VOCs in Construction

According to the WHO -World Health Organization-, indoor air quality is recognized as a significant risk factor for human health. [1]

People spend approximately 90% of their time indoors, whether at home, at work, or in leisure or recreational spaces. These spaces not only accumulate pollutants from outside but can also have an inadequate indoor environment or sources of pollutant emissions.

Among the pollutants present in our indoor environments, Volatile Organic Compounds (VOCs) stand out. This definition groups various sets of chemical particles emitted by construction materials, coatings, paints, and other elements such as furniture, fabrics, or cleaning products that remain present in the environment or on surfaces and can correspond to different classes of chemicals.

INDOOR ENVIRONMENTAL QUALITY

Studies estimate that people in developed countries spend approximately 58% to 78% of their time in domestic or work environments [2]. For this reason, the environmental quality of these spaces, to which users are constantly exposed, becomes an extremely important factor in terms of health and well-being.

UNE 171330:2008 defines Indoor Environmental Quality as the environmental conditions of an enclosed space suitable for the user and the activity performed, defined by the levels of chemical and microbiological contamination and by the values of physical factors. [3]

Temperature, humidity, electroclimate, and air quality are factors that influence the environmental quality of a space, with the latter being one of the most important.

In accordance with these data, the standard (UNE 171330:2008) focuses on measuring the values of harmful agents that deteriorate air quality. Among the most common are carbon monoxide (CO), sulfur dioxide (SO2), suspended particles, asbestos, ozone, fungi and bacteria, household products, nitrogen oxides (NOx), radon, and volatile organic compounds (VOCs).

Volatile organic compounds are a group of toxic components that significantly contribute to the deterioration of air quality. New building regulations that tend towards airtight spaces and the pressure from developers and builders to progressively reduce construction costs and times lead to the use of synthetic, highly processed materials that incorporate a high amount of chemicals in their manufacturing processes. All of this has resulted in elevated concentrations of VOCs in indoor spaces.

The most common sources of these pollutants are combustion products, construction and decoration materials, and products used in daily activities such as cleaning. Therefore, these types of components are continuously present in people’s lives, negatively affecting their health.

High concentrations of VOCs can impact people’s health in the short and long term, causing everything from irritations or allergic reactions to serious disorders and injuries such as Multiple Chemical Sensitivity syndrome. [4]

Furthermore, VOCs also have adverse environmental effects as they contribute to altering the distribution and levels of ozone — a gas that acts as an air purifier and UV filter — affecting the Earth’s atmosphere by promoting global warming.

To ensure healthy construction free of volatile organic compounds, we must first understand exactly what they are, their families, and their origin. In addition to being aware of their negative effects on people’s lives and the planet.

Secondly, there is existing legislation regarding VOCs, so we must be aware of regulations concerning the concentrations of volatile organic compounds, which can help provide a notion for toxic-free construction.

Finally, understanding exactly what the sources of VOC emissions in construction are and how we can distinguish them through ecological certifications can promote healthier construction for people and a less aggressive approach to the environment.

WHAT ARE VOCs?

Definition of VOC

Volatile Organic Compounds are chemical substances that, as their name suggests, are characterized by having a carbon chemical base (a constant component of organic substances) and by their high volatility. That is, they are substances that are present in a gaseous state in the environment, or, if they are in a liquid state, they tend to evaporate at room temperature.

Organic compounds can be classified by their boiling point, and those with a boiling temperature between 50 °C and 260 °C are considered volatile.

In addition, based on the boiling temperature, the WHO has established three other categories:

If the boiling point is lower than the above, between 0 °C and 100 °C, they are called very volatile (VVOCs); if it is higher, between 240 and 400 °C, they are considered semi-volatile (SVOCs); and finally, if it is even higher, they are classified as particle-associated organic compounds (POAOCs).

