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Jun 10, 2013

Port Townsend Paper Mill. Why are you Risking your Health? Pulp and paper mills use a variety of chemical substances potentially hazardous to human health. Is it worth the RISK to continue breathing TOXIC air? Is the Port Townsend air toxic? Or is that Odor a HARMLESS smell of "Money". Try money for the Heart Doctor, Lung Doctor, Cancer Treatment, Chronic Pain, and medical bills.

"Which studies do you believe? What are you willing to risk?

"Pulp and paper mills use a variety of chemical substances potentially hazardous to human health. 

Compounds of both short- and long-term toxicological significance are found in workplaces, air emissions, and water effluent.

In this paper we evaluate the body of published literature on cancer associated with working in pulp and paper mills as well as in surrounding communities.

Multiple comparisons, questionable statistical power, and the absence of individual exposure assessments have resulted in non-corroborative findings over the years.

However, a new generation of study sophistication, international in scale and coordinated by the International Agency for Research on Cancer (IARC), has catalogued tens of thousands of exposure measurements made at a large number of work stations within the pulp and paper industry, allowing for greatly improved individual-level exposure assessments.

This approach reduces non-differential misclassification of exposure, increasing the power of these studies to detect exposure disease relationships, especially for rarer cancers.
While the ability to associate specific chemical exposures with cancer outcomes in the large IARC multinational cohort may yet help to resolve the status of some of the many chemicals not currently classifiable as to their carcinogenicity by IARC, this effort has, to date, not added significantly to knowledge. Of the three studies they have published to date, one involved a well-established carcinogen (asbestos) and another involved a mixture containing probable carcinogens (volatile organochlorines). While the asbestos study is somewhat unremarkable for finding an association with pleural cancer in the expected direction, the volatile organochlorine study may be most notable for failing to find an association between volatile organochlorine exposure and liver cancer, non-Hodgkin’s lymphoma, or esophageal cancer, as some previous studies had found.
Nonetheless, given the known hazards and the potential for both environmental and human exposure by any of a number of pathways, vigilance on the part of governments for regulation and for ongoing workplace and environmental monitoring remains a health imperative.

Introduction

The importance of the pulp and paper industry in modern life is a result of the major role of paper and paper products in every area of human activity. However, like many industrial processes it has impacted our environment and our health. Health concerns include both occupational hazards and impacts on air, soil, and water that affect the health of communities in the vicinity of pulp and paper mills as well as of those communities downwind or downstream from mills.
In this paper, we provide some background on the pulp and paper industry, then review both the English-language published literature and accessible unpublished reports of the epidemiological and toxicological evidence relating to the contribution of the pulp and paper industry to cancer risk. The focus is on studies of cancer risk associated with having worked in the pulp and paper industry. In addition, we have reviewed what information is available on the effects of these industries on cancer risk in local communities.
Health implications of work in the pulp and paper industry were reviewed at the global level in 1998 in the International Labour Organization’s Encyclopaedia of Occupational Health and Safety, prior to the current crop of studies.1-5 In sum, workers have been exposed to mechanical and chemical pulping processes, the latter mainly split between kraft (or sulphate) and sulphite processes. Local community exposures include chlorinated organic compounds, polychlorinated dibenzodioxins, and polychlorinated dibenzofurans. In addition, respirable particles of lime and sulphates have been found in the ambient air surrounding pulp mills.
The chemicals used and produced by pulp and paper mills vary according to a number of factors, including the wood species, pulping processes, and bleaching processes used.
It should be noted that some of the chemicals to which workers have been exposed have been reduced or eliminated in recent years. Asbestos is an example of a substance that workers were exposed to in the past, but which is now largely eliminated in the developed world. Mill effluent has also been cleaned up in recent years. In Canada, strict new regulations on mill effluent came into effect in 1992, with subsequent reductions in environmental discharges.6 However, cancer has a long latent period, so all of the exposures in the past century of pulp and paper making are of interest.

The production context

The component of interest in the manufacture of pulp and paper is cellulose. Cellulose is a long-chain carbohydrate composed of polymerized glucose. It forms strong fibres that are ideal for paper-making. To obtain the cellulose fibres, short-chain carbohydrates called hemicelluloses (which are combinations of sugars including glucose, mannose, galactose, xylose, and arabinose) must be removed. Compared to cellulose, the hemicelluloses are easily degraded and dissolved.
Woody plant materials also contain an amorphous, highly polymerized substance called lignin that forms an outer layer around the fibres and cements them together. Lignin is also contained within the fibre. The chemistry of lignin is complex. It consists primarily of phenyl propane units linked together in a three-dimensional structure. The linkages between the propane side chains and the benzene rings are broken during chemical pulping to release cellulose fibres. A number of additional substances (e.g., resin acids, fatty acids, turpenoid compounds, and alcohols) are present in native fibres, their exact constituents and proportions depending upon their plant source. Most of these compounds are soluble in water or in neutral solvents, and are collectively called extractives.
Pulp mills extract and process cellulose fibres from wood, simultaneously removing unwanted constituents, such as lignin. The two main types of pulping processes are mechanical and chemical. Mechanical pulping uses heat and mechanical forces to separate the wood fibres into a light-coloured pulp that requires little bleaching. Chemical pulping uses a mixture of chemicals to separate the cellulose fibres from the lignin. The two major chemical pulping processes are kraft (or sulphate) and sulphite.
Figure 1 is a simplified process diagram for a kraft mill. Kraft pulping is carried out in an alkaline medium and releases fibres from wood chips by dissolving the lignin in a caustic solution of sodium hydroxide and sodium sulphide. 
Spent digester fluid is concentrated in evaporators and fed into the recovery furnace, which recycles solid sodium sulphide and combusts the organic component as a source of energy.

