Incidence of amyotrophic lateral sclerosis in the province of Novara, Italy, and
possible role of environmental pollution.
Marina Tesauro
1, Michela Consonni
1, Tommaso Filippini
2, Letizia Mazzini, Fabrizio
Pisano, Adriano Chiò, Aniello Esposito and Marco Vinceti
2Affiliations:
1* Dipartimento di Scienze biomediche chirurgiche odontoiatriche, Università degli Studi di Milano
2** Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Università degli Studi di Modena e Reggio Emilia
^ Clinica Neurologica, AOU Maggiore della Carità, Novara
^^ Divisione di Neurologia Riabilitativa, Fondazione Salvatore Maugeri, Veruno
# Dipartimento di Neuroscienze ‘Rita Levi Montalcini’, AOU Città della Salute e della Scienza, Torino
## Servizio Igiene e Sanità pubblica- ASL Novara
Introduction
Amyotrophic lateral sclerosis (ALS) is an adult-onset, fatal disorder, characterized by degeneration of both upper and lower moto neurons. Clinical presentation of ALS includes muscle atrophy and weakness. Subsequently, spreading paralysis of the voluntary muscles often develops, and eventually of the respiratory muscles. Approximately half of patients with ALS die within 30 months from symptoms onset, usually from respiratory insufficiency, whereas about 10% of patients may survive for more than a decade (1-5). About 5-10% of ALS patients have a familial form (6). If no family history is identified, the diagnosis is assumed to be sporadic.
Worldwide, ALS incidence ranged from 2 to 4/100.000 people per year with the exception of some high-risk areas around the Pacific Rim such as Guam or parts of Western New Guinea (7). In Europe, the median annual incidence rate is 2.08/100 000 population (Interquartile Range - IQR 1.47-2.43), while the median prevalence is 5.40/100 000 population (IQR 4.06-7.89)(8).
The etiology of ALS is still unknown. Genetic factors play a major role in the familial form (9, 10), while for the etiology of the sporadic form several environmental and life-style factors might be involved, such as heavy metals (particularly lead, mercury) and the metalloid selenium (11-20), solvents (21, 22), pesticides (23-27), electric shocks and electromagnetic fields (28, 29), smoking, severe head trauma and intense sport activity (30-33).
Generally, ALS is rare before the age of 40 years, thereafter it increases exponentially with age with a peak incidence in those aged 70-79 years; male to female ratio ranges from 1.2 to 1.5 (34). Mean age at onset range from 58 to 63 years for sporadic form and 40 to 60 years for familial form (35-41).
During recent decades, an increasing mortality or incidence of ALS has been reported, especially in Sweden, Finland, Norway, France, the USA, although this increase is less evident in some country (42-59). In addition, there is evidence for an uneven distribution of the disease in several countries, suggesting a potential role of environmental factors. In Italy, a study describing the distribution of ALS mortality in the period 1980-2001 has detected 16 single clusters, i.e.
municipalities with higher mortality rates for motor neuron disease, a disease almost entirely represented by ALS. One of these clusters was detected in the province of Novara (Piedmont, Northern Italy), and Briga Novarese municipality was the centroid of this area of 10 km of radius (Figure 1) (60).
Certainly, the investigated area is known for its strong metal contamination due to metallurgical plants area and particularly for taps production. Heavy metals coming from
discharged water of metallurgic activities had great impact on soil, surface water and groundwater quality in the investigated area (61).
We here report a further investigation of these findings, through the collection of recent incidence ALS data from Briga Novarese area, also to assess the possible involvement of environmental pollution in ALS etiology in that area.
