3.2.1 Road Transport in The Netherlands

The safety of road transport in The Netherlands, like in many other countries, improved remarkably over the last 50 years [1]. More than 3000 people died in road traffic in The Netherlands annually in the 1970s. In 2010, the figure was 640. A gradual decrease in the numbers can be noticed between 2000 and 2010. In 2011, 661 people died in road traffic. The improvement is even greater on expressing the numbers per kilometer traveled because the mobility has increased over the period considered. The number of people seriously injured in road traffic, however, increased gradually from 15 424 to 20 100 between 2006 and 2011.

Three aspects are probably the most important ones concerning the safety of road transport: the design of the infrastructure, the vehicle safety, and the drivers' conduct.

The number of people who died per billion motor vehicle kilometers in The Netherlands in 2009 is 5.0. This figure is comparable to those of other developed countries.

As stated, 661 people died in road traffic in The Netherlands in 2011. That figure is made up of 231 occupants of motor vehicles, 200 cyclists, and 230 other road users.

3.2.2 Unidirectional Road Traffic in Tunnels

Modern tunnels for road traffic are built unidirectional. Thus, head‐on collisions between vehicles are impossible. That type of collision has occurred in bidirectional tunnels. A head‐on collision that has occurred in the Gotthard road tunnel in Switzerland in 2011 will be discussed shortly in this section and the Swiss Sierre tunnel will be mentioned as an example of a unidirectional tunnel in this section too.

The Gotthard road tunnel is a bidirectional tunnel and was opened in 1980. It is almost 17 km long. A collision of two trucks occurred on October 24, 2001, and caused a fire in the tunnel, killing 11 people and injuring a larger number of people. The smoke and the gases produced by the fire were the main causes of death. The effects of fires in tunnels are serious because gases and heat cannot disperse quickly and because the oxygen in the air is depleted rapidly. As the oxygen supply may be inadequate for complete combustion of combustible materials, carbon monoxide may be formed. That gas is toxic at low concentrations, e.g. a concentration of 0.4% by volume in air proves lethal in less than 1 h [2].

The Swiss Sierre tunnel is a unidirectional tunnel and was opened in 1999. It is 2.6 km long. In this type of tunnel, a head‐on collision is, as stated, impossible. However, in 2012, still, a serious accident occurred in this tunnel, which will be mentioned in Section 6.2.1.

3.2.3 Rail Transport in The Netherlands

Heavy rail in The Netherlands will be considered only in this paragraph. Light rail, i.e. underground railway and trams, will not be discussed. The safety of rail transport improved considerably after an accident at Harmelen in 1962. It was the worst train accident in The Netherlands until now. It took 93 lives and 52 people were wounded [3].

The accident occurred as follows. A fast train was on its way from Leeuwarden to Rotterdam, and, just before Harmelen, had a speed of 125 km h⁻¹. The driver missed a warning sign (yellow signal). At the place and the time of the accident, there was a dense fog. When seeing a warning sign, the driver must adapt the train's speed because the warning sign can be followed by a stop sign (red sign). However, he did not adapt the train's speed. As a matter of fact, the next sign was a stop sign. The driver then activated the brakes; however, he could not prevent the train from passing the stop sign and colliding, almost head‐on, with a stopping train from Rotterdam to Amsterdam. When the collision took place, the express still had a speed of 107 km h⁻¹.

After this accident, the Dutch government took the decision to accelerate the introduction of a safeguarding system. The Dutch acronym for this system is ATB. The objective of the system is to prevent trains from passing a stop sign (red sign). The introduction of the system took more than 30 years. In the course of the years, the original system has been further improved. The protection system informs the driver about the maximum allowable speed of the train. If the driver fails to adjust the speed, the safeguarding system brings the train to a halt. The system has two shortcomings. The first one is that the safeguarding system is not active when the train speed is lower than 40 km h⁻¹. The reasoning behind this shortcoming is as follows. If the driver has already, on approaching a stop sign, adjusted the train's speed to a speed lower than 40 km h⁻¹, it is highly unlikely that he will subsequently pass the stop sign. The second shortcoming is related to the brake‐path. A stop sign (red sign) is preceded by a warning sign (yellow). When the driver misses a warning sign, the system takes over. However, it is not always possible for the system to bring the train to a complete halt before the stop sign. Because of these two shortcomings, trains still do pass stop signs and that sometimes leads to accidents. In 2010, the number of times a train passed a stop sign was 169. Between 2001 and 2009, the annual number was greater than 200 [4]. The number has the tendency to decrease.