Composition of VOCs

VOCs are usually formed by a chain of atoms with fewer than twelve carbons, combined with atoms of other elements such as oxygen, fluorine, chlorine, bromine, sulfur, nitrogen, or hydrogen. [5]

VOC Families

The term VOC groups a large number of types of chemical compounds, which can be grouped into families according to their composition. [6]

– Hydrocarbons, among which alkanes, alkenes, and aromatics stand out.

– Acetates / aldehydes such as formaldehyde, acetaldehyde, acrolein.

– Ketones such as acetone.

– Free acids such as formic acid and acetic acid.

– Alcohols such as methanol.

– Ethers and esters.

– Terpenes.

The hydrocarbon family, i.e., organic compounds formed from carbon and hydrogen, is the most abundant. Some of the gases resulting from these combinations are methane, toluene, n-butane, i-pentane, ethane, benzene, n-pentane, propane, and ethylene.

Among the gases mentioned above, it is worth noting that some are characterized as extremely dangerous to health, such as benzene. While others, like methane, can cause significant environmental impacts, as they contribute to the destruction of the ozone layer.

Origins of VOCs

Volatile organic compounds can have a biogenic (natural) or anthropogenic (human) origin. Naturally occurring VOCs would be those released by plants, while human-origin VOCs are all those resulting from industrial and vehicular activities.

On a global scale, VOC emissions originating from vegetation, such as deciduous species which are the main emitters of hydrocarbons, represent more than 87% of total atmospheric emissions. However, these biogenic emissions are dispersed over larger areas, unlike anthropogenic emissions which are concentrated in industrial and urban areas, which is why they have a greater impact on health. [7]

Industrial activities such as fuel combustion (gasoline, wood, coal, or natural gas) and vehicle use account for a large part of anthropogenic VOC emissions into outdoor air. However, the presence of VOCs in indoor air is also high. New constructions and recently renovated buildings include products such as resins, varnishes, paints, solvents, furniture treatment products, carpets, rugs, and others commonly used that, due to their composition, emit organic compounds that volatilize into the indoor air of homes and workplaces. [8]

EFFECTS OF VOCS ON HEALTH

The presence of volatile organic compounds worsens both outdoor and indoor air quality. However, according to research by the U.S. Environmental Protection Agency, levels of a dozen common organic pollutants are two to five times higher indoors than outdoors, regardless of whether the buildings are in rural or urban areas.

In this sense, constant exposure to VOCs in indoor environments represents a real and harmful risk to people’s health and well-being. Moreover, according to the WHO, poor indoor air quality accounts for 4.1% of all global deaths. [9]

On the other hand, they are also outdoor air pollutants as they are ozone depleters and precursors of ground-level ozone. In combination with certain climatic circumstances and specific pollutants, they give rise to atmospheric pollution known as “smog” (from smoke and fog) [10]. Consequently, it can be said that they not only create problems by directly attacking the ozone layer but also act indirectly as secondary pollutants.

Effects of VOCs on human health

As mentioned, the main effect of the presence of volatile organic compounds in indoor environments is the contamination of the air breathed by the people occupying that space. Indoor air pollution contributes to Sick Building Syndrome, which, according to the WHO, affects between 10% and 30% of occupants in 30% of current buildings.

The damage can vary depending on the nature of each compound and the degree and period of exposure. Likewise, they can vary at both physical and cognitive levels.

Short-term exposure can have the following consequences [10,12,13]:

– Eye and respiratory tract irritation

– Headache

– Dizziness

– Visual disturbances

– Fatigue

– Loss of coordination

– Allergic skin reactions

– Nausea

– Memory disorders

While long-term exposure can have much more severe repercussions on people’s bodies, even causing [10,12,13]:

– Liver and kidney damage

– Alterations in the central nervous system

Furthermore, studies conducted by the International Agency for Research on Cancer (IARC) classify some VOCs, such as formaldehyde, as carcinogens. [14] In addition, some others, such as benzene and butadiene, are considered leukemia-inducing agents (WHO, 2000).

Effects of VOCs on the environment

On the other hand, the study of VOCs is of particular importance because these pollutants play a significant role in many current environmental problems [10].

