult to effectively control and may be associated with MCS. Revised Safe Chemicals There have been a number of important chemical developments in the past, that have resulted in chemicals with almost wonder properties. One of the most important was DDT,which was shown at the time to have a low toxicity towards humans and was an effective insecticide. The history of DDT is well established and today we know it accumulates in human fatty tissue. There are a number of other chemicals such as the fieons, which are relatively nontoxic to humans and are prohibited due to treaties on ozone. Asbestos mining and processing into insulation material and building products was another wonder inert material that is now known to cause cancer in humans. Carbon dioxide and 6 other chemicals are known as the greenhouse gases and the recent Kyoto summit has set target 9 I.A. Furzer reductions in emissions of these gases to control global warming and reduce adverse health effects on humans. Chemical engineers need to note that chemicals may be relatively safe by today's standard, may be prohibited in the future due to improved knowledge on adverse health effects on humans. Considerable planning skills are needed by managers to anticipate these future changes and the effects on chemicals production and profitability. The World Health Organizaton has established an international body, the Codex Alimentarium Commission, to develop international standards to protect humans from chemical residues in food. The MRL values are acceptable limits of pesticide and veterinary drug residues in food, and listed by the Codex Alimentarium. The Australian Bureau of Resource Sciences has published the National Residues Survey (5) to monitor chemical residues in food. The main factors in considering the risk to humans are, perceptions in the international and domestic market and possible public health hazards. 30 25 20 I 1 15 10 5 0 1984 1986 1988 1990 1992 1994 1996 Year Figure 1. Organochlorinesdetected in samples. 10 Safety and Chemicals About 50,000 analyses are conducted each year on a meat program containing beef, sheep and other meats, a grain program containing wheat, barley flour etc and a smaller horticulture program. Figure 1 shows the detection of organochlorines, such as aldnn, dieldrin, BHC, chlordane, DDT, DDD, DDE HCD, heptachlor, lindane and other chlorine containing chemicals. It is astonishing that about 20% of all beef and sheep samples in Australia contained organochlorines, 15 years ago. The persistence of organochlorines in the soil is well established by the very slow reduction in these chemicals in beef and sheep samples as shown by Figure 1. In 1996, about 3 4 % of all samples contained organochlorines,but only 1 sample exceeded the MRL value. Soil remediation to remove organochlorines in Australian pastures would be an expensive exercise. Prevention would have been a better policy. Could we leam from this mistake, in considering agricultural programs from the natural predator viewpoine or a smart chemical, that poses no adverse health effect to humans. Organophosphates have also been detected in beef and sheep samples. About 3,000 analyses were conducted in 1996 and organophosphates detected in 15 cases. No samples exceeded the MRL for organophosphates. The organophosphates detected were diazinon, ethion, fenthion and chlorpyriphos. The exposure standard (3) contains the 8 hour TWA (time weighted average) value for these 4 organophosphates, see Table 2. Table 2. W A 8-hour values. Organophosphatesdetected in beef and sheep samples. Chemical mgh3 Diazinon 0.1 Ethion 0.4 Fenthion 0.2 Chlorpyriphos 0.2 11 I.A. Furzer From the chemical engineers point of view, these are grouped in the most toxic category of occupational chemicals, see (6). Special precautions are needed in the operation of plant, blending and packaging of these 4 organophosphates. The standard gives an 8-hour TWA for hydrogen cyanide of 11 mg/m3; so these 4 organophosphates are about 50 times more toxic than hydrogen cyanide. There must be some concern that such toxic chemicals can be detected in beef and sheep samples, even though the compositions are below MRL values. Is this a case where MRL values for organophosphates could be lowered in the future, to prevent the intake in food. What effect are these small compositions having on the weakened groups in the distribution of sensitivities in the general public? Should chemical engineers be looking at smarter ways to replace these organophosphates that can enter the human food chain? Should this sampling program be expanded to cover a wider risk fraction of the domestic market in Australia? If public awareness of these matters is high then there is a likelihood of changes in this pesticide market, leading to a reduction in the adverse health effect on humans. Best Estimate of the Adverse Health Effect It is difficult to collect hard epidemiological evidence between a human group that has been exposed to a chemical and a control group that has not been exposed, for agricultural and veterinary chemicals. When this type of evidence is available, it may reduce MRL values. A similar situation exists in the occupational exposure to chemicals. The Ken report (7)is an attempt to provide the best estimate of the mortality resulting fiom occupational exposure in the past. The key expression is, best estimate in this report. The best estimate of the occupational mortality to hazardous substances is 2,300 people per year. It should be noted the deaths may occur several decades after exposure to chemicals, Thee has been some criticism (8) of the best estimate value in the Kerr report. Many people consider the best estimate value to be too low; but it is the best estimate we have at the moment. 12 Safety and Chemicals 700 600 500 4-00 300 200 100 0 1940195019601970198019902OOO20102020 Year Figure 2. Incidence of mesothelioma in Australia. The evidence of mesothelioma (8), a cancer of the lining of the lung caused by asbestos, is shown in Figure 2. The peak incidence rate is predicted in 2015. The mean latency period between exposure and incidence is an astonishingly, 37 years. A further 10,OOO cases of mesothelioma are expected between 1996 and 2020. Asbestos is a hazardous substance in the national exposure standard and recognized as a category 1, carcinogen. Its use has been prohibited by State legislation. The 8-hour TWA given in the standard is 0.1 fibrelml or 100,OOO fibres/m3. It would be a brave chemical engineer to venture into an environment containing 100,OOO asbestos fibres/m3, knowing the confirmed human carcinogenic category and the sad history of the rise of mesothelioma cases. Conclusions Safety and chemicals is probably one of the most important new areas of thinking and vision for chemical engineers. There is a need to reduce the exposure of the general public and workers in the occupational environment, and to lower the adverse health effects on humans. These effects may appear only after several decades. 13 1.A. Furzer References 1. 2. 3. 4. 5. 6. 7. 8. 9. 14 Funer, RI. and Furzer, LA. 1996. Benzene: A Hazardous Air Pollutant in Australia Chemeca’96, Sydney, pp.69-73. Exposure Standards for Atmospheric Contaminants in the Occupational Environment. 1995. National Exposure Standards NOHSC: 1003 (May 1995). Crumpler, D. 1994. Chemical Crisis, Scribe Publications. Captan. 1997. Evaluation of the New Active Captan in the Product, Crop Care Captan, WG Fungicide. Australian National Registration Authority for Agricultural and Veterinary Chemicals, Public Release Summary (July). Anon. 1996. Report on the National Residue Survey, Results, Bureau of Resource Sciences. Furzer, LA. 1998. Public, Environmental and Occupational Health. Chemeca’98, Port Douglas, Queensland. Kerr, C. 1996. Best Estimate of the Magnitude of Health Effects of Occupational Exposure to Hazardous Substances, Worksafe Australia Anon. 1996. Mesothelioma cases continue to rise. Worksafe News Australia, 16-17 November. Anon. 1997. NOHSC Responds to Criticisms of OHS Statistics. Worksafe News Australia, 18-19 May.