In 2013, it was more than 20 years ago that a rail accident occurred at which the lives of more than one passenger were taken. This figure does not include accidents at railroad crossings. In 2011, nine lives were lost due to accidents on railroad crossings. The annual number of suicides on the railroad amounts to approximately 200 [4].

3.2.4 Chlorine Transport by Rail

Akzo Nobel transported liquid chlorine by rail between plants in The Netherlands in the past. Those transports stopped in 2006. The production of chlorine by the company did not stop; however, the chemical was, as from 2006, produced and converted into other chemicals at the same site. The production of monochloroacetic acid (MCA) from acetic acid and chlorine is a typical example. Most of the MCA is used to manufacture several hundred thousand tons annually of carboxymethyl cellulose (CMC). Starch can be reacted with MCA to give carboxymethyl starch, which is as widely used as CMC. Another major application of MCA is the production of herbicides based on aryl hydroxyacetic acids.

Chlorine is very toxic [5]. The boiling point of liquid chlorine is −34.05 °C at atmospheric pressure. The saturated vapor pressure at 30 °C is about 9 bar. Thus, if liquid chlorine is not cooled, it can only be transported under pressure. If liquid chlorine is at a temperature of 30 °C and the pressure is suddenly reduced to atmospheric pressure unexpectedly, 20% of the liquid chlorine evaporates rapidly. In other words, it is then a flashing liquid. The remaining 80% then cools down to −34.05 °C and subsequently evaporates more slowly. The density of gaseous chlorine relative to air is 2.48. Thus, gaseous chlorine stays at ground level and can be displaced by the wind.

As stated, liquid chlorine is no longer routinely transported by rail in The Netherlands. Incidentally, those transports still occur. For example, Akzo Nobel buys chlorine in Germany and has it transported to Rotterdam when the chlorine plant at Rotterdam is maintained. Chlorine is transported under pressure until now. The possibility of transporting cooled, pressureless liquid chlorine by rail was discussed before 2006.

3.2.5 Sinking of the RMS Titanic in 1912

The RMS (Royal Mail Ship/Steamer) Titanic sank in the Atlantic Ocean on April 15, 1912, due to collision with an iceberg. The estimated number of people on board was 2224. This number concerns both passengers and crew. The number of people saved was 710 and the number of people having lost their life was 1514.

This accident has been investigated thoroughly and important changes to maritime regulations were recommended. This gave rise to the establishment of the International Convention for the Safety of Life at Sea (SOLAS), which is still in existence today. This Convention harmonizes maritime safety regulations internationally. It is mentioned in this context that it was agreed that radio equipment on passenger ships should be manned around the clock. The background is that, at the time of the calamity, the radio equipment of the nearby SS (Steam Ship) California was not manned. Thus, it could not receive the radio signals of the RMS Titanic. If the radio equipment of the SS California had been manned, hundreds of lives might have been saved. Furthermore, the International Ice Patrol was founded in response to the sinking of the RMS Titanic. This organization has the task of monitoring the presence of icebergs in the Atlantic and Arctic Oceans. Their movements are reported for safety reasons. Vessels that have, since 1913, heeded the Ice Patrol's published iceberg limit have not collided with an iceberg.

3.2.6 Oil Tankers with Double Hull

The United States, the European Union, and other countries have phased out or are phasing out single‐hulled tankers. In tankers of a single‐hull design, the oil in the cargo tanks is separated from the seawater by one metal wall only. In tankers of a double‐hull design, the metal wall containing the oil is protected against damage by a second metal wall at a sufficient distance from the inner wall. Two accidents with oil tankers having a single hull are recapitulated shortly.