A lime kiln recovers calcium oxide for regeneration of the caustic component of the digester fluid.
Figure 1
Simplified diagram of the kraft pulping process
In contrast, the sulphite process is carried out under acidic conditions and solubilizes lignin through sulfonation using a solution of sulphur dioxide and alkaline oxides such as sodium, magnesium, ammonium or calcium. The recovery of digester fluid components is accomplished by various means depending on the alkaline oxide used.

Both chemical processes produce a relatively dark-coloured pulp that requires bleaching. The vast majority of the 47 bleached pulp mills operating in Canada through 1993 used the kraft method.7 Five mills employed the sulphite process.
The resulting pulp is washed and bleached – in the past with elemental chlorine, today with chlorine dioxide and/or hydrogen peroxide. The washed pulp is rolled and dried, and the dried pulp is cut and baled for shipment. Several decades ago, wastewater from the bleaching process was typically discharged directly into a nearby body of water.

Since about the 1960s, mills were required to perform primary treatment of effluent (i.e., settling out of large particulates before discharge). Today, however, Canadian mills are required by federal regulations to perform secondary treatment in addition. Most mills in Canada use aerated stabilization basins or activated sludge to remove oxygen-consuming materials and decrease the effluent toxicity, and this toxicity is monitored.8a

Variations in wood species

Moving across Canada geographically from west to east, there are four major forest land formations: the Pacific Coastal Complex, the Rocky Mountain Complex, the Boreal Forests, and the Eastern Deciduous Forests. Depending on the raw material (i.e., tree species) used in pulp and paper production, different environmental and occupational exposures will result.
Botanically, woods are classified into two main groups: the gymnosperms are the softwoods, conifers or evergreens; the angiosperms are the hardwoods – either deciduous or broad-leaved trees. The different wood species used in pulping require different types and quantities of chemicals, different in-plant processes and result in different by-products and product properties.
Generally, hardwoods contain a larger proportion of cellulose and hemicellulose and less lignin, as compared to softwoods, but a greater percentage of extractives. In addition, hardwood effluent contains chlorinated syringols. In general, softwood produces greater quantities of phenolic compounds than hardwood. Softwood effluent, chlorinated in the bleaching process, contains chlorophenols, chloroguaiacols and chlorovanillins.

