About HNS

The volume of chemicals transported by sea is increasing but remains significantly lower than the seaborne trade in oil. In addition recent ITOPF experience shows that spills of bunker fuel from all types of ship are at least as likely to occur as loss of cargo oil from a tanker. Consequently chemical spills occur at a much lower frequency than spills of oil. However, the consequence of a chemical spill can be more wide reaching than that of oil and there is growing international awareness of the need for safe and effective contingency arrangements for chemical spills. The wide variety of chemicals transported, their varying physical and chemical properties, the different ways in which they behave in the environment and the potential for effects on human health mean that response to chemical spills is not as straightforward as for oil.

 

What are Hazardous and Noxious Substances (HNS)?

A Hazardous and Noxious Substance is a term used to describe a substance other than oil which, if introduced into the marine environment is likely to create hazards to human health, to harm living resources and marine life, to damage amenities or to interfere with other legitimate uses of the sea.

Whether a substance is classed as hazardous or noxious is largely determined by its inclusion in one or more lists found in a number of IMO Conventions and Codes (see Table 1) designed to ensure maritime safety and prevention of pollution. If the chemical transported has one or more of the following properties, it is likely to be considered as a ‘hazardous and noxious substance’. (Radioactive and infectious substances are outside the scope of the HNS regime.)

  • Flammable
  • Explosive
  • Toxic
  • Corrosive
  • Reactive

Table 1: Examples of IMO Conventions and Codes providing HNS lists  

Material

Conventions & Codes

Bulk Liquids

Chapter 17 of International Code for the Construction and Equipment of Ships Carrying Dangerous Chemicals in Bulk (IBC Code)

   
Gases Chapter 19 of International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC Code)
   

Solids in bulk

Appendix 9 of Code of Safe Practice for Solid Bulk Cargoes (BC Code) if also covered by IMDG Code in packaged form

   
Packaged goods International Maritime Dangerous Goods Code (IMDG Code)

 

Human Health Aspects

Manufacturers of Hazardous and Noxious Substances typically provide Material Safety Data Sheets (MSDS) which summarise the specific hazards associated with each substance. Over time these will be replaced by Safety Data Sheets (SDS) under the UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS)*. GHS classifies chemicals by the types of hazard they represent and proposes harmonized hazard communication by consistent labelling and safety data sheets. It aims at ensuring that information on physical hazards and toxicity from chemicals is available to enhance the protection of human health and the environment during the handling, transport and use of these chemicals.

MSDS and SDS both follow the same format and provide the following information:

 

1. Identification

9. Physical & chemical properties

2. Hazard(s) identification

10. Stability & reactivity

3. Composition/ingredients

11. Toxicological information

4. First-aid measures

12. Ecological information

5. Fire-fighting measures

13. Disposal considerations

6. Accidental release measures

14. Transport information

7. Handling & storage

15. Regulatory information

8. Exposure controls/personal protection

16. Other information 

 

Effects on Marine Resources

The effects of a chemical lost into the marine environment depend on a number of factors such as the toxicity of the material, the quantities involved and resulting concentrations in the water column, the length of time biota are exposed to that concentration and the sensitivity of the organisms to the particular chemical. Dilution is brought about by water movement due to tidal flow, ocean currents and turbulent diffusion but even if the concentration is below what would be considered lethal, sub-lethal concentrations can still lead to longer term impacts. Chemically-induced stress can reduce the overall ability of the organism to reproduce, grow, feed or otherwise function normally. The characteristics of some chemicals, particularly metals and some organic compounds, can result in the bio-accumulation of these materials. Sessile marine organisms that filter seawater for food, such as shellfish, are particularly vulnerable to this phenomenon. Bio-magnification may follow if the materials pass up the food chain.   

 

GESAMP

The effects of chemicals on the marine environment have been summarised by GESAMP (the Group of Experts on Scientific Aspects of Marine Environmental Protection www.gesamp.net), an advisory body to the United Nations established in 1969. GESAMP comprises experts, drawn from a wide range of relevant disciplines, but who act in their individual capacity. GESAMP has published a Hazard Evaluation of Substances Transported by Ships for the most commonly transported chemicals. The properties of the chemicals have been evaluated in relation to a number of predefined effects should any of the listed chemicals be spilt at sea:

  • Bioaccumulation
  • Biodegradation
  • Acute and chronic toxicity on marine organisms
  • Long term health effects on humans
  • Effects on marine wildlife, and on benthic habitats
  • Effect on other marine resources

This easily accessible and simple guide provides an important first step in evaluating the severity of a spill.

