Carson Ph., Mumford C. Hazardous Chemicals Handbook (Справочник по опасным химическим веществам)
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Generally, sampling of waterways should be at the fastest flowing part of the stream/river,
usually mid-depth unless the contaminant is less dense than water and could float, or is more
dense and could accumulate near the river bed. For lakes representative samples should be taken
near to the inflow, outflow and other locations. If two phases are present both may require
sampling. Sample preservation by refrigeration, pH adjustment, elimination of light, filtration,
and extraction may be important.
Table 10.34 summarizes the information to be recorded during an investigation. (A code of
practice for the identification of potentially contaminated land and its investigation is given in
British Standard DD 175/1988.) Consideration should be given to the application of appropriate
quality control and quality assurance procedures such as those advocated by ‘good laboratory
practice’ or ISO 17025 to ensure the sampling, the analysis and interpretation/reporting of data
are robust since results will dictate action and may be subject to scrutiny by third parties. Duplicate
samples may need to be retained for disclosure to third parties. There may be legal requirements
to notify results to relevant authorities.
POLLUTION MONITORING STRATEGIES IN INCIDENT INVESTIGATION 389
11
Radioactive chemicals
The main chemical elements are listed in Chapter 18. Each comprises a nucleus of positively-
charged protons and neutral neutrons orbited by negative electrons. The mass number A is given
by
A = Z + N
where Z is the number of protons, or atomic number
N is the number of neutrons.
Atoms with the same value of Z but different values of A are isotopes (Table 11.1). Many isotopes
are stable but others are naturally or artificially radioactive, i.e. their atomic nuclei disintegrate,
emitting particles or radiation. This changes the nuclear structure of the atom and often results in
the production of a different element.
Table 11.1 Nuclear composition of selected istopes
Element Symbol Atomic Protons Neutrons Total number Atomic
number of protons weight
and neutrons
Hydrogen
1
1
H
1 1 1 1.0080
(Deuterium)
1
2
H
1112
Carbon
6
12
C
6 6 6 12 12.010
6
13
C
66713
6
14
C
66814
Nitrogen
7
13
N
7 7 6 13 14.008
7
14
N
77714
7
15
N
77815
Chlorine
17
35
Cl
17 17 18 35 35.457
17
37
Cl
17 17 20 37
Lead
82
206
Pb
82 82 124 206 207.21
82
207
Pb
82 82 125 207
82
208
Pb
82 82 126 208
Uranium
92
234
U
92 92 142 234 238.07
92
235
U
92 92 143 235
92
238
U
92 92 146 238
Natural sources of ionizing radiation include cosmic rays and nucleides such as potassium-40,
carbon-14 and isotopes of thorium and uranium which are present in rocks, earth and building
materials. Industrial sources of radiation include nuclear reactors, X-ray radiography, electron
microscopy, X-ray diffractors, thickness gauges, smoke detectors, electron beam welding and
certain processes including chemical analysis, polymer curing, chemical/biological tracing, food
and medical sterilization, and mining. The radiation source can be sealed, when the radiation can
be switched off, or unsealed. Examples of the former are smoke detectors and electrical devices
for producing radiation.
Hazards
The chemistry, and hence hazards, of ‘hot’, or radioactive, elements parallel those of their ‘cold’
isotopes. However, the radiation poses additional toxicity hazards. A qualitative classification of
selected isotopes in terms of toxicity is given in Table 11.2. The biological effects of ionizing
radiation stem mainly from damage to individual cells following ionization of the water content.
Oxidizing species, e.g. hydrogen peroxide, form together with ions and free radicals, all capable
of chemical attack on important organic moieties within the cells, e.g. nucleic acids. Biological
effects are influenced by the type of radiation, the dose, duration of exposure, exposed organ and
route of entry. Effects on cells include death, mutation and delayed reproduction. Acute adverse
effects of exposure are illustrated in Table 11.3.