Epidemiological studies of pulp and paper mill workers

Exposure of pulp and paper mill workers to potentially hazardous materials may arise at any stage in the process, from preparation of the raw wood through the production of the final pulp or paper product (Table 1). Wood preparation does not differ substantially for the several processes, but there can be significant differences in exposures in subsequent process steps, including cooking liquor production, pulp production, washing, bleaching, recovery, and paper making.
Most exposure studies in pulp and paper-making are of gaseous sulphur compounds, chlorine and chlorine dioxide. Though they have been shown to have significant respiratory and cardiovascular effects, these sulphur compounds have not been shown to be carcinogenic. In addition, vapours emanating from pulp may contain terpenes, sodium hydroxide mist, methanol, ethanol, sulphuric acid, furfural, hydroxymethylfurfural, acetic acid, formic acid, gluconic acid, hydrogen peroxide and many other potentially hazardous compounds. Dusts consisting of lime and sodium sulphate (among others) are also present and pose a potential exposure risk during the chemical recovery process.9 Long-term exposure to fine particulate matter (PM2.5) such as this is thought to cause lung cancer.10 Pesticides used for control of slime and algae also constitute potentially harmful exposures. Exposure to complex chlorinated organic compounds, some of which are probable carcinogens, may occur through contact with slimicides (e.g., pentachlorophenol), pesticide-treated wood, or compounds formed during the bleaching process. Welders are exposed to hexavalent chromium in stainless steel welding. Perhaps most importantly from a cancer risk perspective, in the past workers (especially maintenance workers) were commonly exposed to asbestos.
Table 1
Occupational exposures in the pulp and paper industry
Production area/jobPotential exposures
Raw wood preparation (i.e., debarking, chipping)Wood volatiles, wood dust, spores, fungi, microbes
Production of cooking liquorSulphate: ammonia, hydrogen sulphide, sulphur dioxide, mercaptan, chromate and other contaminants
Sulphite: sulphur, sulphur dioxide, calcium carbonate, zinc, sulphuric acid, lead fumes, asbestos, sulphurous acid
Pulp production, cookingSulphate: lime, magnesium, wood volatiles
Sulphite: pigments, dyes, wood volatiles
Ground wood: wood volatiles, aniline
Pulp bleaching, bleach plantChlorine compounds, ozone, hydrogen peroxide, boron compounds, caustic acids
Wet pulp, paper additivesTalc, clays, titanium dioxide, urea and melamine formaldehyde, pigments, dyes
Paper rolling, sizing, dying, drying, glazing, coatingUrea and melamine formaldehyde, paper dust, coating and pigment dusts
MaintenanceGeneral plant exposures, asbestos, welding fumes
Unknown jobs, power, utilityGeneral plant exposures, asbestos
Unexposed jobsNo significant exposures
Important challenges in occupational cancer studies
Workers represent a well-defined group of people for epidemiological assessment. The occupational health status of pulp and paper mill workers has been studied for a variety of endpoints, including cancer, pulmonary function, skin diseases, and hearing impairment. For some endpoints, such as cancer and respiratory effects, findings have varied considerably across studies.
Exposure assessment has been a significant issue in past studies. Lacking measurement of exposure to specific chemicals, most cohort studies have divided workers into at least three exposure categories: those who work in a paper mill, a sulphate (kraft) pulp mill, or a sulphite pulp mill. For simplicity, workers usually are categorized according to the last job they held, and exposure is defined as duration of employment. This surrogate exposure assessment is crude and may be problematic if the person has performed different jobs over his or her lifetime. Inadequate exposure assessment and other methodological problems in the generation of studies prior to about the mid-1990s, have resulted in controversy over their interpretation.
Efforts are being made to improve exposure assessment,11-15 which would permit more valid classification of workers for study purposes. Of particular note is the more recent large international effort to take new, detailed measurements of specific chemicals across the spectrum of jobs in the pulp and paper industry, and to integrate them with all known previous measurements dating back to the 1950s.13-15 Such detailed measurements have yielded more comprehensive job-exposure matrices and more accurate and specific exposure assessments.
In addition to the ongoing challenge of exposure assessment, there is another significant and related challenge that will become obvious in our review of the occupational cohort studies in the pulp and paper industry: choosing an appropriate comparison group. Most of the cohort studies that we have reviewed report the standardized mortality (or incidence) ratio (SMR or SIR) as their measure of effect. These measures compare mortality rates (or disease incidence) in the study cohort to the general population while simultaneously accounting for discrepancies in the age distribution of the two groups. The SMR and SIR have a number of advantages and disadvantages, but the chief disadvantage in the studies we review is its susceptibility to the healthy worker effect.
The healthy worker effect (HWE) is a form of bias caused by the fact that people who become sick or are especially sensitive to exposures in a particular workplace are not likely to start or continue employment at that workplace. Thus, occupational cohorts tend to be made up of quite healthy or resistant individuals compared to the general population. Especially when studying relatively subtle associations, the difference in the general robustness of the workforce compared to the general population can make it difficult to detect the effect of toxic exposures on health. Indeed, in a review of 270 occupational cohort studies, Meijers et al.16 found that most exhibited a HWE (mean SMR: 84) which had a large influence on the study findings, tending to turn what might have been statistically significant positive findings into negative or equivocal findings. The effect was especially prominent among those studies involving chemical exposures. Unfortunately, the HWE is difficult to control and is not easily distinguished from other possible explanations (like genuine protective effects). Arrighi and Hertz-Picciotto17 have reviewed methods for avoiding or correcting for the HWE, but these methods were not used in the older studies we review below. Some of the newer studies have avoided the problem by choosing a non-exposed group of workers (e.g., administrative office workers), rather than the general population, as the comparison group.
Another methodological challenge that arises frequently in occupational cancer studies is the problem of multiple comparisons. It is not uncommon for investigators to search for excess risks among up to 30 different cancer sites, frequently over three or more exposure categories and two or more latency periods. Thus, many papers essentially involve a search for statistical significance across 200 or more comparisons. Yet, although one would expect as many as ten statistically significant results to occur by chance alone (at the 95% level of significance), almost never is a statistical or interpretive adjustment made for this problem.
Case-control and proportional mortality studies
Thirty-two case-control and proportional mortality studies have presented some data on cancer risk among pulp and paper workers.18a-49 Occupation was usually abstracted from death certificates or from cancer registries. The occupational groups in most of these studies were broad.
The case-control and proportional mortality studies revealed few statistically significant associations between cancer and working in the pulp and paper industry. The case-control studies were generally much weaker than the cohort studies reviewed below, largely because most did not attempt detailed exposure assessment. Most of the studies referred only to the pulp and paper industry in general, or to production versus non-production workers, and did not separate the workers by process. This is problematic because the exposures are quite variable among the different processes.
Lung and pleural cancers have been of significant interest to researchers of pulp and paper workers. In a study designed to avoid the healthy-worker bias, Menck and Henderson found a significantly increased risk of lung cancer among paper workers (SMR= 171, where the denominator included only working people).31 
In a relatively weak study design, Harrington et al. found a statistically elevated risk of lung cancer (OR = 3.3) in non-urban counties where pulp and paper was the major industry.28 In a death certificate analysis of counties in Louisiana, Gottlieb et al. found no increased risk of lung cancer among either pulp and paper workers or residents living near pulp and paper mills.26"
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