The first accident is the Exxon Valdez oil spill [6]. The Exxon Valdez, carrying crude oil, was on its way from a pipeline terminal at Valdez, Alaska, to Long Beach, California. On March 24, 1989, it ran aground at Prince William Sound, Alaska. In order to avoid ice, the ship proceeded outside the tanker lane. The spill's volume has been estimated at 41 000 m³. The region where the ship stranded is a habitat for salmon, sea otters, seals, and seabirds. Much damage was done to the habitat. A US Coast Guard study undertaken after the accident indicated that up to 60% less oil would have entered the water if the Exxon Valdez had been equipped with a double hull.

The second accident concerns the Prestige oil spill [7]. The Prestige was on its way from St. Petersburg, Russia, to Gibraltar. It contained 77 000 tons of heavy fuel oil. It suffered severe damage during a storm off Galicia, in north‐western Spain, on November 13, 2002. The ship was 26 years old. The French, Spanish, and Portuguese governments denied the ship access to their ports. On November 19, 2002, the ship broke into two and sank in deep waters off the Galician coast. It is estimated that more than 80% of the ship's cargo has been spilled off Spain's north‐east coast. Marine life was strongly affected by the accident. It is not certain whether a double hull, with all other things being equal, would have prevented the spill.

Ships with a double hull have a second line of defense. The oil tankers with a single hull are being phased out because the release of oil generally does much damage to the environment.

3.2.7 Two Comet Accidents in 1954

Comet History

 de Havilland Aircraft Company had built only military aircraft during the Second World War. In 1945, they wanted to resume the manufacture of civil aircraft. As they had several years' experience with jet fighters, the production of civil jet aircraft was attained. The first civil aircraft with jet engines was the Comet 1. Passenger service started in May 1952. A Comet 1 aircraft is depicted in Figure 3.1.

3.2.8 Helium Gas for Zeppelins – Zeppelin Crash in 1937

On May 6, 1937, the German airship Hindenburg crashed at Lakehurst Naval Air Station in Lakehurst Borough, New Jersey, US. It took fire while trying to dock with a mooring‐mast. There were 97 people on board (36 passengers and 61 crewmen), of which 36 died. One groundsman also died. The airship could take fire because it was filled with hydrogen, an inflammable gas. Hydrogen is very easy to ignite; it has low ignition energy. The cause of the ignition has not been established with certainty although hypotheses have been put forward. It is likely that a spark due to electrostatic discharge was the cause of the ignition. American airships had helium, a noninflammable material, as carrier gas.

Helium is a much better option than hydrogen because its choice removes at least one potential cause of an accident. Still, serious accidents also occurred with helium‐filled airships.

There was a keen competition between airships (Zeppelins) and airplanes in the first half of the previous century. The Hindenburg accident marked the end of the airship era. In 1993, an initiative was taken to again start with the building and exploitation of commercial airships. The German company ZLT Luftschifftechnik, having its base at Friedrichshafen in Germany, started the project in 1993. The maiden flight of the Zeppelin NT (New Technology) was on September 18, 1997. Four years later, the Deutsche Zeppelin‐Reederei (DZR) recommenced commercial air traffic. The lift for these airships is provided by helium.

3.3.1 Cotton Spinning Plants

There was textile industry in the eastern part of The Netherlands between 1820 and 1970 [9]. Cotton mills were an important part of this industry. In these mills, cotton was spun into threads, an activity that generates a lot of inflammable dust. Typically, the buildings had four storeys. Wood was used as an important material of construction for the first generation of these cotton mills, built between 1820 and 1900. Thus, when dust was ignited, the building could take fire and burn down. As a matter of fact, one out of three to four cotton mills actually burnt down in those years. As from 1900, wood as a material of construction was replaced by cast iron, steel, and concrete. Furthermore, automatically closing doors were installed to prevent the spreading of a fire. Typically, cotton mills constructed after 1900 had a tower containing staircases with a water basin at the top (see Figure 3.2). In case of fire, water could be released from that basin via pipes attached to the ceilings to extinguish a fire. The first generation of these so‐called sprinkler installations were hand‐operated, whereas the second generation released the water automatically when solder in the water tubes melted when heated. Cotton mills were among the first industrial buildings equipped with sprinkler installations. Furthermore, cotton mills typically had a dust extraction system that passed the dust on to a dust tower.