Methods
Study area
The study area is the province of Novara, located in Piedmont region (Northern Italy) with an extension of 1,300 km2. During the study period, the population increased and varied from
340,000 persons in 2002 to up to 360,000 persons in 2012 with a population density of
approximately 270 inhabitants/km2. In the province of Novara there are five main municipalities,
Novara, the largest one with 100,000 inhabitants (inh), Trecate (20,000 inh), Galliate (16,000 inh) in the south, Borgomanero (22,000 inh) and Arona (14,000 inh) in the north, and other small towns with less than 3,000 inh. Generally, the land is flat in the south, mainly devoted to rice and corn production, other leading activities are industrial manufacturing and service industry. Furthermore in Trecate, surroundings at suburbs of Milan province, there is noticeable oil refinery. North is hilly and characterized by the presence of forests and vineyards. Finally, in the Southern area near Orta and Maggiore lakes, there are an intense cultivation of flowers into greenhouses and a great number of metallurgic plants, particularly specializing in the manufacture of taps (Figure 1).
In the investigated area, the number of tap production units increased from 69 in 1961 to 300 in 1991, respectively with 110 and 3083 workers and exports of more than 600 billion lire in 1994. Around 22% of workers were involved in tap production units, excluding the ‘home-work’ of family members (62). In the following years, the building crisis reduced demand but according Chamber of Commerce, Industry, Craft and Agriculture of Novara in 2010, in three main
municipalities of the investigated area, Gozzano, Briga novarese and Borgomanero, there were still respectively 56 (4,66/km2), 20 (4.2/km2) and 29 (0.9/km2) production units in the metalworking
sector (61).
Furthermore, until the ‘50, the taps production was carried out typically within artisanal enterprises, called “holes”, thanks to the presence of an ancient tradition linked to the processing of ferrous materials and assigning to women the task of preparation of souls for mergers at their own home (63).
Environmental pollution
There are several but fragmented data about the environmental pollutants of the investigated area. A study of Regional Agency for the Protection of Environment of Piedmont (ARPA) showed significant differences for concentrations of metals, especially for As, Sn, Pb and Zn, in soils of Briga area compared to Novara province and overall Piedmont region and indicate a common antropic origin (64). In the same area, there are 15 contaminated sites inscribed to the Regional Register resulting from uncontrolled discharges (e.g. metals and heavy metals) from the production units until the mid-90s (65). Specific studies on the water of upper aquifer of the contaminated sites showed concentrations of Al, Mn, Ni, Pb, total Cr beyond the limits of the D.Lgs. 152/2006 (66). Deeper groundwater intended for human consumption was under the mandatory limits of D.Lgs.31/2001 and D.Lgs.152/2006 and always distributed to the population (66, 67). Surface waters showed a poor condition or barely sufficient, always due to discharges from metallurgical industries in the past.
Data collection and analysis
In order to collect data of all incidence ALS cases in the province of Novara in the period 2002-2012, different databases have been consulted. Data from the registries of hospital discharge records (using 335.20 code of International Classification of Diseases 9 Clinical Modification - ICD-9-CM) have been collected from the two Hospital Neurology Departments of Novara and Veruno. Only probable and definite ALS cases according El Escorial-revised classification (68) have been extracted, along with clinical information and date of diagnosis.
We also consulted the Piemonte and Valle d'Aosta registry for ALS (PARALS) at the Regional Expert Center for ALS (CRESLA) at the University of Turin. Moreover, data from death certificates of the archives of Novara, Vercelli and Omegna Local Health Districts were collected in order to avoid loss of cases identification.
Indirect standardization was carried out considering the resident population from 2002 to 2012 and dividing it into five age classes (35-44, 45-54, 55-64, 65-74 and >75 years): the age-specific rates of "standard population", i.e. the resident population of the province of Novara excluding residents of the municipalities of the area under investigation, has been multiplied by the age-specific incidence rates of the study population, resulting in the number of cases expected in each age group. We also calculated the ratio between observed and expected cases, i.e. the Standardized Incidence Ratio (SIR). A SIR greater than 1 indicates that the incident cases are greater than expected.
This research was approved by the Ethics Committee of the University of Milan, and of the Ospedale Maggiore della Carità of Novara and the Fondazione Salvatore Maugeri Veruno. All data are presented in an anonymous form and only pooled data are reported. Finally data analyses were performed using software Excel (Office package 2010) and Stata (Version 13.1, Stata Corp. College Station, TX 2014).