– Stratospheric ozone depletion.

Many VOCs release compounds that trigger the destruction of the stratospheric ozone layer.

– Tropospheric ozone formation.

The reaction of VOCs with other pollutants, nitrogen oxides, and sunlight results in tropospheric ozone, i.e., ground-level ozone. This leads to the previously mentioned phenomenon known as smog. There are two types of smog: industrial, caused by the burning of large quantities of fuel in industries and appearing as a gray fog, and photochemical, caused by reactions between sunlight and nitrogen oxides and appearing as a reddish fog.

– Enhancement of the global greenhouse effect.

The planet, which is heated by a portion of solar radiation, emits infrared radiation, which is long-wavelength radiation not part of the visible spectrum. These infrared radiations are characterized by their thermal effects, and thanks to greenhouse gases, they are re-emitted to the surface, resulting in a warm atmosphere with a suitable temperature for human life.

However, the problem arises when, due to anthropogenic reasons, there is an accumulation of greenhouse gases on the surface, for example, VOCs, which have the capacity to absorb part of the infrared radiation and, therefore, enhance the greenhouse effect and cause overheating of the atmosphere.

There are other volatile organic compounds that do not have this absorption capacity, although they can still modify the global distributions of other gases that do.

– Accumulation and persistence in the environment.

Some compounds with very high molecular weight eventually become persistent, thus contributing to the three phenomena mentioned: the enhancement of the global greenhouse effect, the formation of tropospheric ozone, and the destruction of stratospheric ozone.

CURRENT LEGISLATION REGARDING VOCs

Environmental legislation has developed in the same direction, but in two ways. On the one hand, it has been established around Green Chemistry, and on the other hand, it has focused on waste disposal once already produced.

Green Chemistry emerged from the concept of Sustainable Development, understood as a way to progress without harming the health of the planet or future generations. Thus, its main objective is to develop new or improve existing chemical products and processes to reduce the danger to human health and the environment. In other words, it seeks to eliminate the problem at its root.

However, most of the existing regulations regarding environmental quality are oriented in the second sense. Nevertheless, it should be noted that there is a certain absence of regulation specifically concerning indoor air quality in residential, educational, or healthcare buildings. Consequently, this exacerbates the situation and poses a greater risk to the people occupying those spaces.

Regulations only cover part of the problem by limiting emissions from some products or activities, setting minimum ventilation rates, and establishing exposure limit values exclusively for some of these substances and in specific areas. Furthermore, compliance with the limit values established by European Air Quality Directives or the CTE does not guarantee people’s health, as they are often less stringent than the values set by the WHO in its air quality guidelines. [15]

– Regulations concerning the limitation of VOC emissions at European and Spanish levels

Given the significant influence of volatile organic compounds on people’s lives and the environment, on March 11, 1999, the Council of the European Union approved the first regulation concerning the limitation of VOC emissions due to the use of organic solvents in certain activities and installations.

Directive 1999/13/EC [16] aimed to prevent or reduce the direct or indirect effects of volatile organic compound emissions on the environment, mainly the atmosphere, and the potential risks to human health.

In Spain, this directive was transposed by the Ministry of Environment as Royal Decree 117/2003 [17], of January 31, 2003. This decree sets out the obligations applicable to existing installations and requirements for new ones.

– Later, on April 21, 2004, Directive 2004/42/EC [18] of the European Parliament and of the Council was approved, concerning the limitation of VOC emissions due to the use of organic solvents in certain paints and varnishes and in vehicle refinishing products. This constituted an amendment to the 1999 Directive and its transposition at the Spanish level through Royal Decree 227/2006 [19], of February 24, 2006. This decree implements a series of mandatory requirements for the marketing of products that emit organic compounds, as well as limiting the maximum VOC content in their composition. Furthermore, it imposes the obligation to include a label indicating the product type and the maximum VOC content.