3.3.2 Akzo Nobel Extracts Salt Without Subsidence

Akzo Nobel Industrial Chemicals extracts salt from the soil in both the eastern and northern parts of The Netherlands. This paragraph concerns extraction in the eastern part of The Netherlands in a region called Twente [10]. Specifically, the area around the towns of Enschede and Hengelo (O) is in focus. The salt is extracted by means of solution mining, water is passed down into the salt layer, and the saturated brine flows to the salt plant located at Hengelo (O). Approximately 250 million years ago, the salt layer has been formed by the evaporation of water from the sea. The salt layer is 400–500 m below the surface and is approximately 50 m thick. The extraction of salt from the specific area started in 1933. Until approximately 1980, an approach was followed that would prevent subsidence at the surface. However, on several occasions, small subsidences did occur. In 1991, a large subsidence occurred and a sinkhole was created. This occurrence gave rise to a reconsideration, and it was decided to follow a new approach. This approach comprises two safeguarding measures in series.

The first protection measure comprises a salt solution method at which at least the upper 5 m of the salt layer are left intact. The upper 5 m of the salt layer are called the roof. With this thickness, it is modeled that the roof is strong enough to prevent a collapse of the roof.

The second protection measure considers the situation if, unforeseen, a collapse of the roof having a thickness of 5 m nevertheless occurs. The reasoning is as follows. If the roof breaks down, salt from the roof and materials of the layers between the salt layer and the surface will fall into the space below the roof. However, the materials falling down will rearrange themselves. In doing so, they will occupy a larger volume than the original volume. The larger volume should guarantee that an improbable collapse of the roof should not be noticeable at the surface.

If the second safeguarding measure cannot be achieved with a roof thickness of 5 m, the roof thickness is increased to ensure that a collapse of the roof will not be noticeable at the surface. In practice, this means that most of the time the roof thickness is increased to 40–50% of the salt layer thickness.

3.3.3 Two New Cocoa Warehouses at Amsterdam in 2011

In 2003, there were two large fires in warehouses where cocoa powder was stored north of Amsterdam in The Netherlands [11, 12]. It took the fire brigade 5 days to extinguish the first fire and 8 days to extinguish the second one. Cocoa powder is a difficult product to extinguish when it has taken fire. Important aspects are that the product contains 10–20% by weight of fat and that the powder melts when the temperature is increased. The only way to stop a fire is to spread the product. Furthermore, cocoa powder is a relatively expensive product.

In 2011, Cargill Cocoa and Chocolate planned two new warehouses for cocoa powder and other cocoa products west of Amsterdam. For both warehouses, one floor having an area of 10 000 m² was envisaged. DSV Solutions at Amsterdam was asked to supervise the construction of the warehouses. That company proposed to reduce the oxygen concentration in the air in the warehouses from 21% by volume to 16–17% by volume. Experiments carried out by TNO in The Netherlands showed that the cocoa products cannot take fire at the reduced oxygen level. The reduced oxygen level is maintained by monitoring the oxygen level in the warehouses and, if need be, supplying nitrogen gas automatically from an external supply. The warehouses are airtight.

Cocoa products can, however, still smolder at the reduced oxygen level. Experiments carried out by TNO showed that smoldering stops when the oxygen level is reduced to 12% by volume by the supply of an inert gas. If smoldering is detected by instruments, carbon dioxide is led automatically into the warehouses. Carbon dioxide has been chosen for this application because it can be stored as a liquid occupying a relatively small volume.

The two warehouses have been taken into use in 2012. Generally speaking, the reduced oxygen level of 16–17% by volume is harmless for people. However, it is, in principle, not envisaged that operators enter the warehouses. The pallets with products are transported into and out of the warehouses by automatically guided vehicles (AGVs). Working with AGVs is considered safer than working with manned fork‐lift trucks. The experiences in the first two years of operation are, generally speaking, good. The new warehouses, because of the reduced oxygen level, airtightness, and AGVs, require more attention and precautions than conventional warehouses.