Table 11.2 Classification of isotopes according to relative radiotoxicity per unit activity
The isotopes in each class are listed in order of increasing atomic number
Very high toxicity Sr-90 + Y-90, *Pb-210 + Bi-210 (Ra D + E), Po-210, At-211, Ra-226 + 55 per cent *daughter
products, Ac-227, *U-233, Pu-239, *Am-241, Cm-242.
High toxicity Ca-45, *Fe-59, Sr-89, Y-91, Ru-106 + *Rh-106, *I-131, *Ba-140 + La-140, Ce-144 + *Pr-144, Sm-
151, *Eu-154, *Tm-170, *Th-234 + *Pa-234, *natural uranium.
Moderate toxicity *Na-22, *Na-24, P-32, S-35, Cl-36, *K-42, *Sc-46, Sc-47, *Sc-48, *V-48, *Mn-52, *Mn-54, *Mn-
56, Fe-55, *Co-58, *Co-60, Ni-59, *Cu-64, *Zn-65, *Ga-72, *As-74, *As-76, *Br-82, *Rb-86,
*Zr-95 + *Nb-95, *Nb-95, *Mo-99, Tc-98, *Rh-105, Pd-103 + Rh-103, *Ag-105, Ag-111, Cd-
109 + *Ag-109, *Sn-113, *Te-127, *Te-129, *I-132, Cs-137 + *Ba-137, *La-140, Pr-143, Pm-
147, *Ho-166, *Lu-177, *Ta-182, *W-181, *Re-183, *Ir-190, *Ir-192, Pt-191, *Pt-193, *Au-
196, *Au-198, *Au-199, Tl-200, Tl-202, Tl-204, *Pb-203.
Slight toxicity H-3, *Be-7, C-14, F-18, *Cr-51, Ge-71, *Tl-201.
*Gamma-emitter.
Types of radiation
The nature of the radioactive decay is characteristic of the element; it can be used to ‘fingerprint’
the substance. Decay continues until both the original element and its daughter isotopes are non-
radioactive. The half-life, i.e. the time taken for half of an element’s atoms to become non-
radioactive, varies from millions of years for some elements to fractions of a second for others.
1. α-Particles (helium nuclei, i.e. 2 neutrons plus 2 protons): on emission the original isotope
degrades into an element of two atomic numbers or less, e.g. uranium 238 produces thorium 234.
Such transformations are usually accompanied by γ-radiation or X-radiation. α-Particles have a
velocity about one-tenth that of light with a range in air of 3–9 cm. Because of their relatively
TYPES OF RADIATION 391
392 RADIOACTIVE CHEMICALS
large size and double positive charge they do not penetrate matter very readily and are stopped by
paper, cellophane, aluminium foil and even skin. If inhaled or ingested, however, absorption of α-
particles within tissues may cause intense local ionization.
2. β-Rays comprise electrons of velocity approaching that of light with a range of several
metres and an energy of 0–4 MeV. β-Particles of <0.07 MeV do not penetrate the epidermis
whereas those >2.5 MeV penetrate 1–2 cm of soft tissue. Thus β-emitters pose both an internal
and an external radiation hazard: skin burns and malignancies can result. Once inside the body
they are extremely hazardous, though less so than γ-rays. About 1 mm of aluminium is needed to
stop these particles. Most β-emissions are accompanied by γ- or X-radiation and result in
transformation into the element of one atomic number higher or lower but with the same atomic mass.
3. γ-Radiation is similar to, but shorter in wavelength than, X-rays and is associated with many
α- or β-radiations. γ-Radiation does not transform isotopes/elements. Like X-rays, γ-rays are very
penetrating; they are capable of penetrating the whole body and thus require heavy shielding, e.g.
γ-rays from
60
Co penetrate 15 cm steel.
4. X-Radiation like γ-radiation is electromagnetic in nature. It can be emitted when β-particles
react with atoms. More often it is electrically generated by accelerating electrons in a vacuum
tube. The latter source can be switched off. X-rays are extremely penetrating and are merely
attenuated by distance and shielding.