The aforementioned regulations are of great technical complexity, although, ultimately, the main objective is to regulate and control VOC emissions from products that generate the most emissions and are most widely used (e.g., solvents) in order to improve environmental and human quality of life. To this end, they establish compliance with certain obligations for both new and existing installations. They also set emission limit values and guidelines for measuring volatile organic compounds.

On the other hand, in the same vein against pollution, a group emerged in Spain within the Ministry of Environment with the objective of developing “The Spanish Thematic Strategy for Air Quality,” which consisted of developing an integrated long-term strategy to protect human health and the environment from the effects of air pollution. Among the program’s priorities, two aspects stood out: particles with a diameter smaller than 2.5 microns and the limit values for nitrogen oxides (NOx) and volatile organic compounds (VOCs). [10]

The objective materialized with the REACH Regulation (Regulation for the Registration, Evaluation, Authorization and Restriction of Chemicals). The regulation proposed that each chemical industry had to carry out tests and risk assessments for all substances produced and imported, an essential fact to prevent risks and manage polluting waste. [10,20]

Recently, the Strategic Health and Environment Plan 2022-2026 [21] has also been published, which aims to address the most relevant environmental risk factors and delves into their impact on health. Thus, the Plan includes, in the thematic areas of Industrial Pollution and Indoor Environmental Quality, points specifically dedicated to the study of VOCs in industrial pollutants and in household products and solvents. [21]

VOC Concentrations

In general, in developed countries, higher VOC concentrations are logically observed due to a greater presence of industry, vehicles, and construction.

In Spain, the main problems are similar to other European countries, and the areas with the highest levels of pollution are specific industrial areas and, especially, large cities where vehicle traffic emissions are the main contributors to VOC emissions.

Temperature, humidity, ventilation, and the type of activity carried out also influence VOC concentrations.

VOC Limits

The limits established by regulations, as mentioned, refer to very specific situations or products. Furthermore, they depend on each specific compound. Thus, no general limitation has been established that can be widely applied.

A specific case is presented by Directive 2004/42/EC, which imposes a maximum VOC concentration value in paints and varnishes ranging between 30 and 750g/l depending on the type of finish, and requires its labeling. [15]

VOC-FREE CONSTRUCTION

Healthy construction is about contaminant-free construction, where indoor air quality is high and not a risk factor for users. Likewise, construction must be VOC-free.

Therefore, we must first consider what the main anthropogenic emission sources are, as these are the most influential in construction.

Secondly, keeping these emission sources in mind, the emissions generated by a product can be determined through Safety Data Sheets, which have been mandatory since the European regulation established in 2006.

However, these sheets only need to include the presence of substances whose concentration exceeds the established legal limits, which is why manufacturers are increasingly providing consumers with a complete Declaration of Components. These are known as Environmental Product Declarations, EPDs (Environmental Product Declaration), and if a product were related to VOC emissions, these declarations should include information about it.

DAP

An Environmental Product Declaration [22] is a type of document that does not establish preferences or minimum requirements; it simply provides transparent information on objective, comparable, and third-party verified data regarding the environmental performance of products from a life cycle perspective (LCA).

EPDs are considered non-mandatory eco-labels that consist of a product description including technical data and an analysis with its respective results of the life cycle stages; that is, from product manufacturing, to construction and use, up to waste management.

Every Environmental Product Declaration is adapted and analyzes the most relevant factors of the product in question in each case. Although all are developed following a methodology regulated by standard EN 15804 and ISO standards (ISO 14025, ISO 21930, ISO 15804). Thus, there are parameters and indicators around which they are developed.

The environmental impact indicators considered in an EPD analysis are:

– Global Warming Potential (GWP)

– Acidification Potential (AP)

– Eutrophication Potential (EP)

– Photochemical Ozone Creation Potential (POCP)

– Ozone Depletion Potential (ODP)

In this sense, it can be seen that one of the key factors on which EPDs are based, specifically photochemical ozone formation, is directly related to the effects of volatile organic compounds in the air. Thus, it is common to find information on VOCs, as they are part of the same unit of measurement used for this indicator.