3.3.4 Flame Retardants

Flame retardants are chemicals that reduce the inflammability of polymers [13]. The rate of progress of a fire is substantially decreased, and, in addition, smoke development is delayed. However, flame retardants do not prevent polymers to take fire. Flame retardants started to be used on a large scale when polymeric materials replaced traditional materials such as wood and metals. This occurred in the 1970s. The new materials of construction were more combustible than the materials they replaced. Flame retardants greatly reduce the risks of fires on using polymeric materials. Television sets, carpets, and curtains are mentioned as examples of objects made from polymeric materials. As to the mechanisms, four different types can be distinguished:

1. Dilution: For example, the addition of clays to polymer systems (e.g. 50–200 parts by weight per 100 parts of polymer) reduces inflammability.
2. Generation of noncombustible gas: For example, aluminum trihydrate decomposes into aluminum oxide and water vapor at 230 °C. Typically, 50–100 parts by weight are added to 100 parts by weight of polymer.
3. Free radical inhibition: Many flame retardants consist of compounds containing bromine. These compounds generate bromic acid vapor in a fire that combines, also in the fire, with free radicals. The effect is a decrease in the rate of combustion. The free radicals are generated by the burning polymer. Some flame retardants contain chlorine instead of bromine. In this context, it is interesting to note that PVC has inherently good flame‐retardant characteristics because of the high chlorine content.
4. Solid‐phase char formation: Flame retardants acting according to this mechanism form insulating or minimally combustible chars on polymer surfaces. The char reduces volatilization of active fragments. For example, organophosphates are used as flame retardants for polyphenylene ethers and polyurethanes. Many polyphenylene ethers are engineering materials, whereas polyurethanes are used for highly elastic foams (mattresses, cushions, car seats), rigid foam (insulation mats), and rigid and flexible moldings such as steering wheels for cars.

One of the flame retardants produced by Akzo Nobel Chemicals in the past was triphenyl phosphate; it has a melting point of 48–50 °C. Flame retardants prolong the time available to escape from, e.g. a building. A further aspect is that the smoke development of a fire is strongly delayed. Most victims of a fire suffered from loss of sight with subsequent suffocation. Flame retardants that contain bromine or chlorine are being discussed at the moment because, in case of a fire, vapors that contain bromine or chlorine are generated.

3.3.5 Clamp‐on Ultrasonic Flow Measurement

Measuring the rate of flow of fluids in lines is important in many industries, e.g. in the chemical industry, power stations, and waste‐water treatment plants. Two groups of flow meters can be distinguished. The first group consists of meters in which a signal, representing the magnitude of the flow, is generated from the energy of the flowing fluid. They are called fluid‐energy‐activated flow meters. The second group of flow meters comprises meters deriving a signal from the interaction of the flow and an external stimulus. They are called external stimulus flow meters.

Clamp‐on ultrasonic flow meters belong to the second category. It is a special feature of this method that a physical contact between the measurement and the fluid processed is not necessary. Ultrasonic waves are passed through the pipe wall and the fluid and are received by external sensors.

There are two different types of ultrasonic flow meters. Transit‐time flow meters use two combinations of an ultrasonic transmitter and a receiver separated by a known distance. The difference in transit time between a signal traveling with the flow and a signal traveling against the flow is a measure of the fluid velocity. The product of the velocity and the cross‐sectional area is the volumetric flow. The volumetric flow can be converted into a mass flow when the temperature of the flow and the specific mass of the fluid as a function of temperature are known (see Figure 3.3).

The second type of ultrasonic flow meter is the Doppler flow meter. It sends an ultrasonic beam into the flow and measures the frequency shift of reflections from discontinuities in the flow. This type of flow meter is suitable for suspensions and liquids containing gas bubbles.

The transit‐time flow meter is met more often than the Doppler flow meter. Both meter types can be used for liquids and gases. However, the meter types are applied more often to liquids than to gases. The remainder of the discussion will be devoted to the transit‐time flow meter and its application to liquids.

It is often still possible to use a transit‐time flow meter when the specific mass of the liquid varies. This is the case when the specific mass can be derived from the velocity of sound through the medium. The transit‐time flow meter then also measures the velocity of sound in the medium. Temperature variations can be coped with. The temperature of the liquid is measured, and the appropriate relationship between specific mass and velocity of sound is selected.