Results
In the period from 2002 to 2012 in the province of Novara we identified 106 ALS cases from hospital discharge registers, crossed with data from death certificates (Table 1). In the whole province, we observed from 6 new cases of ALS in 2003 to 15 new cases in 2012, with a median value of 9 new cases per year and crude incidence rate of 2.5 cases/100,000 people. 35 subjects out of 106 cases were residents in the investigated area of Briga novarese, with 15 men and 20 women (43% vs. 57%, respectively), leading to a male to female ratio of 0.75, while 71 were living in the rest of the province of Novara, with 43 men and 28 women (61% vs. 39%, respectively) (Table 2), with a male to female ratio of 1.54 According to age groups, we identified an increasing number of cases with increasing age of classes. This trend is still evident for both sexes in the two areas, except for the age class greater than 75 years in the investigated area. The lowest number of cases were found in the 35-44 age class, both in the investigated area and in the rest of the province (Figure 2).
For the period 2002-2012, incidence rates of Novara province, standardized incidence rates with 95% Confidence Intervals (CI), number of observed and expected cases and SIR with 95% CI of the investigated area are reported for total population and by sex, stratified for age classes (Table 2). Incidence rates of Novara province were 3.98, 5.14 and 2.96 for total population, men and women, respectively. Standardized incidence rates were generally higher with values of 4.65, 4.27 and 4.98 for total population, men and women, respectively.
Stratifying by age groups, incidence rates and standardized incidence rates in the
investigated area showed high imprecision. In the total population, higher rates could be noted in the 45-54 age class (1.74 vs. 3.67) and in the 65-74 age class (6.31 vs. 10.73). Sex-specific analysis showed higher rates in men in the 45-54 age class (0.49 vs. 4.90), while in women higher values can be observed in 55-64 age class (2.85 vs. 3.98) and in the 65-74 age class (4.23 vs. 15.41). Figure 3 showed the incidence rates of Novara province and the standardized incidence rates in the
the period 2002-2012. Higher rates for men in the 45-54 age and for women in the 65-74 age class could also be noted.
Comparing number of expected to observed cases in the total population of Briga area, we found an excess of five cases (30 expected vs. 35 observed cases), mainly due to an excess in women (20 vs. 12 cases) than men (18 vs. 15 cases). SIR analysis showed a value of 1.17 (95% CI 0.81-1.62) for total population, with SIR respectively lower in men (0.83, 95% CI 0.47-1.37) and higher in women (1.68, 95% CI 1.03-2.60). When we stratified for age groups, we found SIR of 9.92 (95% CI 2.70-25.40) for men in the 45-54 age class and of 3.64 (95% CI 1.82-6.52) for women in the 65-74 age class, that corresponds to double or triple observed than expected cases in the investigated area, respectively.
Discussion
In this study, we investigated recent ALS incidence in an Italian province where severe environmental pollution due to industrial chemicals has occurred. Overall, the epidemiology of the disease in the entire province confirmed the widely observed age-related increase, despite our estimates were statistically imprecise (36, 41).
Previous studies in the same or neighboring Italian regions reported incidence of 3.46 (95% IC 2.83-4.20) in Novara Province and 3.41 (95% IC 3.22-3.60) in Piedmont Region in the period 1995-2004 (69), 3.22 (95% IC 2.66-3.90) in Liguria in 2009-2010 and male-female ratios were respectively 1.28 and 1.34 (70). In 2002-2012, incidence in the study area was 4.71 (95% IC 3.20-6.52) and male to female ratio 0.75, while in the rest of Novara Province incidence was 3.98 and male-female ratio 1.54. Generally, men present higher incidence than women, ranging from 2.97 vs 2.32 in Piedmont (71), and 3.71 vs 2.77 in Liguria (70). Similarly to other studies, incidence rate increased up to a pick in the 65-74 age class both in the investigated area and the province (70, 71).
The slightly higher incidence in women in the investigated area is conflicting with previous findings. A possible explanation could be found in the high exposure of women during processing
of taps at their home. The increasing urbanization and the economic boom since the ’50 allowed the consolidation and the expansion of some companies and the creation of new businesses by a process of budding, especially small family ones, traditionally women were involved in some particular phases in the tap manufacture that could be performed on their home, yielding to frequent dermal contact and inhalation of metal dust (62, 63).