5. Neutron radiation is emitted in fission and generally not spontaneously, although a few
heavy radionucleides, e.g. plutonium, undergo spontaneous fission. More often it results from
bombarding beryllium atoms with an α-emitter. Neutron radiation decays into protons and electrons
with a half-life of about 12 min and is extremely penetrating.
The same type of radiation emitted by different isotopes may differ significantly in energy, e.g.
γ-radiation from potassium-42 has about four times the energy of γ-radiation from gold-198.
Units of radiation are the becquerel (Bq), the gray (Gy) and the sievert (Sv).
Control measures
The control of ionizing radiation is heavily regulated. Expert advice should be sought prior
to introducing sources of radiation onto the premises. The general provisos for their control
are that:
• All practices resulting in exposure shall be justified by the advantages produced.
• All exposures shall be as low as reasonably practicable.
Table 11.3 Effects of acute exposures to X- and γ-radiation
Dose Effects
(Gy)
<1 No clinical effects but small depletions in normal white cells count and in platelets likely within 2 days.
1 About 15% of those exposed show symptoms of loss of appetite, nausea, vomiting, fatigue etc. 1 Gy delivered
to whole body or 5 Gy delivered to bone marrow produces leukaemia.
2 Some fatalities occur.
3.5–4 LD
50
(see Ch. 5), death occurring within 30 days. Erythema (reddening of skin) within 3 weeks.
7–10 LD
100
, death occurring within 10 days.
• The dose received shall not exceed specified limits. As with most hygiene standards these
limits vary slightly between nations: local values should be consulted. Limits set within the UK
are summarized in Table 11.4.
• All regulatory requirements will be followed.
• All incidents will be investigated and reported.
Table 11.4 UK exposure limits (the Ionizing Radiations Regulations, 1999)
Dose (mSv in any Employee aged 18 or Trainee under 18 All others
calendar year) over
Whole body 20* 6 1
Equivalent dose for the
Lens of eye 150 50 15
Skin** 500 150 50
Arms, forearms, feet, ankles 500 150 50
Abdomen of women of child bearing 13***
capacity at work (in any consecutive
period of 3 months)
* Where these limits are impracticable having regard to the nature of the work the employer may apply a dose limit of
100 mSv in any period of 5 consecutive months subject to a maximum effective dose of 50 mSv in any single calendar year,
and to prior approval by the Radiation Protection Adviser, the affected employee(s), and the Health and Safety Executive.
** As applied to the dose averaged over an area of 1 cm
2
regardless of area exposed.
*** Once an employer has been informed that an employee is pregnant the equivalent dose to a foetus should not exceed
1 mSv during the remainder of the pregnancy and significant bodily contamination of breast-feeding employees must be
prevented.
In the UK, annual doses of 20 mSv, or any case of suspected overexposure, must be investigated,
reported and recorded. The HSE must also be notified of any spillages of radioactive substance
beyond specified amounts. Companies are obliged to monitor exposures and investigate excursions
beyond action limits, and to maintain records for specified periods. Checks on surface contamination
are aimed at avoiding exposure, preventing spread of contaminant, detecting failures in containment
or departures from good practice, and providing data for planning further monitoring programmes.
Air monitoring will be required, e.g., when volatiles are handled in quantity, where use of
radioactive isotopes has led to unacceptable workplace contamination, when processing plutonium
or other transuranic elements, when handling unsealed sources in hospitals in therapeutic amounts,
and in the use of ‘hot’ cells/reactors and critical facilities. Routine monitoring of skin, notably the
hands, may be required.
Monitoring for both external and internal radiation may be required, e.g. when handling large
quantities of volatile ‘hot’ chemicals or in the commercial manufacture of radionucleides, in
natural and enriched uranium processes, in the processing of plutonium or other transuranic
elements, and in uranium milling and refining. The nature of biological monitoring is influenced
by the isotope: e.g., faeces, urine and breath monitoring is used for α- and β-emitters and whole-
body monitoring for γ-sources.