Clamp‐on ultrasonic flow meters cannot cause leakages because there is no physical contact between the fluid and the instrument. Thus, they are safer than flow meters which are in contact with the process flow. Furthermore, they cannot suffer from corrosion or erosion and do not cause pressure loss. A further aspect is that they can relatively easily be installed in an existing plant. It is an attractive feature that they can be used for lines having a large diameter, e.g. up to 1.5 m.

It is a drawback that ultrasonic flow meters measure velocity and not mass flow. Flow meters exist that measure mass flow directly, e.g. Coriolis flow meters. Coriolis flow meters, however, are in contact with the process flow.

An example of the application of a clamp‐on ultrasonic flow meter will be given [14]. It concerns the feed line of a concentration unit for dilute sulfuric acid having a temperature of up to 115 °C and containing metal salt particles. The line material is glass‐fiber‐reinforced plastic with an internal lining of the copolymer of hexafluoropropylene and tetrafluoroethylene (FEP). The line diameter exceeds 60 cm, whereas the wall thickness is 1 cm. It is reported that the instrument functions reliably and trouble‐free as from June 2005.

3.4.1 Inundation of Part of The Netherlands in 1953

Follow‐up

 A plan was made to prevent inundations of the south‐western part of The Netherlands in the future. The plan is known as the Deltaplan, and it has been executed. It comprises, among other things, cutting off several sea arms by means of dams or barriers that can, if need be, be closed, and raise the elevation of the dikes to a safe level. The design of the dikes, dams, and barriers is based on calculated values for the failure rates of the provisions. A typical example of a failure rate will be given. The connection between Rotterdam in The Netherlands and the North Sea is called Nieuwe Waterweg (New Waterway). This connection can be closed at the seaside by means of a barrier if need be. The barrier is called Maeslantkering (see Figure 3.4). It consists of two arms that can swing from the shores and meet each other in the middle of the canal. The failure rate of this provision is once per 10 000 years [18]. The meaning of this figure is that it is expected to occur once per 10 000 years that, when the Nieuwe Waterweg has been closed, the provision is too low. There is a further aspect. The Maeslantkering is an active safeguarding step. That means that there is a certain probability that the Maeslantkering cannot be closed although closing is required and activated. That probability is approximately 0.01.

3.4.2 Replacement of Coal Gas by Natural Gas in The Netherlands

Coal gas is an inflammable gaseous fuel obtained by heating coal in the absence of air. It was the primary source of gaseous fuel until the introduction of natural gas. It is also called town gas. The replacement of town gas by natural gas in The Netherlands took place after the discovery of natural gas resources in the Northern part of the country in 1959. Similar developments occurred in other countries. Town gas contains approximately 8% by volume of carbon monoxide. Carbon monoxide is a toxic gas; a concentration of 0.4% by volume in air is fatal for humans in exposures of less than 1 h [2]. Carbon monoxide is not a poison; it is a chemical asphyxiant producing a toxic action by combining with the hemoglobin of the blood. Small amounts of carbon monoxide in the air cause toxic reactions to occur because the affinity of carbon monoxide for hemoglobin is 200–300 times that of oxygen. Over the years, town gas has caused many fatal carbon monoxide poisonings. An important part of the deaths concerned suicides.

Besides carbon monoxide, town gas contains hydrogen and methane mainly.

Natural gas is safer than town gas because it does not contain toxic components. It can cause a gas explosion; however, town gas can also cause a gas explosion. Incomplete combustion of natural gas can lead to the formation of carbon monoxide.

3.4.3 CFCs

CFCs stand for chlorofluorocarbons [19]; these compounds consist of the elements chlorine, fluorine, and carbon. Their first use was in the 1930s as refrigerants. The reason for their application was as follows. Before 1930, ammonia, sulfur dioxide, methyl chloride, propane, and butane were used as refrigerants. The first two of these compounds are toxic, whereas the other materials are inflammable. Because of these properties, a number of accidents happened. A particularly serious accident happened in a hospital at Cleveland in the United States on May 15, 1928. A leak in the hospital's methyl chloride refrigeration system caused an explosion and a fire in which 128 people died. A combination of companies decided to develop an alternative.