Furthermore, in cases where VOCs are known to play an important role, such as with interior paints, in addition to the POCP meter, specific information on VOC content can also be found.

In parallel, there are many other types of building certifications, such as LEED or the WELL Standard in the United States, BREEM in England, or VERDE in Spain, which include specific points regarding indoor air quality. However, such certificates only generally cover the presence of VOCs and at the general building level.

Sources of VOCs in construction

In urban environments, VOC emissions are primarily anthropogenic and consist of a complex mixture of traffic residues, industrial emissions, solvents, waste combustion, and other sources, such as construction materials. However, VOCs emitted by plants and trees also contribute to the urban VOC mixture. Nevertheless, the atmospheric lifetime of the latter is much shorter, so their impact is also smaller. [12]

In recent decades, VOC emissions from traffic had the greatest impact due to the large quantities of compounds they emitted. However, these have significantly decreased in many cities thanks to catalytic converter technology and the replacement of diesel fuel with cleaner fuels such as liquefied petroleum gas (LPG) or compressed natural gas (CNG), or alternatives that do not contain fossil fuels, such as electric power. [23]

Consequently, other sources of VOCs are emerging with relative importance. In fact, it is currently estimated that chemical products, which can include varnishes and paints, account for half of VOC emissions in Europe and the United States of America.

For this reason, it is increasingly important to consider VOC-emitting agents other than vehicles, and to cover fields such as VOCs in construction.

Sources of VOC emissions in outdoor spaces

VOC emissions originating from construction in outdoor spaces are mainly due to raw material extraction and manufacturing processes (construction industries), activities carried out by workers on site using various products, and asphalt paving.

In the first case, it is an industrial activity, so fuels are used whose combustion can lead to VOC emissions. These are point emissions, making them easily controllable and measurable.

Furthermore, during construction work, VOCs may also be present. Spraying paint or using solvents during the construction process exposes workers to volatile organic compounds while also becoming a source of outdoor air emissions. [24]

Another notable source is the construction of roads, highways, parking lots, or other pavement repairs. The installation of asphalt pavement emits a large amount of fumes containing volatile organic compounds, which can cause potential health risks for workers in addition to having a significant environmental impact. [25]

However, in terms of construction, the most common types of emissions that have the greatest impact on people’s health are those that occur in the indoor environment.

Sources of VOC emissions in indoor environments

VOC emissions in indoor environments are due to the use of a wide range of products such as wood elements, decorative materials, paints, varnishes, glues, or other material maintenance or furniture products. Even some cleaning products can contain these types of compounds. [10]

Below, according to the type of product, the possible VOCs they can emit are identified.

Wood-based materials

Among the materials that can be most dangerous in relation to VOC emissions into the environment, the following stand out:

– Pressed wood (particleboard and plywood).

– Wood panels.

Particleboard is made from fine wood particles mixed with UF resins and pressed into wood panels. Formaldehyde is trapped as a residue in the resin manufacturing process.

Thus, during the first months of installing floors, wall panels, shelves, and cabinet and furniture pieces made from particleboard, formaldehyde emissions occur. As the life cycle of these products progresses, emissions decrease.

To address this situation, particleboards that use formaldehyde-containing resins can be replaced by others mixed with adhesives, as they show significantly lower formaldehyde emission potentials. In addition, environmentally friendly adhesives using natural tannin instead of adhesives have been developed, thus reducing reliance on formaldehydes.

Flooring materials

– Carpets

– Parquet

– Laminate

– PVC

– Rubber

Carpets can be major sources of aromatic and aliphatic hydrocarbons. Parquet and laminate flooring cause formaldehyde emissions due to the presence of adhesives and glues in their composition. On the other hand, the use of PVC is discouraged due to the possible acetate emissions it can cause.