Exposure is minimized by choice of source, by duration of exposure, by distance from source
(at 1 m the radiation level is reduced almost 10-fold), and by shielding. The greater the mass per
unit area of shield material the greater the shielding efficiency. Whereas α- and β-particles pose
few problems (the former can be absorbed by, e.g., paper and the latter by 1 cm Perspex) γ- and
X-rays are not completely absorbed by shield material but attenuated exponentially such that
radiation emerging from the shield is given by:
CONTROL MEASURES 393
394 RADIOACTIVE CHEMICALS
D
t
= D
0
e
–ut
where D
0
is the dose without a shield
D
t
is the dose rate emerging from a shield of thickness t
u is the linear absorption coefficient of shield material.
Half-thickness values (H-TV) i.e. thickness to reduce intensity to half the incidence value, for
materials commonly used as shields for selected γ-rays are exemplified by Table 11.5.
Table 11.5 Approximate half-thickness values for a selection of shield materials and γ-emitters
Nucleide Half-life
γ
-energy H-TV
(cm)
(MeV)
Concrete Steel Lead
137
Cs 27 years 0.66 4.82 1.63 0.65
60
Co 5.24 years 1.17–1.33 6.68 2.08 1.20
198
Au 2.7 days 0.41 4.06 – 0.33
192
Ir 74 days 0.13–1.06 4.32 1.27 0.60
226
Ra 1622 years 0.047–2.4 6.86 2.24 1.66
Table 11.6 General control measures for work with radioactive substances
Consult experts including competent authorities (in UK the HSE must be given 28 days prior notice of specified work with
ionizing radiation).
Conduct a risk assessment to any employee and other persons to identify measures needed to restrict exposure to ionizing
radiation and to assess magnitude of risk including identifiable accidents.
Conduct work in designated controlled areas (e.g. in UK these are areas in which instantaneous dose rates >7.5 µSv/hour
occur, or where employees may exceed 6 mSv annual dose limit, or where air concentration or surface contamination
exceeds specified levels).
Provide barriers for identification and display of appropriate warning notices, e.g. Trefoil symbol.
Control exposures by engineering techniques, e.g. containment, shielding, ventilation (consider need for in-duct filters to
remove contamination prior to exhausting to atmosphere), backed up by systems of work and personal protection
including approved respirators where necessary.
Use remote handling techniques where necessary.
Appoint a Radiation Protection Adviser: all staff involved with radioactive work should be adequately trained and instructed.
Limit access to designated areas to classified persons (e.g. in UK persons likely to receive doses in excess of 6 mSv per year
or an equivalent dose which exceeds 30% of relevant hygiene standard). Access may need to be limited by trapped keys
or interlocks for high dose rate enclosures.
Prepare as appropriate written rules for work in designated areas and appoint Radiation Protection Supervisors.
Check exposures routinely by personal dosimetry or following accidents (in the UK dosimetry services must be approved) and
keep records (e.g. in UK for at least 50 years). Notify the relevant employees and authorities as appropriate. Monitor
background contamination periodically using equipment that has been checked by qualified persons and keep records
of levels (e.g. for 2 years).
Investigate accidents which may have led to persons receiving effective doses in excess of 6 mSv or an equivalent dose
greater than 30% of any relevant dose limit. Investigate and report to the authorities loss of materials from accidental
release to atmosphere, spillages, theft. The Regulations provide a comprehensive list of notifiable concentrations for each
radionuclide isotope.
Provide mandatory medical surveillance for classified workers, e.g. medical examinations prior to commencement of
radioactive work followed by check-ups annually or when overexposure may have occurred. (In the UK the surveillance
must be undertaken by appointed doctors and records retained for at least 50 years.)
Maintain high standards of personal hygiene and housekeeping.
Detailed precautions for handling radioactive substances will be dictated by the nature and
quantity of isotope and the likely level of exposure. Thus for some materials laboratory coats and
gloves may be adequate; for others a fully enclosed suit and respirator may be more appropriate.
Some general precautions are listed in Table 11.6.
Do not eat, drink, smoke, apply cosmetics or use mouth pipettes in controlled areas. Dress any wounds prior to entering the
area.