CFCs were the alternative, they are nontoxic, noninflammable, and have the right thermodynamic properties for refrigeration. Their introduction was successful.

In the 1950s, CFCs were introduced successfully as spray can propellants. Their physical properties made them suitable for this application. It appeared that CFCs could also successfully be used for blowing polymer foams.

In the 1970s and 1980s, it was discovered that CFCs attack the ozone in the stratosphere. Ozone absorbs harmful UV‐B radiation contained in sunlight. An increase in the number of skin cancer cases would result if more of this radiation would be present at ground level. In 1987, the Montreal Protocol, restricting the production and use of CFCs, was signed by 27 nations. The London amendments, issued in 1990, comprised a total ban on CFCs by the end of the twentieth century.

For refrigeration, CFCs were replaced by HFCs. Like CFCs, HFCs are nontoxic, are noninflammable, and have suitable properties for refrigeration. These compounds contain the elements hydrogen, fluorine, and carbon. In contrast to CFCs, they do not contain chlorine. HFCs do not deplete the ozone layer in the stratosphere.

Inflammable materials, such as dimethyl ether, have replaced CFCs as spray can propellants. HFCs could not replace CFCs for this application because they are greenhouse gases. Greenhouse gases are gases that, when present in the atmosphere, cause global warming. HFCs are at least 1000 times more potent greenhouse gases than CO₂. Different from the application as refrigerants, their use in this case would imply a deliberate emission into the atmosphere.

Materials such as carbon dioxide and cyclopentane have replaced CFCs as blowing agents for polymer foams. HFCs could not replace CFCs either in this case.

3.4.4 Dioxin in Feed

Too high dioxin levels were found in pork, poultry meat, and eggs in Germany in 2011 [20]. It appeared that fat sold by a company to a producer of cattle feed and poultry feed contained too much dioxin. The cause was that, within the premises of the latter company, vegetable fat had been mixed with fatty acid originating from the manufacture of biodiesel fuel. The dioxin levels of fatty acid originating from the manufacture of biodiesel fuel are too high and it is unsuitable for the production of cattle and poultry feed. Germany took subsequently the initiative to propose to the European Union a measure concerning companies that process both vegetable fats and so‐called technical fats. The latter fats can contain too high dioxin levels. The measure is that the production lines of vegetable fats and “technical” fats should be separated to avoid contamination. The measure applies to both storage and production equipment. Germany's proposal was accepted by the European Union [21]. The implementation of the measure took a period of less than 2 years, whereas it could normally have taken more time. Other steps and measures to prevent the presence of dioxin in food and feed were also implemented, e.g. obligatory chemical analyses.

3.4.5 Street Motor Races in The Netherlands

“Road racing” means a course on closed public road. A large number of these races were organized in the past; however, few races have survived. In The Netherlands today, two races on street circuits exist, that is, at Hengelo in the province of Gelderland and at Oss. The history of the international races at Tubbergen in The Netherlands will be reviewed shortly [22].

The circuit had the form of a triangle with the villages of Tubbergen, Fleringen, and Albergen at the angular points. It had a length of almost 10 km and had 27 bends. The races were organized between 1946 and 1984. Between 1946 and 1972, 5 persons lost their lives at the races. The number of five casualties includes a racing motorist and a spectator in 1972. The races were not organized in 1973 and 1974. A restart occurred in 1975, and the last races on the original circuit took place in 1981. The last race at Tubbergen on a different circuit occurred in 1984.

3.4.6 An Unexpected Effect: Squatters Wear Moped Safety Helmets

Mr. Marcel van Dam was Parliamentary Under‐Secretary and Minister in Dutch Cabinets in the 1970s and 1980s. He is quoted in the Dutch newspaper de Volkskrant as follows [23]: “We became conscious that many young people received brain damage at moped accidents. The Cabinet then decided to make the safety helmets obligatory. Thereupon the squatters discovered the helmet. The helmet made them unrecognizable and protected them against blows from the police. That is an effect, a change of a change, you see?”

The introduction of the protection method implied adverse effects in a different field.