MARPOL

The MARPOL Convention is the main international convention covering prevention of pollution from the shipping industry. Within MARPOL are two annexes that are directly relevant to HNS:

Annex II

MARPOL Annex II contains regulations for bulk liquid cargos that may cause environmental pollution if lost at sea. Within the annex are four categories that are graded depending on the hazard the bulk liquid presents to marine resources, human health and amenities.

  • Category X – liquid substances which are deemed to present a major hazard  to either marine resources or human health, and therefore justify the prohibition of the discharge into the marine environment.
  • Category Y – liquid substances which are deemed to present a hazard to either marine resources or human health or cause harm to amenities or other uses of the sea and therefore justify a limitation on the quality and quantity of the discharge into the marine environment.
  • Category Z – liquid substances which are deemed to present a minor hazard to either marine resources or human health and therefore justify less stringent restrictions on the quality and quantity of the discharge into the marine environment.
  • Category OS – these “other substances” are deemed to fall outside of categories X, Y, and Z and are deemed to present no harm to marine resources, human health, amenities or other uses of the marine environment.

 

Annex III

marine pollutant symbol

Annex III deals with the provisions for the prevention of pollution by harmful substances carried by seas in packaged form. As part of these regulations, any compounds that are environmentally harmful (known as marine pollutants) must be clearly marked and labelled as a ‘marine pollutant” (see Figure 1) to distinguish them from less harmful cargos.

Fate of Chemicals in the Marine Environment

Physical Behaviour

When chemicals are spilt, they behave in a number of different ways. It is important to understand this behaviour, not only so that human health and safety implications are recognised but also to decide on the most effective response.

 

In simple terms, a substance behaves in one or more of five ways when spilt:

  • Dissolve
  • Evaporate
  • Float
  • Gas
  • Sink
processes acting on chemical spill
Figure 2: Processes that can act on a chemical spilt into the marine environment

Classifying the substances depending on the properties they exhibit when released into the marine environment is a useful response tool. The ‘fate’ of a substance is determined by the properties of volatility, solubility and density and in turn, the nature of the hazard presented by the substance (toxicity, flammability, reactivity, explosive, corrosive, etc). It also defines the most appropriate technique in dealing with it, e.g. it may be possible to contain and recover a chemical classed as a “floater” using a boom.

 

The classification system covers gases, liquids and solids. HNS showing similar behaviour in water can be grouped together and classified into the following 12 groups on the basis of the five behavioural characteristics – See Table 3. However, it is important to be aware that this system only classifies chemicals according to their major property/properties relevant to spill response and a chemical may also exhibit other properties e.g. Benzene is classed according to its major property (evaporator) but it is also soluble to a certain extent and so this too may need to be considered.

Table 3: the European Classification System for chemicals

Property Group

Properties

G          

gas

evaporate immediately

GD       

gas/dissolver

evaporate immediately

E          

evaporator

float, evaporate rapidly

ED

evaporator/dissolver

evaporate rapidly, dissolve

FE            

floater/evaporator

float, evaporate

FED     

floater/evaporator/dissolver                     

float, evaporate, dissolve

F          

floater

float

FD       

floater/dissolver

float, dissolve

DE       

dissolver/evaporator

dissolve rapidly, evaporate

D          

dissolver

dissolve rapidly

SD       

sinker/dissolver

sink, dissolve

S          

sinker

sink

 

Chemical Response Strategies

Once the main physical and chemical properties, and hence the behaviour of a spilt substance are known and the likely impacts to human health and marine resources have been taken into account, a suitable response can be considered. A brief summary of potential response techniques for the different groups of chemicals is given below. However, the response strategy eventually implemented will also be largely dependant on the specific circumstances of the incident.