Wherever practicable, store radioactive substances in sealed, properly labelled containers. Check for leaks periodically (e.g.
2-yearly intervals) and maintain records of stocks including sealed sources (e.g. for 2 years).
Carry out work over spill trays to contain leakages and use impervious work surfaces.
Decontaminate apparatus and prevent cross-contamination.
Collect waste for treatment or disposal and deal with spillages immediately.
Remove protective clothing in a changing area provided with wash basin, and lockers for clean and dirty clothing.
Table 11.6 Cont’d
CONTROL MEASURES 395
12
Safety by design
Plant and equipment design are regulated by substantial legislation. In the UK this includes: The
Health and Safety at Work etc. Act 1974, the Provision and Use of Work Equipment Regulations
1998, the Control of Substances Hazardous to Health Regulations 1999, the Factories Act 1961,
the Electricity at Work Regulations 1989, the Fire Precautions Act 1971, together with specific
legislation, e.g. the Highly Flammable Liquids and LPG Regulations 1972.
Common matters, e.g. ventilation, temperature and lighting; floor, wall and ceiling surfaces;
workspace allocation; workstation design and arrangement; floors and traffic routes; safeguards
against falls or being struck by a falling object; glazing; doors and gates; travelators and escalators;
sanitary and washing facilities; drinking water supply; accommodation for clothing; facilities for
changing, resting and meals; are all covered by the Workplace (Health, Safety and Welfare
Regulations) 1992.
Design procedures
To ensure safety consult flowsheets/engineering line diagrams and consider both the materials
(raw materials storage, processing, product storage, disposal and transportation) and the process
details (scale, batch vs continuous, temperature, pressure, materials of construction, monitoring,
safety features, e.g. fail-safe or ‘second chance’ design). See Table 12.1. Subject the proposals to
detailed scrutiny, as in Table 12.2 or using a HAZOP study, fault tree analysis, etc. for both the
planned operation and anticipated major deviations from normal operation (Table 12.3).
A HAZOP (Hazard and Operability Study) involves a formal review of process and instrumentation
diagrams by a specialist team using a structured technique, based upon key words. These comprise
‘property words’ and ‘guide words’, e.g. as in Table 12.4.
Where possible plants of intrinsically safe design are preferred, i.e. those which have been
designed to be ‘self-correcting’ rather than those where equipment has been ‘added on’ to control
hazards. Some characteristics of intrinsically safe plants are:
• Low inventory (small plant with less inherently hazardous materials on site).
• Substitution of hazardous materials with less dangerous chemicals.
• Attenuation of risk by using hazardous materials in the least dangerous form.
• Simplification of plant, instrumentation, operating procedures to reduce the chance of human
error.
• Domino effects eliminated so that adverse events are self-terminated and do not initiate new
events.
• Incorrect assembly of plant made impossible by equipment design.
Table 12.1 Some considerations in reaction process selection and design
Are unstable reactions and side reactions possible, e.g. spontaneous combustion or polymerization?
Could poor mixing or inefficient distribution of reactants and heat sources result in undesirable side reactions, hot spots,
runaway reactions, fouling, etc?
Can hazards from the reaction be reduced by changing the relative concentration of reactants or other operating conditions?
Can side reactions produce toxic or explosive material, or cause dangerous fouling?
Will materials absorb moisture from the air and then swell, adhere to surfaces, form toxic or corrosive liquid or
gas, etc?
What is the effect of impurities on chemical reactions and upon process mixture characteristics?
Are materials of construction compatible mutually and with process materials?
Can dangerous materials build up in the process, e.g. traces of combustible and non-condensible materials?
What are the effects of catalyst behaviour, e.g. aging, poisoning, disintegration, activation, regeneration?
Are inherently hazardous operations involved:
Vaporization and diffusion of flammable/toxic liquids or gases?
Dusting and dispersion of combustible/toxic solids?
Spraying, misting or fogging of flammable/combustible materials or strong oxidizing agents?
Mixing of flammable materials and combustible solids with strong oxidizing agents?
Separation of hazardous chemicals from inerts or diluents?