Our results did not appear to confirm the presence of the previously described cluster of ALS in the study area and specifically in the area of Briga which was long term characterized by a severe degree of environmental pollution (60).
The study area showed statistically significant differences for As, Zn, Sn, Pb and Cu in soil compared to Novara Province and Piedmont region indicating a widespread anthropic
contamination. Furthermore, the presence of high concentration of As and Zn seems to address to a natural strong contribution and it could be explained by the presence of these two elements in the bedrock, but this hypothesis needs more studies. According to ‘Regional Program of Surveillance of Groundwater’, the samples collected in the period 2003-2008 did not show exceeding of metal concentrations over the regulatory limits in the water of the examined wells, with the exception of Pb (61). Nevertheless, all the other samples from deeper aquifer were always under the mandatory limits for water intended for human consumption (66, 67).
Specific studies on groundwater of the contaminated sites showed concentrations of Al, Mn, Ni, Pb, total Cr beyond the mandatory limits (61, 66). Before the remediation program started since the ‘90s for the widespread pollution, the contaminated sites within Briga municipality, namely Cascina Beatrice and the upstream areas, were characterized by a heavy contamination of soil and groundwater by metals such total Cr, Cu, Zn, and Ni. Even surface waters showed a poor condition or barely sufficient, always due to discharges from metallurgical industries in the past (61).
Nowadays, the water pollution clearly decreased, since wastewater are processed both by production units and by treatment plants (unpublished data).
However, another plausible interpretation of the lack of consistency between our results and the previously described cluster of ALS in the polluted area can be due to a more reliable and comprehensive methodology in case retrieval and ascertainment compared with the previous investigation based on ALS mortality only (60).
This study has some limitations. First, incidence estimates were generally imprecise due to small number of cases reduced did not allow to identify any reliable cluster of ALS in the
investigated area. However, the sample size was enough to allow the detection of a strongly
increased risk, should it has been as high as previously documented. Furthermore, the study design, which did not include collection of personal exposure data from each subjects, did not allow to clearly establish a causal relation between such environmental pollutants exposure and increase ALS risk.
Strengths of our study included the use of incidence rather than mortality data, and the use of the indirect standardization methods for ALS incidence estimation, considering the rarity of the disease, while the previous study was based on direct standardization.
Conclusion
In conclusion, our study does not confirm previous findings carried out on the same area and is still far from reaching definitive conclusions on causes or risk factors of ALS. Further investigation including a pollutants exposure assessment within the population residing in the area with severe environmental pollution should be performed to better address the issue of the possible environmental etiology of the ALS.
Table 1. Distribution of ALS cases from 2002 to 2012 according to the Health Districts of province of Novara.
Health District 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Total
Arona 3 0 1 2 0 1 3 4 2 0 5 21 Borgomanero 2 0 5 2 3 3 2 1 1 5 3 27 Galliate 3 2 1 0 0 2 0 0 1 1 2 12 Novara 0 3 4 4 5 3 1 3 4 6 5 38 VCO1 0 1 0 1 1 1 3 0 0 1 0 8 Total 8 6 11 9 9 10 9 8 8 13 15 106 1Verbano-Cusio-Ossola
Table 2. Incidence rates of Novara province and incidence rates with 95% Confidence Intervals (CI), number of observed and expected cases with Standardized Incidence Ratio (SIR) with 95% CI for the investigated area in the period 2002-2012. Data for total population and divided by men and women, stratified by age classes.