However, for flooring, linoleum can be used, a material that serves as a natural replacement for wood or other VOC-emitting products, as, although it is also associated with VOC concentrations, it is to a much lesser extent. Comparing the VOC concentrations associated with linoleum, they are observed to be much lower (5.19 mg/m³) compared to those associated with PVC (54.80 mg/m³).

Insulation materials

Some of the insulations with the highest VOC emissions are:

– Rock wool

– Glass wool

Rock wool is mainly composed of an inorganic content of glass, stone, or slag; however, the remaining content consists of thermosetting resins. The same applies to glass wool, where, although its main component is an inorganic material, the remaining percentage consists of resins. These resins contain formaldehyde, which leads to emissions of this compound during use.

While it is true that emissions produced by rock or glass wool are much lower than those produced by formaldehyde-based foams, which were used previously and are no longer relevant today.

Coatings

Regarding coatings, the variety of organic compounds they can release is very extensive.

– Paints

– Plastics

– Gypsum boards

– Vinyls and wallpapers

– Textiles

– Ceramic coatings

Paints can be sources of aromatic or chlorinated hydrocarbons, acetates, ethers, esters, and terpenes. However, it is important to highlight water-based latex paints as they are associated with high formaldehyde emissions.

Plastic coatings add alcohol emissions to the list. Similarly, gypsum boards add aliphatic hydrocarbon emissions.

On the other hand, vinyls and wallpapers can also lead to VOC emissions due to their installation, which involves the use of glues and adhesives.

Likewise, some textiles are treated with formaldehyde resins, leading to significant emissions of this compound. Therefore, if textiles are used, it is preferable that they be natural.

Furniture

– Wood products

– Upholstery and curtains

– Carpets

The majority of furniture in our homes is made of wood, so it is important to note that if it is particleboard or plywood, the VOC emissions from that piece of furniture will be significant.

Regarding other furniture pieces such as upholstery, curtains, or carpets, they may be composed of textiles that include organic compounds, so caution is advisable, as otherwise, hydrocarbon or acetate emissions could occur.

Wood products

– Varnishes

– Wood stains and treatments

– Waxes

All products related to wood care, such as varnishes, waxes, treatments, or stains, include volatile organic compounds in their composition that can cause VOC emissions (such as hydrocarbons, chlorinated compounds, ethers and esters, and terpenes) during their use.

Household consumer products

– Cleaning products

– Adhesives

– Solvents

– Metal cleaners

– Anti-mite products

– Fungicides

Finally, there are cleaning products, adhesives, anti-mite products, and fungicides whose composition includes compounds that can lead to emissions of hydrocarbons, alcohols, ethers, and esters.

Healthy construction

Continuing with VOC-free construction, we must first utilize materials associated with lower VOC emissions. Meanwhile, we can also employ certain methods to reduce VOC concentrations.

VOC-free materials

Referring to the previously mentioned documents, known as EPDs, can help identify whether a material is VOC-free. However, if this is not the case, it is possible to prevent volatile organic compound emissions by avoiding the materials explained in the previous section.

For example, prioritizing the use of linoleum or other low-emission flooring instead of PVC flooring or carpets can provide the interior air of the home with better qualities.

Furthermore, in the case of varnishes, it is preferable to use medium-solid and traditional ones as they are less emissive. Alternatively, in the case of solvents, use those with slow evaporation. [27]

Application conditions

Another aspect to consider in construction is the application environment for products containing VOCs.

Temperature significantly influences the moment of application. It is recommended to maintain an application temperature between 18 and 22°C. Higher temperatures favor product evaporation and consequently increase the amount of VOCs in the environment. [27]

Biofiltration

Biofiltration is a relatively recent air pollution control technology. It is a system through which volatile organic compounds—or other environmental toxins—are ventilated through a biologically active material.

This technology has achieved control efficiencies for many pollutants of over 90% in countries such as Germany or the Netherlands, where it has been used to control emissions of VOCs and toxic substances into the air. [28]

Applying the biofiltration method can not only yield environmental benefits but, due to the lower operating costs of this technology, can also provide economic advantages over other technologies.