 

Gas & Evaporators- the release of a gas or chemical substance evaporating under the weather conditions prevailing at the time have the potential to generate large vapour clouds that might be toxic or form an explosive mixture with air. As a result, there may be potential health and safety implications for the vessel crew, responders and population nearby.

In order to plan a response, it is important to know how the gas or vapour will behave and the likely trajectory of the hazardous cloud. Relevant computer modeling of the spreading of airborne contaminants is likely to help to forecast the movement and fate of the plume as it disperses. Appropriate safety zones can then be put into place as necessary and the public advised as appropriate.

Issuing advice to the public to remain indoors for a short period may be given by the authorities.  If the chemical is of a flammable nature, then all ignition sources must be eliminated. Techniques such as trying to “knock down” a water-soluble vapour cloud or trying to stop or deflect it using water sprays are other measures that may be available to responders. In such incidents occurring near populations, the fire brigade are likely to have the commanding role in the response.

In any case, responders must wear the appropriate Personal Protective Equipment (PPE) and response / monitoring crafts must be adequately designed should they need to enter the hazardous atmosphere. 

Chemicals that dissolve – A dissolving chemical will form a growing ‘plume’ of decreasing concentration in the water and eventually dilute. It is important to monitor the concentrations in the water to track the movement of the chemical and therefore to predict any hazard that may arise to the environment, fisheries, fresh water intakes, recreational areas, etc. Again, relevant computer models can give useful indications on the likely fate of the substance.

The ability to contain and recover dissolved chemicals is extremely limited. Providing means to accelerate the natural processes of dispersion and dilution may be the only way to respond to such chemicals. Some dissolved chemical plumes may, in theory, be neutralised, oxidised, flocculated or reduced by the application of other chemicals. However, careful assessment of feasibility and expected efficiency in an open environment as well as approval of the relevant authorities is usually required before this response method is employed.

Chemicals that float - Chemicals that float will spread under the effect of gravity to form a slick in a similar way to oil. However, unlike oil they may not be visible on the water. Nevertheless, in some cases remote sensing techniques may be employed to detect and monitor floating materials.

Floating chemicals can be low or high viscosity liquids, or may even be solid. If the spilt chemical has a high vapour pressure it may evaporate quickly and form a gas cloud above the slick. In such cases air quality monitoring is usually undertaken to assess fire, explosion and toxicity risks,.

It may be possible to consider deploying booms to contain and control the movement of substances over the water surface. Skimmers and other oil spill response equipment may also be used to recover the material from the surface of the water. However, it is important to make sure, prior to use, that the spilt chemical will not react with the equipment by taking into account the chemical’s reactivity. Alternatively, emergency responders may have fire-fighting or suppressant foams that can be applied to reduce the evaporation and the risk of fire/explosions.

Again, responders must wear the appropriate Personal Protective Equipment and response / monitoring crafts must be adequately designed should they need to enter a hazardous atmosphere.

Chemicals that sink – Chemicals that sink have the potential to contaminate the seabed, and sometimes to persist in the sediment. The response to sunken chemicals may, therefore, need to consider the recovery of the chemical and any heavily contaminated sediment. Careful attention will also need to be paid to the removal and disposal of these contaminated sediments.

In shallow waters, mechanical dredgers and pump/vacuum devices may be used to recover sunken substances. The use of submersibles and remotely controlled underwater cameras may identify and recover chemicals on the seabed.

 

Introduction to GHS:- http://www.unece.org/trans/danger/publi/ghs/ghs_welcome_e.html

 

Bioaccumulation refers to the build up of a substance within a living organism, or certain tissues of a living organism, due to the rate of uptake of that substance being greater than the rate of elimination by metabolic transfer or excretion. The term tends to be associated with certain lipid-soluble organic chemicals that are not readily metabolised by living organisms such as pesticides (e.g. DDT) and organometallic compounds such as methylmercury and tetra-ethyl lead (TEL).

 

Biomagnification refers to the sequential build up of a bioaccumulative substance up the food chain through predation.  Typically the highest concentrations of the substance are found within the tissues of the top predators within the food chain.

NB: Bioaccumulation occurs within a trophic (food chain) level. Biomagnification occurs across trophic (food chain) levels.