Age classes Inc. ratesNovara1 Area Inc. rates (95%CI)1 Observedcases Expectedcases SIR (95% CI)
Total 35-44 1.07 0.52 (0.00 - 3.01) 1 2.1 0.49 (0.01 - 2.72) 45-54 1.74 3.67 (1.32 - 8.05) 6 2.9 2.11 (0.77 - 4.59) 55-64 4.69 3.41 (1.08 - 8.03) 5 6.9 0.73 (0.24 - 1.70) 65-74 6.31 10.73 (5.85 - 18.06) 14 8.2 1.70 (0.93 - 2.86) >75 8.78 7.39 (3.35 - 14.10) 9 10.7 0.84 (0.39 - 1.60) Overall 3.98 4.65 (3.24 - 6.47) 35 30.0 1.17 (0.81 - 1.62) Men 35-44 2.11 1.02 (0.00 - 5.84) 1 2.1 0.49 (0.01 - 2.69) 45-54 0.49 4.9 (1.27 - 12.67) 4 0.4 9.92 (2.70 - 25.40) 55-64 6.63 2.81 (0.27 - 10.34) 2 4.7 0.42 (0.05 - 1.53) 65-74 8.84 5.08 (0.96 - 15.04) 3 5.2 0.58 (0.12 - 1.68) >75 14.62 12.1 (3.82 - 28.47) 5 6.0 0.83 (0.27 - 1.93) Overall 5.14 4.27 (2.38 - 7.06) 15 18.1 0.83 (0.47 - 1.37) Women 35-44 0 - 0 - -45-54 3.01 2.45 (0.23 - 9 .00) 2 2.5 0.81 (0.10 - 2.94) 55-64 2.85 3.98 (0.75 - 11.79) 3 2.2 1.40 (0.29 - 4.08) 65-74 4.23 15.41 (7.65 - 27.67) 11 3.0 3.64 (1.82 - 6.52) >75 5.63 4.97 (1.29 - 12.86) 4 4.5 0.88 (0.24 - 2.26) Overall 2.96 4.98 (3.04 - 7.71) 20 11.9 1.68 (1.03 - 2.60)
Figure 1: a) Province of Novara and Municipalities of the investigated area (yellow circle): Agrate Conturbia, Ameno, Armeno, Arona, Boca, Bogogno, Borgomanero, Briga Novarese, Cavallirio, Colazza, Comignago, Cressa, Cureggio, Dormelletto, Fontaneto d'Agogna, Gargallo, Gattico, Gozzano, Grignasco, Invorio, Maggiora, Meina, Miasino, Nebbiuno, Oleggio Castello, Orta San Giulio, Paruzzaro, Pella, Pettenasco, Pisano, Pogno, Prato Sesia, Romagnano Sesia, San Maurizio d'Opaglio, Veruno, Soriso. Area of Borgomanero (red circle) interested by the study on soil, groundwater quality of ARPA Piemonte 2010 (59) b) District of Taps in province of Novara (63)
Land use Lakes Rice field Other fields Urbanized area Forest
Yellow circle investigated area; Red circle: Area of Borgomanero interested by the study on soil, groundwater quality (ARPA Piemonte, 2010)
1.a
Figure 2. Number of cases of ALS for Novara province (black lines) and for the investigated area (gray lines) divided in age categories and for total population and by gender (long dash for males and short dash for females).
0 5 10 15 20 25 N u m be r o f c as e s 35-4 4 45-5 4 55-6 4 65-7 4 >75 Age classes Novara Investigated Area A - Total Cases 0 5 10 15 20 25 N u m be r o f c as e s 35-4 4 45-5 4 55-6 4 65-7 4 >75 Age classes Novara Investigated Area B - Men 0 5 10 15 20 25 N u m be r o f c as e s 35-4 4 45-5 4 55-6 4 65-7 4 >75 Age classes Novara Investigated Area C - Women
Figure 3. Incidence rates of Novara province and standardized incidence rates for investigated area in the period 2002-2012 for total population and by sex, stratified by age classes.
0 5 10 15 ca se s/ 1 00 .0 00 35-4 4 45-5 4 55-6 4 65-7 4 >75 Age classes Investigated area Standard A - Total 0 5 10 15 ca se s/ 1 00 .0 00 35-4 4 45-5 4 55-6 4 65-7 4 >75 Age classes Investigated area Standard B - Men 0 5 10 15 ca se s/ 1 00 .0 00 35-4 4 45-5 4 55-6 4 65-7 4 >75 Age classes Investigated area Standard C - Women
Incidence rates for investigated area and standard population
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