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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.
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