Increase in temperature and/or pressure of unstable liquids?
• The status of plant should be immediately obvious.
• The tolerance should be such that small mistakes do not lead to major problems.
• Leaks should be small.
Table 12.5 summarizes the application of these principles (after Kletz – see Bibliography). Where
this approach is not feasible, external features of plant must ensure the minimization of unwanted
consequences.
Layout
Factory layout has a significant bearing on safety. Relevant considerations include:
• Relative positions of storage and process areas; control room, laboratories and offices – i.e.
areas of highest population density; switch-house; materials receipt and despatch areas; effluent
treatment facilities. Spacing distances according to standard guidelines.
• Need for normal and emergency access (and escape).
• Security, e.g. fencing requirement, control of access.
• Topography.
• Tendency for flooding.
• Location of public roads.
• Prevailing wind direction.
• Zoning of electrical equipment (Table 12.6).
• Positions of neighbouring developments, housing, public roads, controlled water courses, etc.
Segregation is practised to allow for housekeeping, construction and maintenance requirements
and to reduce the risk of an accident resulting in a ‘domino effect’, e.g. from a fire, explosion or
toxic release. For very toxic substances, e.g. prussic acid (HCN) or tetraethyl lead, this may
involve isolating the entire manufacturing operation in a separate unoccupied building or sealed-
off area.
LAYOUT 397
398 SAFETY BY DESIGN
Table 12.2 Chemical process hazard identification
Materials and reaction Identify all hazardous process materials, intermediates and wastes
Produce material information sheets for each process material
Check the toxicity of process materials, identify short and long term effects for various modes
of entry into the body and different exposure tolerance
Identify the relationship between odour and toxicity for all process materials
Determine the means for industrial hygiene recognition, evaluation and control
Determine relevant physical properties of process materials under all process conditions,
check source and reliability of data
Determine the quantities and physical states of material at each stage of production, handling
and storage, relate these to the danger and second-degree hazards
Identify any hazard the product might present to transporters and public while in transit
Consult process material supplier regarding properties, characteristics, safety in storage, handling
and use
Identify
all
possible chemical reactions, both planned and unplanned
Determine the inter-dependence of reaction rate and variables, establish the limiting values to
prevent undesirable reactions, excessive heat development etc.
Ensure that unstable chemicals are handled so as to minimize their exposure to heat, pressure,
shock and friction
Are the construction materials compatible with each other and with the chemical process
materials, under all foreseeable conditions?
Can hazardous materials build-up in the process, e.g. traces of combustible and noncondensible
materials?
General process Are the scale, type and integration of the process correct, bearing in mind the safety and
specification health hazards?
Identify the major safety hazards and eliminate them, if possible
Locate critical areas on the flow diagrams and layout drawings
Is selection of a specific process route, or other design option, more appropriate on safety
grounds?
Can the process sequence be changed to improve the safety of the process?
Could less hazardous materials be used?
Are emissions of material necessary?
Are necessary emissions discharged safely and in accordance with good practice and legislation?
Can any unit or item be eliminated and does this improve safety, e.g. by reducing inventory
or improving reliability?
Is the process design correct?
Are normal conditions described adequately?
Are all relevant parameters controlled?
Are the operations and heat transfer facilities properly designed, instrumented and controlled?
Has scale-up of the process been carried out correctly?
Does the process fail safe in respect of heat, pressure, fire and explosion?
Has second chance design been used?
Spacing distances may be reduced in the light of:
• explosion relief, blast-proofing, blast walls, earth banks;
• bunds, dykes;
• steam and water curtains; foam blanketing provisions;
• inter-positioning of sacrificial plant, e.g. cooling towers, unpopulated buildings;
• provision of refuges, e.g. for toxic release incidents.
Adequate distance frequently serves to mitigate the consequences of an accidental release of
chemicals, e.g. a flammable liquid spillage or toxic gas escape.
Distances are recommended for zoning of electrical equipment, separation of storage from
buildings etc. Distances are also proposed (on the basis of experience) to minimize the escalation